MyBatis分页插件－PageHelper的配置与应用(二):即插即用的PageInfo<T>

悠悠 2022-06-04 05:41 336阅读 0赞

*  MyBatis分页插件PageHelper的配置与应用
    
     *  一引入PageHelper依赖
     *  二配置拦截器插件
     *  三使用分页插件
        
         *  mapper接口 简单易懂
         *  mapperxml 框架已做好处理
            
             *  Service类 服务MV C
             *  JUnit 测试类
     *  总结
     *  参考封装PageInfo类

在我看来，这个分页插件为mybatis量身定制。完美融合框架,一句多余的代码也不需要我们写.我们

# MyBatis分页插件－PageHelper的配置与应用 #

## 一.引入PageHelper依赖 ##

pom.xml 引入依赖:

<dependency>
        <groupId>com.github.pagehelper</groupId>
        <artifactId>pagehelper</artifactId>
        <version>5.1.2</version>
    </dependency>
    
    <dependency>
        <groupId>com.github.jsqlparser</groupId>
        <artifactId>jsqlparser</artifactId>
        <version>0.9.5</version>
    </dependency>

\*如果不用maven需要自行下载两个jar包:

1.  [http://repo1.maven.org/maven2/com/github/pagehelper/pagehelper/][http_repo1.maven.org_maven2_com_github_pagehelper_pagehelper]
2.  [http://repo1.maven.org/maven2/com/github/jsqlparser/jsqlparser/0.9.5/][http_repo1.maven.org_maven2_com_github_jsqlparser_jsqlparser_0.9.5]

## 二.配置拦截器插件 ##

**spring-mybatis.xml** 集成配置:

<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource" />
        
        <property name="mapperLocations" value="classpath:site/gaoyisheng/mapping/*.xml"></property>
    
        
        <property name="plugins">
            <array>
                <bean class="com.github.pagehelper.PageInterceptor">
                    <property name="properties">
                        
                        <value>
                              helperDialect=postgresql
                              reasonable=true
                              supportMethodsArguments=true
                              params=count=countSql
                              autoRuntimeDialect=true
                        </value>
                    </property>
                </bean>
            </array>
        </property>
    </bean>

简单介绍其中参数,具体参数详见:[ 分页插件参数介绍][Link 1]

*  **helperDialect**:如果不配置,pagehelper会自动获取连接，检测数据库。也可以自己声明数据库的方言，比如此处用的postgresql。
 *  **reasonable**:配置pageNum参数合理化，比如第0页，和超过最后一页，则返会第一页和最后一页。而不是意想不到的数据。
 *  **supportMethodsArguments**:”支持通过 Mapper 接口参数来传递分页参数”,通过interface传给mapper.xml，默认false不支持.代码实例可见 例子:[查询测试代码][Link 2] , [mapper.xml代码][mapper.xml],查看详细的写法.展示了两种不同传值方法,
 *  **params**=count=countSql 为了支持PageHelper.startPage(Object params)方法,默认值为pageNum=pageNum;pageSize=pageSize;count=countSql;reasonable=reasonable;pageSizeZero=pageSizeZero .
 *  **autoRuntimeDialect**:运行时多数据源(数据库)自动识别，默认值false。true则允许自动识别对应方言的分页.

至此,我们已经配好一个简单可用的分页插件了.

## 三.使用分页插件 ##

这里介绍其中一种方法,简单易懂.

### 1.**mapper接口** 简单易懂 ###

最简单的使用方法是,通过mapper接口,传递分页参数:

/** * . * TODO 查看所有未认领的awards * @param request * @return */
        @RequestMapping(value = "/notClaimed-list", method = RequestMethod.POST)
        @ResponseBody
        public Object notClaimedList(HttpServletRequest request) {
    
            int pageNum = Integer.valueOf(request.getParameter("pageNum"));
            int pageSize = Integer.valueOf(request.getParameter("pageSize"));
    
            //注意,查询语句要紧跟下面这一条. 
            PageHelper.startPage(pageNum,pageSize);
            List<ChPeriodicalThesis> ls = chPeriodicalThesisService.selectByStatus("未认领");
    
            //返回PageInfo的JSON
            return new PageInfo<ChPeriodicalThesis>(ls);
    
        }

**pageNum**: 控制页数.  
**pageSize**: 控制页面大小.

### 2.**mapper.xml** 框架已做好处理 ###

在mapper.xml中,并不需要我们处理任何参数.\{“pageNum”,”pageSize”\} Mybatis框架会自动查找对应分页的数据然后返回.

