Element组件，Servlet优化，批量删除，分页查询，条件查询，动态SQL

比眉伴天荒 2024-03-27 13:21 67阅读 0赞

**目录**

一、Element概述

二、Element快速入门

三、Element布局

四、Element组件

五、综合案例

5.1 查询所有

5.2 新增品牌

5.3 Servlet代码优化

5.4 修改品牌

5.5 删除品牌

5.6 批量删除

5.7 分页查询

5.8 条件查询

--------------------

## 一、Element概述 ##

![cd9ebdf4e6444ac0b03a9283d03108bc.png][]

## 二、Element快速入门 ##

## ![de170357a0c244eab2c79711baead422.png][] ##

## 三、Element布局 ##

![0e6616493aa4400e8dbc7530c59c36c1.png][]

## 四、Element组件 ##

![6550a26fe89d405480897012795cb2b7.png][]

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Title</title>
    
        
        <style>
            .el-table .warning-row {
                background: oldlace;
            }
    
            .el-table .success-row {
                background: #f0f9eb;
            }
        </style>
    
    </head>
    <body>
    <div id="app">
    
        
        <el-form :inline="true" :model="brand" class="demo-form-inline">
    
            <el-form-item label="当前状态">
                <el-select v-model="brand.status" placeholder="当前状态">
                    <el-option label="启用" value="1"></el-option>
                    <el-option label="禁用" value="0"></el-option>
                </el-select>
            </el-form-item>
    
            <el-form-item label="企业名称">
                <el-input v-model="brand.companyName" placeholder="企业名称"></el-input>
            </el-form-item>
    
            <el-form-item label="品牌名称">
                <el-input v-model="brand.brandName" placeholder="品牌名称"></el-input>
            </el-form-item>
    
            <el-form-item>
                <el-button type="primary" @click="onSubmit">查询</el-button>
            </el-form-item>
        </el-form>
    
        
        <el-row>
            <el-button type="danger" plain disabled>批量删除</el-button>
            <el-button type="primary" plain  @click="dialogVisible = true">新增</el-button>
        </el-row>
    
        
        <el-dialog
                title="编辑品牌"
                :visible.sync="dialogVisible"
                width="30%">
            <el-form ref="form" :model="brand" label-width="80px">
    
                <el-form-item label="品牌名称">
                    <el-input v-model="brand.brandName"></el-input>
                </el-form-item>
    
                <el-form-item label="企业名称">
                    <el-input v-model="brand.companyName"></el-input>
                </el-form-item>
    
                <el-form-item label="排序">
                    <el-input v-model="brand.ordered"></el-input>
                </el-form-item>
    
                <el-form-item label="备注">
                    <el-input type="textarea" v-model="brand.description"></el-input>
                </el-form-item>
    
                <el-form-item label="状态">
                    <el-switch v-model="brand.status"
                               active-value="1"
                               inactive-value="0"
                    ></el-switch>
                </el-form-item>
    
                <el-form-item>
                    <el-button type="primary" @click="addBrand">提交</el-button>
                    <el-button @click="dialogVisible = false">取消</el-button>
                </el-form-item>
            </el-form>
        </el-dialog>
    
        
        <template>
            <el-table
                    :data="tableData"
                    style="width: 100%"
                    :row-class-name="tableRowClassName"
                    @selection-change="handleSelectionChange">
                
                <el-table-column
                        type="selection"
                        width="55">
                </el-table-column>
                
                <el-table-column
                        type="index"
                        width="50">
                </el-table-column>
    
                <el-table-column
                        prop="brandName"
                        label="品牌名称"
                        align="center">
                </el-table-column>
                <el-table-column
                        prop="companyName"
                        label="企业名称"
                        align="center">
                </el-table-column>
                <el-table-column
                        prop="ordered"
                        label="排序"
                        align="center">
                </el-table-column>
                <el-table-column
                        prop="status"
                        label="当前状态"
                        align="center">
                </el-table-column>
    
                <el-table-column
                        label="操作"
                        align="center">
                    <el-row>
                        <el-button type="primary">修改</el-button>
                        <el-button type="danger">删除</el-button>
                    </el-row>
                </el-table-column>
    
            </el-table>
        </template>
    
        
        <el-pagination
                @size-change="handleSizeChange"
                @current-change="handleCurrentChange"
                :current-page="currentPage"
                :page-sizes="[5, 10, 15, 20]"
                :page-size="5"
                layout="total, sizes, prev, pager, next, jumper"
                :total="400">
        </el-pagination>
    
    </div>
    
    
    <script src="js/vue.js"></script>
    <script src="element-ui/lib/index.js"></script>
    <link rel="stylesheet" href="element-ui/lib/theme-chalk/index.css">
    
    <script>
        new Vue({
            el: "#app",
            methods: {
                tableRowClassName({row, rowIndex}) {
                    if (rowIndex === 1) {
                        return 'warning-row';
                    } else if (rowIndex === 3) {
                        return 'success-row';
                    }
                    return '';
                },
    
                //复选框选中后执行的方法
                handleSelectionChange(val) {
                    this.multipleSelection = val;
                    /*打印*/
                    console.log(this.multipleSelection)
                },
    
