关于Mybatis的pagehelper使用遇到的坑

参考博客: https://blog.csdn.net/wzyxdwll/article/details/66473466

下面给出pagehelp使用的配置, 在springmvc中的配置:

下面是maven中配置pagehelp:

<!-- https://mvnrepository.com/artifact/com.github.pagehelper/pagehelper -->
<dependency>
   <groupId>com.github.pagehelper</groupId>
   <artifactId>pagehelper</artifactId>
   <version>5.1.2</version>  <!--我这里用的是5.1.2版本-->
</dependency>

下面是spring-mybatis.xml的配置文件:

<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <property name="mapperLocations" value="classpath:com/demo/mapping/*.xml"></property>
        <property name="configLocation" value="classpath:conf/mybatis-config.xml"></property>
</bean>

下面是mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING" />
        <setting name="cacheEnabled" value="true" />
    </settings>
    <typeAliases>
        <typeAlias alias="Blog" type="com.demo.pojo.Blog" />
    </typeAliases>
    <plugins>
        <!--注意这里要写成PageInterceptor, 5.0之前的版本都是写PageHelper, 5.0之后要换成PageInterceptor-->
        <plugin interceptor="com.github.pagehelper.PageInterceptor">
            <!--<property name="helperDialect" value="mysql" />-->
            <property name="reasonable" value="true" />
        </plugin>
    </plugins>
</configuration>

下面是BlogMapper.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.demo.dao.BlogMapper" >
  <cache eviction="FIFO" flushInterval="60000" size="512" readOnly="true" />
  <resultMap id="BaseResultMap" type="com.demo.pojo.Blog" >
    <id column="id" property="id" jdbcType="INTEGER" />
    <result column="authorid" property="authorid" jdbcType="INTEGER" />
    <result column="title" property="title" jdbcType="VARCHAR" />
    <result column="creattime" property="creattime" jdbcType="VARCHAR" />
  </resultMap>
  <resultMap id="ResultMapWithBLOBs" type="com.demo.pojo.Blog" extends="BaseResultMap" >
    <result column="mainbody" property="mainbody" jdbcType="LONGVARCHAR" />
  </resultMap>
  <select id="selectAllByList" resultMap="ResultMapWithBLOBs">
       select
  <include refid="Base_Column_List" />
    ,
  <include refid="Blob_Column_List" />
    from blog
  </select>
</mapper>

下面是BlogMapper.java:

package com.demo.dao;
import com.demo.pojo.Blog;
public interface BlogMapper {
    //注意这里返回的类型是List, 而我们在BlogMapper.xml中写的返回类型是ResultMapWithBLOBs类型
    List<Blog> selectAllByList();
}

下面是BlogService.java:

package com.demo.service;
import java.util.List;
import java.util.Map;
import javax.annotation.Resource;
import org.springframework.stereotype.Service;
import com.demo.dao.BlogMapper;
import com.demo.pojo.Blog;
@Service(value="blogService")
public class BlogService {
    @Resource
    private BlogMapper blogMapper;
    public List<Blog> selectBlogByList() {
        List<Blog> blog = this.blogMapper.selectAllByList();
        return blog;
    }
}

下面是BlogController.java:

package com.demo.controller;

import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.demo.pojo.Blog;
import com.demo.service.BlogService;

@Controller
@RequestMapping(value = "/blog")
public class BlogController {
    private static final Logger LOG = LogManager.getLogger(BlogController.class);
    @Autowired
    private BlogService blogService;
    @RequestMapping(value="/pagehelper", method = RequestMethod.GET)
    public String blogPageHelper(HttpServletRequest request, @RequestParam(required=true,defaultValue="1") Integer page,
            @RequestParam(required=false,defaultValue="4") Integer pageSize, ModelMap model) {
        // 我这里起始的默认值是第1页, 每页的大小是4个, 读者可以根据需要改变
        LOG.info("page="+page+",pageSize="+pageSize); // 开始的打印结果: page=1,pageSize=4, 之后的page根据传入的值变化

        PageHelper.startPage(page, pageSize); //开始起始页
        List<Blog> blogList = blogService.selectBlogByList(); // 获取数据
        PageInfo<Blog> p = new PageInfo<Blog>(blogList); // 实例化PageInfo
        model.addAttribute("blogList", blogList);
        model.addAttribute("page", p); // 设置属性到前端页面
        return "blog/pagehelper";
    }
}

下面是前端的页面,即pagehelper.html:

