MyBatis3-实现MyBatis分页

此文章中的例子是沿用上一篇文章http://www.cnblogs.com/EasonJim/p/7055499.html的Spring MVC集成的例子改装的。

MyBatis分页有以下方式实现：

一、内存分页，使用RowBounds类，但这种方式不推荐，基本不用，所以此方式集成省略。

二、自定义实现，代码量比较少，简单，比较灵活。以下为具体的集成步骤：

1、在User.xml中加入select节点，并组装分页SQL

    <select id="getUserArticlesByLimit" parameterType="int" resultMap="resultUserArticleList">
        select user.id,user.userName,user.userAddress,article.id as aid,article.title,article.content from user,article where user.id=article.userid and user.id=#{arg0} limit #{arg1},#{arg2}
    </select>

注意：上面的写法中select节点的parameterType属性为int类型，而此时是由于当前业务的SQL语句就是全部都是int型的，当对于多类型时，这种属性就不能这么设置了。具体的在多参数中会进行讲解。

2、在IUserOperation.java中加入Mapping对应的方法

public List<Article> getUserArticlesByLimit(int id,int start,int limit);

3、修改UserController.java中获取数据的方法，改成分页方法，并传入指定参数

package com.jsoft.testmybatis.controller;

import java.util.List;

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

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

import com.jsoft.testmybatis.inter.IUserOperation;
import com.jsoft.testmybatis.models.Article;

@Controller
@RequestMapping("/article")
public class UserController {
    @Autowired
    IUserOperation userMapper;

    @RequestMapping("/list")
    public ModelAndView listall(HttpServletRequest request,HttpServletResponse response){
        List<Article> articles=userMapper.getUserArticlesByLimit(1,0,2);
        ModelAndView mav=new ModelAndView("/article/list");
        mav.addObject("articles",articles);
        return mav;
    }
}

意思是获取用户1的数据，从第0行开始的2条数据。

4、运行测试

mvn tomcat7:run

三、通过自定义插件的形式实现分页，也是最好的，也叫做分页拦截器。实现步骤如下：

插件支持MySQL和Oracle两种数据库，通过方法名关键字ListPage去匹配，有才进行分页处理，并且不用在Mapping中写分页代码。

1、在User.xml中添加查询语句

    <!-- 插件式分页查询测试 -->
    <select id="selectArticleListPage" resultMap="resultUserArticleList">
        select user.id,user.userName,user.userAddress,article.id as aid,article.title,article.content from user,article where user.id=article.userid and user.id=#{userid}
    </select>

2、在IUserOperation.java中添加接口

    public List<Article> selectArticleListPage(
            @Param("page")
            PageInfo page,
            @Param("userid")
            int userid);

3、以下是插件实现的三个类

PageInfo.java:

package com.jsoft.testmybatis.util;

import java.io.Serializable;

public class PageInfo implements Serializable {

    private static final long serialVersionUID = 587754556498974978L;

    // pagesize ，每一页显示多少
    private int showCount = 3;
    // 总页数
    private int totalPage;
    // 总记录数
    private int totalResult;
    // 当前页数
    private int currentPage;
    // 当前显示到的ID, 在mysql limit 中就是第一个参数.
    private int currentResult;
    private String sortField;
    private String order;

    public int getShowCount() {
        return showCount;
    }

    public void setShowCount(int showCount) {
        this.showCount = showCount;
    }

    public int getTotalPage() {
        return totalPage;
    }

    public void setTotalPage(int totalPage) {
        this.totalPage = totalPage;
    }

    public int getTotalResult() {
        return totalResult;
    }

    public void setTotalResult(int totalResult) {
        this.totalResult = totalResult;
    }

    public int getCurrentPage() {
        return currentPage;
    }

    public void setCurrentPage(int currentPage) {
        this.currentPage = currentPage;
    }

    public int getCurrentResult() {
        return currentResult;
    }

    public void setCurrentResult(int currentResult) {
        this.currentResult = currentResult;
    }

    public String getSortField() {
        return sortField;
    }

    public void setSortField(String sortField) {
        this.sortField = sortField;
    }

    public String getOrder() {
        return order;
    }

    public void setOrder(String order) {
        this.order = order;
    }

}

ReflectHelper.java：

package com.jsoft.testmybatis.util;

import java.lang.reflect.Field;

public class ReflectHelper {
    public static Field getFieldByFieldName(Object obj, String fieldName) {
        for (Class<?> superClass = obj.getClass(); superClass != Object.class; superClass = superClass.getSuperclass()) {
            try {
                return superClass.getDeclaredField(fieldName);
            } catch (NoSuchFieldException e) {
            }
        }
        return null;
    }