                //查询方法
                onSubmit() {
                    console.log(this.brand);
                },
    
                //添加数据
                addBrand(){
                    console.log(this.brand);
                },
                handleSizeChange(val) {
                    console.log(`每页 ${val} 条`);
                },
                handleCurrentChange(val) {
                    console.log(`当前页: ${val}`);
                }
            },
            data() {
                return {
                    //当前页码
                    currentPage: 4,
    
                    //添加数据对话框是否展示的标记
                    dialogVisible:false,
    
                    //品牌模型数据
                    brand: {
                        status: '',
                        brandName: '',
                        companyName: '',
                        id:"",
                        ordered:"",
                        description:""
                    },
    
                    //复选框选中数据集合
                    multipleSelection: [],
    
                    //表格数据
                    tableData: [{
                        brandName: '华为',
                        companyName: '华为科技有限公司',
                        ordered: '100',
                        status:'1'
                    }, {
                        brandName: '华为',
                        companyName: '华为科技有限公司',
                        ordered: '100',
                        status:'1'
                    }, {
                        brandName: '华为',
                        companyName: '华为科技有限公司',
                        ordered: '100',
                        status:'1'
                    }, {
                        brandName: '华为',
                        companyName: '华为科技有限公司',
                        ordered: '100',
                        status:'1'
                    }]
                }
            }
        })
    
    </script>
    
    </body>
    </html>

## 五、综合案例 ##

![5dc00e4e888f4e65817a799860a73b9d.png][]

### 5.1 查询所有 ###

![fb38ef99340149c18e931c35e5cec108.png][]

**Dao层：**

Mapper接口:

public interface BrandMapper {
    
        /**
         * 查询所有
         * @return
         */
        @Select("select * from tb_brand")
        @ResultMap("brandResultMap")
        List<Brand> selectAll();
    
    }

BrandMapper.xlm:

brand实体类:

package com.itheima.pojo;
    
    public class Brand {
        // id 主键
        private Integer id;
        // 品牌名称
        private String brandName;
        // 企业名称
        private String companyName;
        // 排序字段
        private Integer ordered;
        // 描述信息
        private String description;
        // 状态：0：禁用  1：启用
        private Integer status;
    
    
        public Integer getId() {
            return id;
        }
    
        public void setId(Integer id) {
            this.id = id;
        }
    
        public String getBrandName() {
            return brandName;
        }
    
        public void setBrandName(String brandName) {
            this.brandName = brandName;
        }
    
        public String getCompanyName() {
            return companyName;
        }
    
        public void setCompanyName(String companyName) {
            this.companyName = companyName;
        }
    
        public Integer getOrdered() {
            return ordered;
        }
    
        public void setOrdered(Integer ordered) {
            this.ordered = ordered;
        }
    
        public String getDescription() {
            return description;
        }
    
        public void setDescription(String description) {
            this.description = description;
        }
    
        public Integer getStatus() {
            return status;
        }
        //逻辑视图
        public String getStatusStr(){
            if (status == null){
                return "未知";
            }
            return status == 0 ? "禁用":"启用";
        }
    
        public void setStatus(Integer status) {
            this.status = status;
        }
    
        @Override
        public String toString() {
            return "Brand{" +
                    "id=" + id +
                    ", brandName='" + brandName + '\'' +
                    ", companyName='" + companyName + '\'' +
                    ", ordered=" + ordered +
                    ", description='" + description + '\'' +
                    ", status=" + status +
                    '}';
        }
    }

**Service层**

BrandService接口：

public interface BrandService {
        /**
         * 查询所有
         * @return
         */
        List<Brand> selectAll();
    
    }

接口实现类：

public class BrandServiceImpl implements BrandService {
        //1.创建SqlSessionFactory工厂对象
        SqlSessionFactory factory = SqlSessionFactoryUtils.getSqlSessionFactory();
    
    
        @Override
        public List<Brand> selectAll() {
    
             //2.获取SqlSession对象
            SqlSession sqlSession = factory.openSession();
    
            //3.获取BrandMapper
            BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
    
            //4.调用方法
            List<Brand> brands = mapper.selectAll();
    
            //5.释放资源
            sqlSession.close();
    
            return brands;
        }
    }

**Web层**

Servlet：

@WebServlet("/selectAllServlet")
    public class SelectAllServlet extends HttpServlet {
    
        private BrandService brandService = new BrandServiceImpl();
    
    
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
            //1.调用service查询
            List<Brand> brands = brandService.selectAll();
    
            //2.将数据转为JSON
            String jsonString = JSON.toJSONString(brands);
    
            //3.写数据
            response.setContentType("text/json;charset=utf-8");
            response.getWriter().write(jsonString);
        }
    
        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            this.doGet(request, response);
        }
    }

Vue：

mounted(){
                //当页面加载完成后，发送异步请求来获取数据
                var _this = this;
                axios({
                    method:"get",
                    url:"http://localhost:8080/brand-case/selectAllServlet"
                }).then(function (resp){
                    _this.tableData = resp.data;
                })
    
            }

### 5.2 新增品牌 ###

![7ee351b7d5fa4ac1ad51322e4303cfa9.png][]