<select id="selectByStatus" resultMap="BaseResultMap">
        select
            <include refid="Base_Column_List" />
        from en_periodical_thesis e
        where e.claim_status = #{status}
    </select>

不管你信不信,有了框架它就是这么方便.已经可以用了.我们再写个Service类和测试类跑跑看.

#### 3. **Service类** 服务MV **C** ####

/** * . * TODO 通过认领状态查询,+分页参数:重载 * @param status * @param pageNum * @param pageSize * @return */
        public List<EnPeriodicalThesis> selectByStatus(String claimStatus) {
            return thesisDao.selectByStatus(claimStatus);
        }

#### 3.**JUnit 测试类** ####

@Test
        public void pageHelperTest() {
    
            PageHelper.startPage(2,10);
            List<ChPeriodicalThesis> ls = chService.selectAll();
    
            PageInfo<ChPeriodicalThesis> pageInfo = new PageInfo<ChPeriodicalThesis>(ls);
    
            System.out.println("当前页:" + pageInfo.getPageNum());
            System.out.println("每页的数量:"+pageInfo.getPageSize());
            System.out.println("当前页的数量:"+pageInfo.getSize());
    
            //由于startRow和endRow不常用，这里说个具体的用法
            //可以在页面中"显示startRow到endRow 共size条数据"
    
            //当前页面第一个元素在数据库中的行号
            //当前页面最后一个元素在数据库中的行号
            System.out.println("显示"+pageInfo.getStartRow()+"到"+pageInfo.getEndRow() +"共"+pageInfo.getSize()+"条数据");
    
            System.out.println("当前页面第一个元素在数据库中的行号: "+pageInfo.getStartRow()); 
            System.out.println("当前页面最后一个元素在数据库中的行号: "+pageInfo.getEndRow());
            System.out.println("总记录数: "+pageInfo.getTotal());
            System.out.println("总页数: "+pageInfo.getPages());
    
            System.out.println("前一页："+pageInfo.getPrePage());
            System.out.println("下一页:"+pageInfo.getNextPage());
            System.out.println("是否为第一页:"+pageInfo.isIsFirstPage());
            System.out.println("是否为最后一页:"+pageInfo.isIsLastPage());
            System.out.println("是否有前一页:"+pageInfo.isHasPreviousPage());
            System.out.println("是否有下一页:"+pageInfo.isHasNextPage());
    
            System.out.println("导航页码数:"+pageInfo.getNavigatePages());
    
            System.out.println("所有导航页码数:");
            for(int i :  pageInfo.getNavigatepageNums()) {
                System.out.println(" "+i+",");
            }
    
        }

查询结果:

*  查询状态”未认领”
 *  第1页
 *  每页2条数据

DEBUG   - JDBC Connection [jdbc:postgresql://127.0.0.1:5432/trans, UserName=postgres, PostgreSQL JDBC Driver] will not be managed by Spring
    DEBUG   - ==>  Preparing: SELECT count(0) FROM ch_periodical_thesis 
    DEBUG   - ==> Parameters: 
    DEBUG   - <==      Total: 1
    DEBUG   - ==>  Preparing: select id, key_id, provenance, year, ministry, period, name, key_words, all_auther_name, mechanism,  claim_status from ch_periodical_thesis LIMIT ? OFFSET ? 
    DEBUG   - ==> Parameters: 10(Integer), 10(Integer)
    DEBUG   - <==      Total: 10
    DEBUG   - Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7caa550]
    DEBUG   - Returning JDBC Connection to DataSource
    
    当前页:2
    每页的数量:10
    当前页的数量:10
    显示11到20共10条数据
    当前页面第一个元素在数据库中的行号: 11
    当前页面最后一个元素在数据库中的行号: 20
    总记录数: 21582
    总页数: 2159
    前一页：1
    下一页:3
    是否为第一页:false
    是否为最后一页:false
    是否有前一页:true
    是否有下一页:true
    导航页码数:8
    所有导航页码数:
     1,
     2,
     3,
     4,
     5,
     6,
     7,
     8,

## 总结: ##

好用,简单易上手.