    /**
     * Obj fieldName的获取属性值.
     *
     * @param obj
     * @param fieldName
     * @return
     * @throws SecurityException
     * @throws NoSuchFieldException
     * @throws IllegalArgumentException
     * @throws IllegalAccessException
     */
    public static Object getValueByFieldName(Object obj, String fieldName) throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException {
        Field field = getFieldByFieldName(obj, fieldName);
        Object value = null;
        if (field != null) {
            if (field.isAccessible()) {
                value = field.get(obj);
            } else {
                field.setAccessible(true);
                value = field.get(obj);
                field.setAccessible(false);
            }
        }
        return value;
    }

    /**
     * obj fieldName设置的属性值.
     *
     * @param obj
     * @param fieldName
     * @param value
     * @throws SecurityException
     * @throws NoSuchFieldException
     * @throws IllegalArgumentException
     * @throws IllegalAccessException
     */
    public static void setValueByFieldName(Object obj, String fieldName, Object value) throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException {
        Field field = obj.getClass().getDeclaredField(fieldName);
        if (field.isAccessible()) {
            field.set(obj, value);
        } else {
            field.setAccessible(true);
            field.set(obj, value);
            field.setAccessible(false);
        }
    }

}

PagePlugin.java：

package com.jsoft.testmybatis.util;

import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;
import java.util.Map;
import java.util.Properties;

import javax.xml.bind.PropertyException;

import org.apache.ibatis.scripting.xmltags.ForEachSqlNode;
import org.apache.ibatis.executor.ErrorContext;
import org.apache.ibatis.executor.ExecutorException;
import org.apache.ibatis.executor.statement.BaseStatementHandler;
import org.apache.ibatis.executor.statement.RoutingStatementHandler;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.ParameterMapping;
import org.apache.ibatis.mapping.ParameterMode;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.property.PropertyTokenizer;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.type.TypeHandler;
import org.apache.ibatis.type.TypeHandlerRegistry;

@Intercepts({ @Signature(type = StatementHandler.class, method = "prepare", args = { Connection.class, Integer.class }) })
public class PagePlugin implements Interceptor {

    private static String dialect = "";
    private static String pageSqlId = "";

    @SuppressWarnings("unchecked")
    public Object intercept(Invocation ivk) throws Throwable {

        if (ivk.getTarget() instanceof RoutingStatementHandler) {
            RoutingStatementHandler statementHandler = (RoutingStatementHandler) ivk.getTarget();
            BaseStatementHandler delegate = (BaseStatementHandler) ReflectHelper.getValueByFieldName(statementHandler, "delegate");
            MappedStatement mappedStatement = (MappedStatement) ReflectHelper.getValueByFieldName(delegate, "mappedStatement");

            if (mappedStatement.getId().matches(pageSqlId)) {
                BoundSql boundSql = delegate.getBoundSql();
                Object parameterObject = boundSql.getParameterObject();
                if (parameterObject == null) {
                    throw new NullPointerException("parameterObject error");
                } else {
                    Connection connection = (Connection) ivk.getArgs()[0];
                    String sql = boundSql.getSql();
                    String countSql = "select count(0) from (" + sql + ") myCount";
                    System.out.println("总数sql 语句:" + countSql);
                    PreparedStatement countStmt = connection.prepareStatement(countSql);
                    BoundSql countBS = new BoundSql(mappedStatement.getConfiguration(), countSql, boundSql.getParameterMappings(), parameterObject);
                    setParameters(countStmt, mappedStatement, countBS, parameterObject);
                    ResultSet rs = countStmt.executeQuery();
                    int count = 0;
                    if (rs.next()) {
                        count = rs.getInt(1);
                    }
                    rs.close();
                    countStmt.close();

                    PageInfo page = null;
                    if (parameterObject instanceof PageInfo) {
                        page = (PageInfo) parameterObject;
                        page.setTotalResult(count);
                    } else if (parameterObject instanceof Map) {
                        Map<String, Object> map = (Map<String, Object>) parameterObject;
                        page = (PageInfo) map.get("page");
                        if (page == null)
                            page = new PageInfo();
                        page.setTotalResult(count);
                    } else {
                        Field pageField = ReflectHelper.getFieldByFieldName(parameterObject, "page");
                        if (pageField != null) {
                            page = (PageInfo) ReflectHelper.getValueByFieldName(parameterObject, "page");
                            if (page == null)
                                page = new PageInfo();
                            page.setTotalResult(count);
                            ReflectHelper.setValueByFieldName(parameterObject, "page", page);
                        } else {
                            throw new NoSuchFieldException(parameterObject.getClass().getName());
                        }
                    }
                    String pageSql = generatePageSql(sql, page);
                    System.out.println("page sql:" + pageSql);
                    ReflectHelper.setValueByFieldName(boundSql, "sql", pageSql);
                }
            }
        }
        return ivk.proceed();
    }