**Dao层**

BrandMapper接口：

/**
         * 添加数据
         * @param brand
         */
        @Insert("insert into tb_brand values(null,#{brandName},#{companyName},#{ordered},#{description},#{status})")
        void add(Brand brand);

**Service层**

service接口：

/**
         * 添加品牌数据
         * @param brand
         */
        void add(Brand brand);

service接口实现方法：

@Override
        public void add(Brand brand) {
            //2.获取SqlSession对象
            SqlSession sqlSession = factory.openSession();
    
            //3.获取BrandMapper
            BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
    
            //4.调用方法
            mapper.add(brand);
    
            //5.提交事务
            sqlSession.commit();
    
            //6.释放资源
            sqlSession.close();
        }

**Web层**

AddServlet类：

@WebServlet("/addServlet")
    public class AddServlet extends HttpServlet {
    
        private BrandService brandService = new BrandServiceImpl();
    
    
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
            //1.接受品牌数据
            BufferedReader br = request.getReader();
            String params = br.readLine();//json字符串
    
            //转为Brand对象
            Brand brand = JSON.parseObject(params, Brand.class);
    
            //2.调用service添加
            brandService.add(brand);
    
            //3.响应成功的标识
            response.getWriter().write("success");
    
        }
    
        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            this.doGet(request, response);
        }
    }

Vue：

//查询所有数据
                selectAll(){
                    //当页面加载完成后，发送异步请求来获取数据
                    var _this = this;
                    axios({
                        method:"get",
                        url:"http://localhost:8080/brand-case/selectAllServlet"
                    }).then(function (resp){
                        _this.tableData = resp.data;
                    })
                }

// 添加数据
                addBrand(){
                    //console.log(this.brand);
                    var _this = this;
                    //发送ajax请求，添加数据
                    axios({
                        method:"post",
                        url:"http://localhost:8080/brand-case/addServlet",
                        data:_this.brand
                    }).then(function (resp){
                        if(resp.data == "success"){
                            //添加成功
    
                            //关闭窗口
                            _this.dialogVisible = false;
    
                            //重新查询数据
                            _this.selectAll();
    
                            //弹出消息提示
                            _this.$message({
                                showClose: true,
                                message: '恭喜你，添加成功',
                                type: 'success'
                            });
                        }
                    })
    
                }

### 5.3 Servlet代码优化 ###

![938784afb56f411ca854312bf48b3437.png][]

BaseServlet：

package com.itheima.web.servlet;
    
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;
    
    /**
     * 替换HtttpServlet,根据请求的最后一段路径，进行方法分发
     */
    
    public class BaseServlet extends HttpServlet {
    
        //根据资源路径进行方法分发
        @Override
        protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            //1.获取请求路径
            String requestURI = req.getRequestURI();//URI="/brand-case/brand/selectAll"
    
            //2.获取最后一段路径
            int index = requestURI.lastIndexOf("/");//从后面开始找，找到第一个出现字符为"/"并截取其后的字符串（包含/）
            String methodName = requestURI.substring(index+1);//select
    
            //3.执行方法
            //3.1获取BrandService/UserService 字节码对象 .class
                //谁调用我（this所在的方法），我(this)代表谁
                //this代表BrandServlet
            Class<? extends BaseServlet> cls = this.getClass();
    
            //3.2获取方法Method对象
            try {
                Method method = cls.getMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);
                //3.3执行方法
                method.invoke(this, req,resp);
            } catch (NoSuchMethodException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
    
    
        }
    }

BrandServlet：

@WebServlet("/brand/*")
    public class BrandServlet extends BaseServlet{
    
        private BrandService brandService = new BrandServiceImpl();
    
        public void selectAll(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //1.调用service查询
            List<Brand> brands = brandService.selectAll();
    
            //2.将数据转为JSON
            String jsonString = JSON.toJSONString(brands);
    
            //3.写数据
            response.setContentType("text/json;charset=utf-8");
            response.getWriter().write(jsonString);
        }
        public void add(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
            //1.接受品牌数据
            BufferedReader br = request.getReader();
            String params = br.readLine();//json字符串
    
            //转为Brand对象
            Brand brand = JSON.parseObject(params, Brand.class);
    
            //2.调用service添加
            brandService.add(brand);
    
            //3.响应成功的标识
            response.getWriter().write("success");
        }
    }

### 5.4 修改品牌 ###

### 5.5 删除品牌 ###

**Dao层**

/**
         * 根据id删除
         * @param id
         */
        @Delete("delete from tb_brand where id = #{id}")
        void deleteById(int id);

**Service层**

BrandService接口：

/**
         * 单个删除
         * @param id
         */
        void deleteById(int id);

BrandMapper实现类：

@Override
        public void deleteById(int id) {
            //2.获取SqlSession对象
            SqlSession sqlSession = factory.openSession();
    
            //3.获取BrandMapper
            BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
    
            //4.调用方法
            mapper.deleteById(id);
    
            //5.提交事务
            sqlSession.commit();
    
            //6.释放资源
            sqlSession.close();
        }

**Web层**

BrandServlet：

/**
         * 单个删除
         * @param request
         * @param response
         * @throws ServletException
         * @throws IOException
         */
        public void deleteById(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
            //1.获取要删除的id，获取data中的数据
            BufferedReader br = request.getReader();
            String _id = br.readLine();//json字符串
    
