Mybatis分页如何实现?四种常用分页方式你Get到没！

﹏ヽ暗。殇╰゛Y 2023-01-21 02:11 31阅读 0赞

## 前言 ##

关于Mybatis的知识点总结了一个思维导图分享给大家

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzQ4Nzk1NjA3_size_16_color_FFFFFF_t_70_pic_center][]

### 数组分页 ###

查询出全部数据，然后再list中截取需要的部分。[2021面试题整理。][2021]

mybatis接口

List<Student> queryStudentsByArray();

xml配置文件

<select id="queryStudentsByArray"  resultMap="studentmapper">
            select * from student
     </select>

service

接口
    List<Student> queryStudentsByArray(int currPage, int pageSize);
    实现接口
     @Override
        public List<Student> queryStudentsByArray(int currPage, int pageSize) { 
            //查询全部数据
            List<Student> students = studentMapper.queryStudentsByArray();
            //从第几条数据开始
            int firstIndex = (currPage - 1) * pageSize;
            //到第几条数据结束
            int lastIndex = currPage * pageSize;
            return students.subList(firstIndex, lastIndex); //直接在list中截取
        }

controller

@ResponseBody  
@RequestMapping("/student/array/\{currPage\}/\{pageSize\}")  
public List getStudentByArray(@PathVariable(“currPage”) int currPage, @PathVariable(“pageSize”) int pageSize) \{  
List student = StuServiceIml.queryStudentsByArray(currPage, pageSize);  
return student;  
\}

### sql分页 ###

mybatis接口

List<Student> queryStudentsBySql(Map<String,Object> data);

xml文件

<select id="queryStudentsBySql" parameterType="map" resultMap="studentmapper">
            select * from student limit #{ currIndex} , #{ pageSize}
    </select>

service

接口
    List<Student> queryStudentsBySql(int currPage, int pageSize);
    实现类
    public List<Student> queryStudentsBySql(int currPage, int pageSize) { 
            Map<String, Object> data = new HashedMap();
            data.put("currIndex", (currPage-1)*pageSize);
            data.put("pageSize", pageSize);
            return studentMapper.queryStudentsBySql(data);
        }

### 拦截器分页 ###

创建拦截器，拦截mybatis接口方法id以ByPage结束的语句

package com.autumn.interceptor;
    
    import org.apache.ibatis.executor.Executor;
    import org.apache.ibatis.executor.parameter.ParameterHandler;
    import org.apache.ibatis.executor.resultset.ResultSetHandler;
    import org.apache.ibatis.executor.statement.StatementHandler;
    import org.apache.ibatis.mapping.MappedStatement;
    import org.apache.ibatis.plugin.*;
    import org.apache.ibatis.reflection.MetaObject;
    import org.apache.ibatis.reflection.SystemMetaObject;
    
    import java.sql.Connection;
    import java.util.Map;
    import java.util.Properties;
    
    /** * @Intercepts 说明是一个拦截器 * @Signature 拦截器的签名 * type 拦截的类型 四大对象之一( Executor,ResultSetHandler,ParameterHandler,StatementHandler) * method 拦截的方法 * args 参数,高版本需要加个Integer.class参数,不然会报错 */
    @Intercepts({ @Signature(type = StatementHandler.class, method = "prepare", args = { Connection.class})})
    public class MyPageInterceptor implements Interceptor { 
    
        //每页显示的条目数
        private int pageSize;
        //当前现实的页数
        private int currPage;
        //数据库类型
        private String dbType;
    
    
        @Override
        public Object intercept(Invocation invocation) throws Throwable { 
            //获取StatementHandler，默认是RoutingStatementHandler
            StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
            //获取statementHandler包装类
            MetaObject MetaObjectHandler = SystemMetaObject.forObject(statementHandler);
    
            //分离代理对象链
            while (MetaObjectHandler.hasGetter("h")) { 
                Object obj = MetaObjectHandler.getValue("h");
                MetaObjectHandler = SystemMetaObject.forObject(obj);
            }
    
            while (MetaObjectHandler.hasGetter("target")) { 
                Object obj = MetaObjectHandler.getValue("target");
                MetaObjectHandler = SystemMetaObject.forObject(obj);
            }
    
            //获取连接对象
            //Connection connection = (Connection) invocation.getArgs()[0];
    
    
            //object.getValue("delegate"); 获取StatementHandler的实现类
    
            //获取查询接口映射的相关信息
            MappedStatement mappedStatement = (MappedStatement) MetaObjectHandler.getValue("delegate.mappedStatement");
            String mapId = mappedStatement.getId();
    
            //statementHandler.getBoundSql().getParameterObject();
    