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

参考资料:

*  [https://pagehelper.github.io/][https_pagehelper.github.io]
 *  [https://pagehelper.github.io/docs/howtouse/\#1-%E5%BC%95%E5%85%A5%E5%88%86%E9%A1%B5%E6%8F%92%E4%BB%B6][https_pagehelper.github.io_docs_howtouse_1-_E5_BC_95_E5_85_A5_E5_88_86_E9_A1_B5_E6_8F_92_E4_BB_B6]

源码见:

*  [https://github.com/pagehelper/Mybatis-PageHelper][https_github.com_pagehelper_Mybatis-PageHelper]
 *  [https://github.com/abel533/Mybatis-Spring][https_github.com_abel533_Mybatis-Spring]

个人项目源码路径:欢迎交流指教.

*  [https://github.com/timo1160139211/trans][https_github.com_timo1160139211_trans]

本文链接:欢迎交流指教.

*  [http://blog.csdn.net/timo1160139211/article/details/78632831][http_blog.csdn.net_timo1160139211_article_details_78632831]

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

## 参考封装PageInfo类 ##

/* * The MIT License (MIT) * * Copyright (c) 2014-2017 abel533@gmail.com * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */
    
    package com.github.pagehelper;
    
    import java.io.Serializable;
    import java.util.Collection;
    import java.util.List;
    
    /** * 对Page<E>结果进行包装 * <p/> * 新增分页的多项属性，主要参考:http://bbs.csdn.net/topics/360010907 * * @author liuzh/abel533/isea533 * @version 3.3.0 * @since 3.2.2 * 项目地址 : http://git.oschina.net/free/Mybatis_PageHelper */
    @SuppressWarnings({
       "rawtypes", "unchecked"})
    public class PageInfo<T> implements Serializable {
        private static final long serialVersionUID = 1L;
        //当前页
        private int pageNum;
        //每页的数量
        private int pageSize;
        //当前页的数量
        private int size;
    
        //由于startRow和endRow不常用，这里说个具体的用法
        //可以在页面中"显示startRow到endRow 共size条数据"
    
        //当前页面第一个元素在数据库中的行号
        private int startRow;
        //当前页面最后一个元素在数据库中的行号
        private int endRow;
        //总记录数
        private long total;
        //总页数
        private int pages;
        //结果集
        private List<T> list;
    
        //前一页
        private int prePage;
        //下一页
        private int nextPage;
    
        //是否为第一页
        private boolean isFirstPage = false;
        //是否为最后一页
        private boolean isLastPage = false;
        //是否有前一页
        private boolean hasPreviousPage = false;
        //是否有下一页
        private boolean hasNextPage = false;
        //导航页码数
        private int navigatePages;
        //所有导航页号
        private int[] navigatepageNums;
        //导航条上的第一页
        private int navigateFirstPage;
        //导航条上的最后一页
        private int navigateLastPage;
    
        public PageInfo() {
        }
    
        /** * 包装Page对象 * * @param list */
        public PageInfo(List<T> list) {
            this(list, 8);
        }
    
        /** * 包装Page对象 * * @param list page结果 * @param navigatePages 页码数量 */
        public PageInfo(List<T> list, int navigatePages) {
            if (list instanceof Page) {
                Page page = (Page) list;
                this.pageNum = page.getPageNum();
                this.pageSize = page.getPageSize();
    
                this.pages = page.getPages();
                this.list = page;
                this.size = page.size();
                this.total = page.getTotal();
                //由于结果是>startRow的，所以实际的需要+1
                if (this.size == 0) {
                    this.startRow = 0;
                    this.endRow = 0;
                } else {
                    this.startRow = page.getStartRow() + 1;
                    //计算实际的endRow（最后一页的时候特殊）
                    this.endRow = this.startRow - 1 + this.size;
                }
            } else if (list instanceof Collection) {
                this.pageNum = 1;
                this.pageSize = list.size();
    
                this.pages = this.pageSize > 0 ? 1 : 0;
                this.list = list;
                this.size = list.size();
                this.total = list.size();
                this.startRow = 0;
                this.endRow = list.size() > 0 ? list.size() - 1 : 0;
            }
            if (list instanceof Collection) {
                this.navigatePages = navigatePages;
                //计算导航页
                calcNavigatepageNums();
                //计算前后页，第一页，最后一页
                calcPage();
                //判断页面边界
                judgePageBoudary();
            }
        }
    