            System.out.println(_id);
            //转为int数据
            int id = JSON.parseObject(_id,int.class);
    
            //2.调用service添加
            brandService.deleteById(id);
    
            //3.响应成功的标识
            response.getWriter().write("success");
        }

前端:

<el-row slot-scope="scope">
          <el-button type="danger" @click="deleteById(scope.row)">删除</el-button>
     </el-row>

// 单个删除
                deleteById(row){
                    //弹出确认的提示框
                    this.$confirm('此操作将永久删除该数据, 是否继续?', '提示', {
                        confirmButtonText: '确定',
                        cancelButtonText: '取消',
                        type: 'warning'
                    }).then(() => {
                        //用户点击确认按钮
                        //1.获取id
                        var _this = this;
                        //发送ajax请求，添加数据
                        axios({
                            method:"post",
                            url:"http://localhost:8080/brand-case/brand/deleteById",
                            data:row.id
                        }).then(function (resp){
                            if(resp.data == "success"){
                                //删除成功
                                //重新查询数据
                                _this.selectAll();
                                //弹出消息提示
                                _this.$message({
                                    showClose: true,
                                    message: '恭喜你，删除成功',
                                    type: 'success'
                                });
                            }
                        })
                    }).catch(() => {
                        //用户点击取消按钮
                        this.$message({
                            type: 'info',
                            message: '已取消删除'
                        });
                    });
                },

根据id删除可以采用Post，也可以采用Get，上述为采用post提交方式，通过data传递id数据

以下为采用get方式：

**BrandServlet**中需要修改

//1.获取要删除的id，获取data中的数据
            BufferedReader br = request.getReader();
            String _id = br.readLine();//json字符串
    
            System.out.println(_id);
            //转为int数据
            int id = JSON.parseObject(_id,int.class);

为：

//1.获取要删除的id，获取data中的数据
            String _id = request.getParameter("id");
    
            //转为int数据
            int id = Integer.parseInt(_id);

**前端页面**中：修改

axios({
           method:"post",
           url:"http://localhost:8080/brand-case/brand/deleteById",
           data:row.id
         })

为

axios({
           method:"get",
           url:"http://localhost:8080/brand-case/brand/deleteById?id="+row.id
          })

补充知识：

用到显示表格时,当前行数据的获取也会用到插槽，例如

<el-table>
    	<el-table-column width="150" align="center" label="Status">
            <template slot-scope="scope">
              <el-tag :type="scope.row.status | statusFilter">{
       {scope.row.status}}</el-tag>
            </template>
          </el-table-column>
      </el-table>

scope相当于一行的数据， scope.row相当于当前行的数据对象。这里就是用插槽 拿到当前行 row是个内置的属性 ，vue slot的scope传递值是父作用域中的源数据改变，值会同步改变。且\{ \{scope.$index\}\}可以获取当前行的index。

<slot :row="item" :$index="i"></slot>//index可以用来设置index   :row 可以设置行内内置对象

### 5.6 批量删除 ###

![b224846a323341aabd7870b2401df848.png][]

**Dao层**

BrandMapper接口:

/**
         * 批量删除
         * @param ids
         */
        void deleteByIds(@Param("ids") int[] ids);

BrandMapper.xml:

<delete id="deleteByIds">
            delete from tb_brand where id in
            <foreach collection="ids" item="id" separator="," open="(" close=")">
                #{id}
            </foreach>
        </delete>

**Service层**

BrandMapper接口:

/**
         * 批量删除
         * @param ids
         */
        void deleteByIds(int[] ids);

BrandMapper实现接口：

@Override
        public void deleteByIds(int[] ids) {
            //2.获取SqlSession对象
            SqlSession sqlSession = factory.openSession();
    
            //3.获取BrandMapper
            BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
    
            //4.调用方法
            mapper.deleteByIds(ids);
    
            //5.提交事务
            sqlSession.commit();
    
            //6.释放资源
            sqlSession.close();
        }

**Web层**

BrandServlet:

/**
         * 批量删除
         * @param request
         * @param response
         * @throws ServletException
         * @throws IOException
         */
        public void deleteByIds(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
            //1.接受品牌数据,Json格式[1,2,3]
            BufferedReader br = request.getReader();
            String params = br.readLine();//json字符串
    
            //转为int数据
            int[] ids = JSON.parseObject(params, int[].class);
    
            //2.调用service添加
            brandService.deleteByIds(ids);
    
            //3.响应成功的标识
            response.getWriter().write("success");
        }

Vue:

方法：

// 批量删除
                deleteByIds(){
    
                    //弹出确认的提示框
                    this.$confirm('此操作将永久删除该数据, 是否继续?', '提示', {
                        confirmButtonText: '确定',
                        cancelButtonText: '取消',
                        type: 'warning'
                    }).then(() => {
                        //用户点击确认按钮
    