前端页面我使用的是thymeleaf框架, 读者可以参考我的另一篇博客: thymeleaf 模板语言简介

<html xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8" />
<script type="text/javascript" th:src="@{/static/js/jquery-1.11.3.min.js}"></script>
<script type="text/javascript" th:src="@{/static/js/springDemo.js}"></script>
<link rel="stylesheet" th:href="@{/static/css/springDemo.css}" />
<title>SpringMVC + Mybatis + Spring</title>
</head>
<body>
    <div>
        <table class="example">
         <caption>Blog</caption>
            <thead>
                <tr>
                    <th>number</th>
                    <th>index</th>
                    <th>id</th>
                    <th>title</th>
                    <th>mainbody</th>
                    <th>creattime</th>
                </tr>
            </thead>
            <tbody th:remove="all-but-first">
                <tr th:each="blog,blogStat:${blogList}">
                    <td th:text="${blogStat.count}">1</td>
                    <td th:text="${blogStat.index}">0</td>
                    <td th:text="${blog.id}">title</td>
                    <td th:text="${blog.title}">title</td>
                    <td th:text="${blog.mainbody}">mainbody</td>
                    <td th:text="${blog.creattime}">creattime</td>
                </tr>
            </tbody>
            <tbody th:remove="all-but-first">  <!--我这里ui显示比较简单,就是为了方便显示-->
                <tr>
                    <td colspan="2"><p th:text="'Total:' + ${page.pages}">Total page</p></td>
                    <td><a th:href="@{/blog/pagehelper(page=1)}">first</a></td>
                    <td><a th:href="@{/blog/pagehelper(page=${page.nextPage})}">next</a></td>
                    <td><a th:href="@{/blog/pagehelper(page=${page.prePage})}">prex</a></td>
                    <td><a th:href="@{/blog/pagehelper(page=${page.lastPage})}">last</a></td>
                </tr>
            </tbody>
        </table>
    </div>
</body>
</html>

下面是运行后的界面显示效果:

在使用pagehelper时候, 发现出现下面问题:

14:18:54.095 [localhost-startStop-1] DEBUG org.hibernate.boot.registry.internal.BootstrapServiceRegistryImpl - Implicitly destroying Boot-strap registry on de-registration of all child ServiceRegistries
2018-04-22 14:18:54,103 [localhost-startStop-1] ERROR org.springframework.web.context.ContextLoader - Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sqlSessionFactory' defined in class path resource [conf/spring-mybatis.xml]: Initialization of bean failed; nested exception is org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'java.lang.Object[]' to required type 'org.apache.ibatis.plugin.Interceptor[]' for property 'plugins'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'com.github.pagehelper.PageHelper' to required type 'org.apache.ibatis.plugin.Interceptor' for property 'plugins[0]': no matching editors or conversion strategy found
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:591)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:502)
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:312)

解决办法就是: 把mybatis-config.xml中下面的更改过来

    <plugins>
        <!--注意这里要写成PageInterceptor, 5.0之前的版本都是写PageHelper, 5.0之后要换成PageInterceptor-->
        <plugin interceptor="com.github.pagehelper.PageInterceptor">
            <property name="helperDialect" value="mysql" />
            <property name="reasonable" value="true" />
        </plugin>
    </plugins>

还有一个小坑需要注意的是，在5.0以后的版本，使用了helperDialect代替了原来的dialect属性

下面把PageHelper 5.0与以前版本不一样的地方给贴出来。

1. 使用 QueryInterceptor 规范 处理分页逻辑 新的分页插件拦截器为 
   com.github.pagehelper.PageInterceptor 新的 PageHelper 是一个特殊的 Dialect
2. 实现类，以更友好的方式实现了以前的功能 新的分页插件仅有 dialect 一个参数，默认的 dialect 实现类为 PageHelper
3. PageHelper 仍然支持以前提供的参数，在最新的使用文档中已经全部更新 PageHelper 的 helperDialect 参数和以前的 dialect 功能一样，具体可以看文档的参数说明
4. 增加了基于纯 RowBounds 和 PageRowBounds 的分页实现，在com.github.pagehelper.dialect.rowbounds 包中，这是用于作为 dialect 参数示例的实现，后面会补充更详细的文档 去掉了不适合出现在分页插件中的 orderby功能，以后会提供单独的排序插件
5. 去掉了PageHelper 中不常用的方法新的文档，更新历来更新日志中提到的重要内容，提供英文版本文档 解决 bug 将 Db2RowDialect 改为Db2RowBoundsDialect 所有分页插件抛出的异常改为 PageException