            //拦截以.ByPage结尾的请求，分页功能的统一实现
            if (mapId.matches(".+ByPage$")) { 
                //获取进行数据库操作时管理参数的handler
                ParameterHandler parameterHandler = (ParameterHandler) MetaObjectHandler.getValue("delegate.parameterHandler");
                //获取请求时的参数
                Map<String, Object> paraObject = (Map<String, Object>) parameterHandler.getParameterObject();
                //也可以这样获取
                //paraObject = (Map<String, Object>) statementHandler.getBoundSql().getParameterObject();
    
                //参数名称和在service中设置到map中的名称一致
                currPage = (int) paraObject.get("currPage");
                pageSize = (int) paraObject.get("pageSize");
    
                String sql = (String) MetaObjectHandler.getValue("delegate.boundSql.sql");
                //也可以通过statementHandler直接获取
                //sql = statementHandler.getBoundSql().getSql();
    
                //构建分页功能的sql语句
                String limitSql;
                sql = sql.trim();
                limitSql = sql + " limit " + (currPage - 1) * pageSize + "," + pageSize;
    
                //将构建完成的分页sql语句赋值个体'delegate.boundSql.sql'，偷天换日
                MetaObjectHandler.setValue("delegate.boundSql.sql", limitSql);
            }
            //调用原对象的方法，进入责任链的下一级
            return invocation.proceed();
        }
    
    
        //获取代理对象
        @Override
        public Object plugin(Object o) { 
            //生成object对象的动态代理对象
            return Plugin.wrap(o, this);
        }
    
        //设置代理对象的参数
        @Override
        public void setProperties(Properties properties) { 
            //如果项目中分页的pageSize是统一的，也可以在这里统一配置和获取，这样就不用每次请求都传递pageSize参数了。参数是在配置拦截器时配置的。
            String limit1 = properties.getProperty("limit", "10");
            this.pageSize = Integer.valueOf(limit1);
            this.dbType = properties.getProperty("dbType", "mysql");
        }
    }

配置文件SqlMapConfig.xml

mybatis配置

List<AccountExt> getAllBookByPage(@Param("currPage")Integer pageNo,@Param("pageSize")Integer pageSize);
    
      <sql id="getAllBooksql" >
        acc.id, acc.cateCode, cate_name, user_id,u.name as user_name, money, remark, time
      </sql>
      <select id="getAllBook" resultType="com.autumn.pojo.AccountExt" >
        select
        <include refid="getAllBooksql" />
        from account as acc
      </select>

service

java
        public List<AccountExt> getAllBookByPage(String pageNo,String pageSize) { 
            return accountMapper.getAllBookByPage(Integer.parseInt(pageNo),Integer.parseInt(pageSize));
        }

controller

@RequestMapping("/getAllBook")
    @ResponseBody
    public Page getAllBook(String pageNo,String pageSize,HttpServletRequest request,HttpServletResponse response){ 
        pageNo=pageNo==null?"1":pageNo;   //当前页码
        pageSize=pageSize==null?"5":pageSize;   //页面大小
        //获取当前页数据
        List<AccountExt> list = bookService.getAllBookByPage(pageNo,pageSize);
        //获取总数据大小
        int totals = bookService.getAllBook();
        //封装返回结果
        Page page = new Page();
        page.setTotal(totals+"");
        page.setRows(list);
        return page;
    }

Page实体类

package com.autumn.pojo;
    
    import java.util.List;
    
    /** * Created by Autumn on 2018/6/21. */
    public class Page { 
        private String pageNo = null;
        private String pageSize = null;
        private String total = null;
        private List rows = null;
    
        public String getTotal() { 
            return total;
        }
    
        public void setTotal(String total) { 
            this.total = total;
        }
    
        public List getRows() { 
            return rows;
        }
    
        public void setRows(List rows) { 
            this.rows = rows;
        }
    
        public String getPageNo() { 
            return pageNo;
        }
    
        public void setPageNo(String pageNo) { 
            this.pageNo = pageNo;
        }
    
        public String getPageSize() { 
            return pageSize;
        }
    
        public void setPageSize(String pageSize) { 
            this.pageSize = pageSize;
        }
    
    }

前端

bootstrap-table接受数据格式
    
    复制代码
    { 
      "total": 3,
      "rows": [
        { 
          "id": 0,
          "name": "Item 0",
          "price": "$0"
        },
        { 
          "id": 1,
          "name": "Item 1",
          "price": "$1"
        }
      ]
    }

boostrap-table用法

### RowBounds分页 ###

数据量小时，RowBounds不失为一种好办法。但是数据量大时，实现拦截器就很有必要了。

mybatis接口加入RowBounds参数

public List queryUsersByPage(String userName, RowBounds rowBounds);

service

@Override
        @Transactional(isolation = Isolation.READ_COMMITTED, propagation = Propagation.SUPPORTS)
        public List<RoleBean> queryRolesByPage(String roleName, int start, int limit) { 
            return roleDao.queryRolesByPage(roleName, new RowBounds(start, limit));
        }

## 最后 ##

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