                        //1.创建id数组[1,2,3]，从this.multipleSelection获取即可
                        for (let i = 0; i < this.multipleSelection.length; i++) {
                            //定义一个对象数组接收multipleSelection[i]对象
                            //let selectionElement = this.multipleSelection[i];
                            this.selectedIds[i] = this.multipleSelection[i].id;
                        }
                        var _this = this;
                        //发送ajax请求，添加数据
                        axios({
                            method:"post",
                            url:"http://localhost:8080/brand-case/brand/deleteByIds",
                            data:_this.selectedIds
                        }).then(function (resp){
                            if(resp.data == "success"){
    
                                //删除成功
                                //重新查询数据
                                _this.selectAll();
    
                                //弹出消息提示
                                _this.$message({
                                    showClose: true,
                                    message: '恭喜你，删除成功',
                                    type: 'success'
                                });
                            }
                        })
                    }).catch(() => {
                        //用户点击取消按钮
                        this.$message({
                            type: 'info',
                            message: '已取消删除'
                        });
                    });
                }

数据：

//被选中的id数组
                    selectedIds:[],

### 5.7 分页查询 ###

![aa091648d5db47d5bae2252619ebf19b.png][]

-- 分页查询 limit
    -- 参数1:开始查询的索引
    -- 参数2:查询的条目数
    
    select * from tb_brand limit 0,5
    
    select * from tb_brand limit 5,5
    
    
    -- 页面传递的参数
    -- 当前页码
    -- 每页显示的条数
    
    -- 参数1:开始索引 = (当前页码-1) * 每页显示条数
    -- 参数2:查询的条目数 = 每页显示条数

PageBean实体类:

package com.itheima.pojo;
    
    
    import java.util.List;
    
    //分页查询的JavaBean
    public class PageBean <T>{
    
        //总记录数
       private int totalCount;
    
       //当前页数据,自定义泛型<T>
        private List<T> rows;
    
        public int getTotalCount() {
            return totalCount;
        }
    
        public void setTotalCount(int totalCount) {
            this.totalCount = totalCount;
        }
    
        public List<T> getRows() {
            return rows;
        }
    
        public void setRows(List<T> rows) {
            this.rows = rows;
        }
        
    }

![9b2e813c7ca54d18b9352c02d9c493df.png][]

**Dao层**

BrandMapper 接口:

/**
         * 分页查询
         * @param begin
         * @param size
         * @return
         */
        @Select("select * from tb_brand limit #{begin},#{size}")
        @ResultMap("brandResultMap")
        List<Brand> selectByPage(@Param("begin") int begin,@Param("size")int size);
    
        /**
         * 查询总记录数
         * @return
         */
        @Select("select count(*) from tb_brand")
        int selectTotalCount();

**Service层:**

BrandService接口：

/**
         * 分页查询
         * @param currentPage  当前页码
         * @param pageSize   每页展示条数
         * @return
         */
        PageBean<Brand> selectByPage(int currentPage,int pageSize);

BrandService实现类：

@Override
        public PageBean<Brand> selectByPage(int currentPage, int pageSize) {
            //2.获取SqlSession对象
            SqlSession sqlSession = factory.openSession();
    
            //3.获取BrandMapper
            BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
    
            //4.计算开始索引
            int begin = ( currentPage - 1) * pageSize;
            //计算查询条目数
            int size = pageSize;
    
            //5.查询当前页数据
            List<Brand> rows = mapper.selectByPage(begin, size);
    
            //6.查询总记录数
            int totalCount = mapper.selectTotalCount();
    
            //7.封装PageBean对象
            PageBean<Brand> pageBean = new PageBean<>();
            pageBean.setRows(rows);
            pageBean.setTotalCount(totalCount);
    
            //8.释放资源
            sqlSession.close();
    
            return pageBean;
        }

**Web层：**

BrandServlet:

/**
         * 分页查询
         * @param request
         * @param response
         * @throws ServletException
         * @throws IOException
         */
        public void selectByPage(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //1.接受 当前页码 和 每页展示条数  url?currentPage=1&pageSize=5
            String _currentPage = request.getParameter("currentPage");
            String _pageSize = request.getParameter("pageSize");
            //转为int类型
            int currentPage = Integer.parseInt(_currentPage);
            int pageSize = Integer.parseInt(_pageSize);
    
            //2.调用service查询
            PageBean<Brand> pageBean = brandService.selectByPage(currentPage, pageSize);
    
            //2.将数据转为JSON
            String jsonString = JSON.toJSONString(pageBean);
    
            //3.写数据
            response.setContentType("text/json;charset=utf-8");
            response.getWriter().write(jsonString);
    
        }

Vue:

//查询分页数据
                selectAll(){
                    var _this = this;
                    axios({
                        method:"get",
                        //拼字符串，换成模型，使之变为动态数据
                    url:"http://localhost:8080/brand-case/brand/selectByPage?currentPage="+_this.currentPage+"&pageSize="+_this.pageSize
                    }).then(function (resp){
                        //设置表格数据
                        _this.tableData = resp.data.rows;//{rows:[],totalCount:100}
                        //设置总记录数
                        _this.totalCount = resp.data.totalCount;
                        console.log(_this.totalCount );
    