        /** * 计算导航页 */
        private void calcNavigatepageNums() {
            //当总页数小于或等于导航页码数时
            if (pages <= navigatePages) {
                navigatepageNums = new int[pages];
                for (int i = 0; i < pages; i++) {
                    navigatepageNums[i] = i + 1;
                }
            } else { //当总页数大于导航页码数时
                navigatepageNums = new int[navigatePages];
                int startNum = pageNum - navigatePages / 2;
                int endNum = pageNum + navigatePages / 2;
    
                if (startNum < 1) {
                    startNum = 1;
                    //(最前navigatePages页
                    for (int i = 0; i < navigatePages; i++) {
                        navigatepageNums[i] = startNum++;
                    }
                } else if (endNum > pages) {
                    endNum = pages;
                    //最后navigatePages页
                    for (int i = navigatePages - 1; i >= 0; i--) {
                        navigatepageNums[i] = endNum--;
                    }
                } else {
                    //所有中间页
                    for (int i = 0; i < navigatePages; i++) {
                        navigatepageNums[i] = startNum++;
                    }
                }
            }
        }
    
        /** * 计算前后页，第一页，最后一页 */
        private void calcPage() {
            if (navigatepageNums != null && navigatepageNums.length > 0) {
                navigateFirstPage = navigatepageNums[0];
                navigateLastPage = navigatepageNums[navigatepageNums.length - 1];
                if (pageNum > 1) {
                    prePage = pageNum - 1;
                }
                if (pageNum < pages) {
                    nextPage = pageNum + 1;
                }
            }
        }
    
        /** * 判定页面边界 */
        private void judgePageBoudary() {
            isFirstPage = pageNum == 1;
            isLastPage = pageNum == pages || pages == 0;;
            hasPreviousPage = pageNum > 1;
            hasNextPage = pageNum < pages;
        }
    
        public int getPageNum() {
            return pageNum;
        }
    
        public void setPageNum(int pageNum) {
            this.pageNum = pageNum;
        }
    
        public int getPageSize() {
            return pageSize;
        }
    
        public void setPageSize(int pageSize) {
            this.pageSize = pageSize;
        }
    
        public int getSize() {
            return size;
        }
    
        public void setSize(int size) {
            this.size = size;
        }
    
        public int getStartRow() {
            return startRow;
        }
    
        public void setStartRow(int startRow) {
            this.startRow = startRow;
        }
    
        public int getEndRow() {
            return endRow;
        }
    
        public void setEndRow(int endRow) {
            this.endRow = endRow;
        }
    
        public long getTotal() {
            return total;
        }
    
        public void setTotal(long total) {
            this.total = total;
        }
    
        public int getPages() {
            return pages;
        }
    
        public void setPages(int pages) {
            this.pages = pages;
        }
    
        public List<T> getList() {
            return list;
        }
    
        public void setList(List<T> list) {
            this.list = list;
        }
    
        @Deprecated
        // firstPage就是1, 此函数获取的是导航条上的第一页, 容易产生歧义
        public int getFirstPage() {
            return navigateFirstPage;
        }
    
        @Deprecated
        public void setFirstPage(int firstPage) {
            this.navigateFirstPage = firstPage;
        }
    
        public int getPrePage() {
            return prePage;
        }
    
        public void setPrePage(int prePage) {
            this.prePage = prePage;
        }
    
        public int getNextPage() {
            return nextPage;
        }
    
        public void setNextPage(int nextPage) {
            this.nextPage = nextPage;
        }
    
        @Deprecated
        // 请用getPages()来获取最后一页, 此函数获取的是导航条上的最后一页, 容易产生歧义.
        public int getLastPage() {
            return navigateLastPage;
        }
    