    
                    })
                }

//分页
                handleSizeChange(val) {
                    //console.log(`每页 ${val} 条`);
                    //重新设置每页显示的条数
                    this.pageSize = val;
                    this.selectAll();
                }
                handleCurrentChange(val) {
                    //console.log(`当前页: ${val}`);
                    //重新设置当前页码
                    this.currentPage = val;
                    this.selectAll();
                }

数据：

//每页显示的条数
                    pageSize:5,//默认
                    //总记录数
                    totalCount:100,//默认
                    // 当前页码
                    currentPage: 1,//默认

### 5.8 条件查询 ###

![d44f6c6c52c84c29bbe82c45379462de.png][]

![ea3f11ebca184287baa364375f56bed2.png][]

**Dao层**

BrandMapper接口：

/**
         * 分页条件查询
         * @param begin
         * @param size
         * @param brand
         * @return
         */
        List<Brand> selectByPageAndCondition(@Param("begin") int begin,@Param("size")int size,@Param("brand")Brand brand);
    
        /**
         * 根据条件查询总记录数
         * @return
         */
        int selectTotalCountByCondition(Brand brand);

BrandMapper.xml:

<select id="selectByPageAndCondition" resultMap="brandResultMap">
            select *
            from tb_brand
            <where>
                <if test="brand.brandName != null and brand.brandName != '' ">
                    and brand_name like #{brand.brandName}
                </if>
    
                <if test="brand.companyName != null and brand.companyName != '' ">
                    and company_name like #{brand.companyName}
                </if>
    
                <if test="brand.status != null">
                    and status like #{brand.status}
                </if>
            </where>
    
            limit #{begin},#{size}
    
        </select>
    
    
        
        <select id="selectTotalCountByCondition" resultType="java.lang.Integer">
            select count(*)
            from tb_brand
            <where>
                <if test="brandName != null and brandName != '' ">
                    and brand_name like #{brandName}
                </if>
    
                <if test="companyName != null and companyName != '' ">
                    and company_name like #{companyName}
                </if>
    
                <if test="status != null">
                    and status like #{status}
                </if>
            </where>
        </select>

**Service层**

BrandService接口:

/**
         * 分页条件查询
         * @param currentPage
         * @param pageSize
         * @param brand
         * @return
         */
        PageBean<Brand> selectByPageAndCondition(int currentPage,int pageSize,Brand brand);

BrandService实现类:

@Override
        public PageBean<Brand> selectByPageAndCondition(int currentPage, int pageSize, Brand brand) {
            //2.获取SqlSession对象
            SqlSession sqlSession = factory.openSession();
    
            //3.获取BrandMapper
            BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
    
            //4.计算开始索引
            int begin = ( currentPage - 1) * pageSize;
            //计算查询条目数
            int size = pageSize;
    
    
            //处理brand条件,模糊表达式
            String brandName = brand.getBrandName();
            if (brandName != null && brandName.length() > 0) {
                brand.setBrandName("%" + brandName + "%");
            }
    
            String companyName = brand.getCompanyName();
            if (companyName != null && companyName.length() > 0) {
                brand.setCompanyName("%" + companyName + "%");
            }
    
            //5.查询当前页数据
            List<Brand> rows = mapper.selectByPageAndCondition(begin, size,brand);
    
            //6.查询总记录数
            int totalCount = mapper.selectTotalCountByCondition(brand);
    
            //7.封装PageBean对象
            PageBean<Brand> pageBean = new PageBean<>();
            pageBean.setRows(rows);
            pageBean.setTotalCount(totalCount);
    
            //8.释放资源
            sqlSession.close();
    
            return pageBean;
        }

**Web层**

BrandServlet:

/**
         * 分页条件查询
         * @param request
         * @param response
         * @throws ServletException
         * @throws IOException
         */
        public void selectByPageAndCondition(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //1.接受 当前页码 和 每页展示条数  url?currentPage=1&pageSize=5
            String _currentPage = request.getParameter("currentPage");
            String _pageSize = request.getParameter("pageSize");
            //转为int类型
            int currentPage = Integer.parseInt(_currentPage);
            int pageSize = Integer.parseInt(_pageSize);
    
            //获取对应的查询条件对象
            BufferedReader br = request.getReader();
            String params = br.readLine();//json字符串
    
            //转为Brand
            Brand brand = JSON.parseObject(params, Brand.class);
    
            //2.调用service查询
            PageBean<Brand> pageBean = brandService.selectByPageAndCondition(currentPage, pageSize,brand);
    
            System.out.println(pageBean);
            //2.将数据转为JSON
            String jsonString = JSON.toJSONString(pageBean);
    
            //3.写数据
            response.setContentType("text/json;charset=utf-8");
            response.getWriter().write(jsonString);
    
        }

Vue:

//查询分页数据
                selectAll(){
                   /* //当页面加载完成后，发送异步请求来获取数据
                    var _this = this;
                    axios({
                        method:"get",
                        url:"http://localhost:8080/brand-case/brand/selectAll"
                    }).then(function (resp){
                        //console.log(resp.data);
                        _this.tableData = resp.data;
                    })*/
                    var _this = this;
                    axios({
                        method:"post",
                        //拼字符串，换成模型，使之变为动态数据
                        url:"http://localhost:8080/brand-case/brand/selectByPageAndCondition?currentPage="+this.currentPage+"&pageSize="+this.pageSize,
                        data:this.brand//请求体数据json类型
                    }).then(function (resp){
                        //设置表格数据
                        _this.tableData = resp.data.rows;//{rows:[],totalCount:100}
                        //设置总记录数
                        _this.totalCount = resp.data.totalCount;
                        //console.log(_this.totalCount );
                    })
                }

前端代码优化："=>"后可直接用this来表示vue对象

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Title</title>
        <style>
            .el-table .warning-row {
                background: oldlace;
            }
    
            .el-table .success-row {
                background: #f0f9eb;
            }
        </style>
    
    </head>
    <body>
    <div id="app">
    
        
        <el-form :inline="true" :model="brand" class="demo-form-inline">
    
            <el-form-item label="当前状态">
                <el-select v-model="brand.status" placeholder="当前状态">
                    <el-option label="启用" value="1"></el-option>
                    <el-option label="禁用" value="0"></el-option>
                </el-select>
            </el-form-item>
    
            <el-form-item label="企业名称">
                <el-input v-model="brand.companyName" placeholder="企业名称"></el-input>
            </el-form-item>
    
            <el-form-item label="品牌名称">
                <el-input v-model="brand.brandName" placeholder="品牌名称"></el-input>
            </el-form-item>
    
            <el-form-item>
                <el-button type="primary" @click="onSubmit">查询</el-button>
            </el-form-item>
        </el-form>
    
        
        <el-row>
            <el-button type="danger" plain @click="deleteByIds">批量删除</el-button>
            <el-button type="primary" plain @click="dialogVisible = true">新增</el-button>
        </el-row>
    
        
        <el-dialog
                title="编辑品牌"
                :visible.sync="dialogVisible"
                width="30%"
                >
    
            <el-form ref="form" :model="brand" label-width="80px">
                <el-form-item label="品牌名称">
                    <el-input v-model="brand.brandName"></el-input>
                </el-form-item>
    
                <el-form-item label="企业名称">
                    <el-input v-model="brand.companyName"></el-input>
                </el-form-item>
    
                <el-form-item label="排序">
                    <el-input v-model="brand.ordered"></el-input>
                </el-form-item>
    
                <el-form-item label="备注">
                    <el-input type="textarea" v-model="brand.description"></el-input>
                </el-form-item>
    
                <el-form-item label="状态">
                    <el-switch v-model="brand.status"
                               active-value="1"
                               inactive-value="0"
                    ></el-switch>
                </el-form-item>
    
    
                <el-form-item>
                    <el-button type="primary" @click="addBrand">提交</el-button>
                    <el-button @click="dialogVisible = false">取消</el-button>
                </el-form-item>
            </el-form>
    
        </el-dialog>
    
    
        
        <template>
            <el-table
                    :data="tableData"
                    style="width: 100%"
                    :row-class-name="tableRowClassName"
                    @selection-change="handleSelectionChange"
            >
                <el-table-column
                        type="selection"
                        width="55">
                </el-table-column>
    
                <el-table-column
                        type="index"
                        width="50">
                </el-table-column>
    
                <el-table-column
                        prop="brandName"
                        label="品牌名称"
                        align="center"
                >
                </el-table-column>
                <el-table-column
                        prop="companyName"
                        label="企业名称"
                        align="center"
                >
                </el-table-column>
                <el-table-column
                        prop="ordered"
                        align="center"
                        label="排序">
                </el-table-column>
                <el-table-column
                        prop="statusStr"
                        align="center"
                        label="当前状态">
                </el-table-column>
    
                <el-table-column
                        align="center"
                        label="操作">
    
                    <el-row>
                        <el-button type="primary">修改</el-button>
                        <el-button type="danger">删除</el-button>
                    </el-row>
    
                </el-table-column>
    
            </el-table>
        </template>
    
        
        <el-pagination
                @size-change="handleSizeChange"
                @current-change="handleCurrentChange"
                :current-page="currentPage"
                :page-sizes="[5, 10, 15, 20]"
                :page-size="5"
                layout="total, sizes, prev, pager, next, jumper"
                :total="totalCount">
        </el-pagination>
    
    </div>
    
    
    <script src="js/vue.js"></script>
    <script src="js/axios-0.18.0.js"></script>
    <script src="element-ui/lib/index.js"></script>
    <link rel="stylesheet" href="element-ui/lib/theme-chalk/index.css">
    
    
    <script>
        new Vue({
            el: "#app",
    
    
            /*加载完成后*/
            mounted(){
                //当页面加载完成后，发送异步请求来获取数据
                this.selectAll();
                /*var _this = this;
                axios({
                    method:"get",
                    url:"http://localhost:8080/brand-case/selectAllServlet"
                }).then(function (resp){
                    _this.tableData = resp.data;
                })*/
    
    
            },
    
    
            /*方法区*/
            methods: {
    
                //查询分页数据
                selectAll(){
                   /* //当页面加载完成后，发送异步请求来获取数据
                    var _this = this;
                    axios({
                        method:"get",
                        url:"http://localhost:8080/brand-case/brand/selectAll"
                    }).then(function (resp){
                        //console.log(resp.data);
                        _this.tableData = resp.data;
                    })*/
    