        @Deprecated
        public void setLastPage(int lastPage) {
            this.navigateLastPage = lastPage;
        }
    
        public boolean isIsFirstPage() {
            return isFirstPage;
        }
    
        public void setIsFirstPage(boolean isFirstPage) {
            this.isFirstPage = isFirstPage;
        }
    
        public boolean isIsLastPage() {
            return isLastPage;
        }
    
        public void setIsLastPage(boolean isLastPage) {
            this.isLastPage = isLastPage;
        }
    
        public boolean isHasPreviousPage() {
            return hasPreviousPage;
        }
    
        public void setHasPreviousPage(boolean hasPreviousPage) {
            this.hasPreviousPage = hasPreviousPage;
        }
    
        public boolean isHasNextPage() {
            return hasNextPage;
        }
    
        public void setHasNextPage(boolean hasNextPage) {
            this.hasNextPage = hasNextPage;
        }
    
        public int getNavigatePages() {
            return navigatePages;
        }
    
        public void setNavigatePages(int navigatePages) {
            this.navigatePages = navigatePages;
        }
    
        public int[] getNavigatepageNums() {
            return navigatepageNums;
        }
    
        public void setNavigatepageNums(int[] navigatepageNums) {
            this.navigatepageNums = navigatepageNums;
        }
    
        public int getNavigateFirstPage() {
            return navigateFirstPage;
        }
    
        public int getNavigateLastPage() {
            return navigateLastPage;
        }
    
        public void setNavigateFirstPage(int navigateFirstPage) {
            this.navigateFirstPage = navigateFirstPage;
        }
    
        public void setNavigateLastPage(int navigateLastPage) {
            this.navigateLastPage = navigateLastPage;
        }
    
        @Override
        public String toString() {
            final StringBuffer sb = new StringBuffer("PageInfo{");
            sb.append("pageNum=").append(pageNum);
            sb.append(", pageSize=").append(pageSize);
            sb.append(", size=").append(size);
            sb.append(", startRow=").append(startRow);
            sb.append(", endRow=").append(endRow);
            sb.append(", total=").append(total);
            sb.append(", pages=").append(pages);
            sb.append(", list=").append(list);
            sb.append(", prePage=").append(prePage);
            sb.append(", nextPage=").append(nextPage);
            sb.append(", isFirstPage=").append(isFirstPage);
            sb.append(", isLastPage=").append(isLastPage);
            sb.append(", hasPreviousPage=").append(hasPreviousPage);
            sb.append(", hasNextPage=").append(hasNextPage);
            sb.append(", navigatePages=").append(navigatePages);
            sb.append(", navigateFirstPage=").append(navigateFirstPage);
            sb.append(", navigateLastPage=").append(navigateLastPage);
            sb.append(", navigatepageNums=");
            if (navigatepageNums == null) sb.append("null");
            else {
                sb.append('[');
                for (int i = 0; i < navigatepageNums.length; ++i)
                    sb.append(i == 0 ? "" : ", ").append(navigatepageNums[i]);
                sb.append(']');
            }
            sb.append('}');
            return sb.toString();
        }
    }

[http_repo1.maven.org_maven2_com_github_pagehelper_pagehelper]: http://repo1.maven.org/maven2/com/github/pagehelper/pagehelper/
[http_repo1.maven.org_maven2_com_github_jsqlparser_jsqlparser_0.9.5]: http://repo1.maven.org/maven2/com/github/jsqlparser/jsqlparser/0.9.5/
[Link 1]: https://pagehelper.github.io/docs/howtouse/#2-%E9%85%8D%E7%BD%AE%E6%8B%A6%E6%88%AA%E5%99%A8%E6%8F%92%E4%BB%B6
[Link 2]: https://github.com/pagehelper/Mybatis-PageHelper/blob/master/src/test/java/com/github/pagehelper/test/basic/ArgumentsObjTest.java
[mapper.xml]: https://github.com/pagehelper/Mybatis-PageHelper/blob/master/src/test/resources/com/github/pagehelper/mapper/CountryMapper.xml
[https_pagehelper.github.io]: https://pagehelper.github.io/
[https_pagehelper.github.io_docs_howtouse_1-_E5_BC_95_E5_85_A5_E5_88_86_E9_A1_B5_E6_8F_92_E4_BB_B6]: https://pagehelper.github.io/docs/howtouse/#1-%E5%BC%95%E5%85%A5%E5%88%86%E9%A1%B5%E6%8F%92%E4%BB%B6
[https_github.com_pagehelper_Mybatis-PageHelper]: https://github.com/pagehelper/Mybatis-PageHelper
[https_github.com_abel533_Mybatis-Spring]: https://github.com/abel533/Mybatis-Spring
[https_github.com_timo1160139211_trans]: https://github.com/timo1160139211/trans
[http_blog.csdn.net_timo1160139211_article_details_78632831]: http://blog.csdn.net/timo1160139211/article/details/78632831