                    /*var _this = this;
                    axios({
                        method:"post",
                        //拼字符串，换成模型，使之变为动态数据
                        url:"http://localhost:8080/brand-case/brand/selectByPageAndCondition?currentPage="+this.currentPage+"&pageSize="+this.pageSize,
                        data:this.brand//请求体数据json类型
                    }).then(function (resp){
                        //设置表格数据
                        _this.tableData = resp.data.rows;//{rows:[],totalCount:100}
                        //设置总记录数
                        _this.totalCount = resp.data.totalCount;
                        //console.log(_this.totalCount );
                    })*/
                    var _this = this;
                    axios({
                        method:"post",
                        //拼字符串，换成模型，使之变为动态数据
                        url:"http://localhost:8080/brand-case/brand/selectByPageAndCondition?currentPage="+this.currentPage+"&pageSize="+this.pageSize,
                        data:this.brand//请求体数据json类型
                    }).then(resp =>{
                        //设置表格数据
                        this.tableData = resp.data.rows;//{rows:[],totalCount:100}
                        //设置总记录数
                        this.totalCount = resp.data.totalCount;
                    })
    
                },
    
                tableRowClassName({row, rowIndex}) {
                    if (rowIndex === 1) {
                        return 'warning-row';
                    } else if (rowIndex === 3) {
                        return 'success-row';
                    }
                    return '';
                },
    
                // 复选框选中后执行的方法
                handleSelectionChange(val) {
                    this.multipleSelection = val;
                    //console.log(this.multipleSelection)
                },
    
                // 查询方法
                onSubmit() {
                    //console.log(this.brand);
                    this.selectAll();
                },
    
                // 添加数据
                addBrand(){
                    //console.log(this.brand);
                    var _this = this;
                    //发送ajax请求，添加数据
                    axios({
                        method:"post",
                        url:"http://localhost:8080/brand-case/brand/add",
                        data:_this.brand
                    }).then(function (resp){
                        if(resp.data == "success"){
                            //添加成功
    
                            //关闭窗口
                            _this.dialogVisible = false;
    
                            //重新查询数据
                            _this.selectAll();
    
                            //弹出消息提示
                            _this.$message({
                                showClose: true,
                                message: '恭喜你，添加成功',
                                type: 'success'
                            });
                        }
                    })
                },
    
    
                // 批量删除
                deleteByIds(){
                    //弹出确认的提示框
                    this.$confirm('此操作将永久删除该数据, 是否继续?', '提示', {
                        confirmButtonText: '确定',
                        cancelButtonText: '取消',
                        type: 'warning'
                    }).then(() => {
                        //用户点击确认按钮
                        //1.创建id数组[1,2,3]，从this.multipleSelection获取即可
                        for (let i = 0; i < this.multipleSelection.length; i++) {
                            //定义一个对象数组接收multipleSelection[i]对象
                            //let selectionElement = this.multipleSelection[i];
                            this.selectedIds[i] = this.multipleSelection[i].id;
                        }
                        var _this = this;
                        //发送ajax请求，添加数据
                        axios({
                            method:"post",
                            url:"http://localhost:8080/brand-case/brand/deleteByIds",
                            data:_this.selectedIds
                        }).then(function (resp){
                            if(resp.data == "success"){
                                //删除成功
                                //重新查询数据
                                _this.selectAll();
                                //弹出消息提示
                                _this.$message({
                                    showClose: true,
                                    message: '恭喜你，删除成功',
                                    type: 'success'
                                });
                            }
                        })
                    }).catch(() => {
                        //用户点击取消按钮
                        this.$message({
                            type: 'info',
                            message: '已取消删除'
                        });
                    });
                },
    
                //分页
                handleSizeChange(val) {
                    //console.log(`每页 ${val} 条`);
                    //重新设置每页显示的条数
                    this.pageSize = val;
                    this.selectAll();
                },
                handleCurrentChange(val) {
                    //console.log(`当前页: ${val}`);
                    //重新设置当前页码
                    this.currentPage = val;
                    this.selectAll();
                },
            },
    
    
            /*数据区*/
            data() {
                return {
                    //每页显示的条数
                    pageSize:5,
                    //总记录数
                    totalCount:100,
                    // 当前页码
                    currentPage: 1,
                    // 添加数据对话框是否展示的标记
                    dialogVisible: false,
    
                    // 品牌模型数据
                    brand: {
                        status: '',
                        brandName: '',
                        companyName: '',
                        id:"",
                        ordered:"",
                        description:""
                    },
    
                    //被选中的id数组
                    selectedIds:[],
    
                    // 复选框选中数据集合
                    multipleSelection: [],
    
                    // 表格数据
                    tableData: []
                }
            }
        })
    
    </script>
    
    </body>
    </html>

[cd9ebdf4e6444ac0b03a9283d03108bc.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/d1d68cbc379b4b6184f1ff3eba74eac9.png
[de170357a0c244eab2c79711baead422.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/111900b69fbb4566a1daa89c08b06b56.png
[0e6616493aa4400e8dbc7530c59c36c1.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/a9f11d4fbabe4c8b83d2f5735196b703.png
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