    private void setParameters(PreparedStatement ps, MappedStatement mappedStatement, BoundSql boundSql, Object parameterObject) throws SQLException {
        ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());
        List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
        if (parameterMappings != null) {
            Configuration configuration = mappedStatement.getConfiguration();
            TypeHandlerRegistry typeHandlerRegistry = configuration.getTypeHandlerRegistry();
            MetaObject metaObject = parameterObject == null ? null : configuration.newMetaObject(parameterObject);
            for (int i = 0; i < parameterMappings.size(); i++) {
                ParameterMapping parameterMapping = parameterMappings.get(i);
                if (parameterMapping.getMode() != ParameterMode.OUT) {
                    Object value;
                    String propertyName = parameterMapping.getProperty();
                    PropertyTokenizer prop = new PropertyTokenizer(propertyName);
                    if (parameterObject == null) {
                        value = null;
                    } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
                        value = parameterObject;
                    } else if (boundSql.hasAdditionalParameter(propertyName)) {
                        value = boundSql.getAdditionalParameter(propertyName);
                    } else if (propertyName.startsWith(ForEachSqlNode.ITEM_PREFIX) && boundSql.hasAdditionalParameter(prop.getName())) {
                        value = boundSql.getAdditionalParameter(prop.getName());
                        if (value != null) {
                            value = configuration.newMetaObject(value).getValue(propertyName.substring(prop.getName().length()));
                        }
                    } else {
                        value = metaObject == null ? null : metaObject.getValue(propertyName);
                    }
                    TypeHandler typeHandler = parameterMapping.getTypeHandler();
                    if (typeHandler == null) {
                        throw new ExecutorException("There was no TypeHandler found for parameter " + propertyName + " of statement " + mappedStatement.getId());
                    }
                    typeHandler.setParameter(ps, i + 1, value, parameterMapping.getJdbcType());
                }
            }
        }
    }

    private String generatePageSql(String sql, PageInfo page) {
        if (page != null && (dialect != null || !dialect.equals(""))) {
            StringBuffer pageSql = new StringBuffer();
            if ("mysql".equals(dialect)) {
                pageSql.append(sql);
                pageSql.append(" limit " + page.getCurrentResult() + "," + page.getShowCount());
            } else if ("oracle".equals(dialect)) {
                pageSql.append("select * from (select tmp_tb.*,ROWNUM row_id from (");
                pageSql.append(sql);
                pageSql.append(")  tmp_tb where ROWNUM<=");
                pageSql.append(page.getCurrentResult() + page.getShowCount());
                pageSql.append(") where row_id>");
                pageSql.append(page.getCurrentResult());
            }
            return pageSql.toString();
        } else {
            return sql;
        }
    }

    public Object plugin(Object arg0) {
        // TODO Auto-generated method stub
        return Plugin.wrap(arg0, this);
    }

    public void setProperties(Properties p) {
        dialect = p.getProperty("dialect");
        if (dialect == null || dialect.equals("")) {
            try {
                throw new PropertyException("dialect property is not found!");
            } catch (PropertyException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        pageSqlId = p.getProperty("pageSqlId");
        if (dialect == null || dialect.equals("")) {
            try {
                throw new PropertyException("pageSqlId property is not found!");
            } catch (PropertyException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }

}

4、在Configuration.xml中配置插件

<?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>
    <typeAliases>
        <typeAlias alias="PageInfo" type="com.jsoft.testmybatis.util.PageInfo" />
    </typeAliases>
    <plugins>
        <plugin interceptor="com.jsoft.testmybatis.util.PagePlugin">
            <property name="dialect" value="mysql" />
            <property name="pageSqlId" value=".*ListPage.*" />
        </plugin>
    </plugins>

</configuration>

注意：这个插件定义了一个规则，也就是在mapper中SQL语句的id必须包含ListPage才能被拦截。否则将不会分页处理。

5、在UserController.java中添加测试的Controller

    @RequestMapping("/pagelist")
    public ModelAndView pageList(HttpServletRequest request, HttpServletResponse response) {
        int currentPage = request.getParameter("page") == null ? 1 : Integer.parseInt(request.getParameter("page"));
        int pageSize = 3;
        if (currentPage <= 0) {
            currentPage = 1;
        }
        int currentResult = (currentPage - 1) * pageSize;

        System.out.println(request.getRequestURI());
        System.out.println(request.getQueryString());

        PageInfo page = new PageInfo();
        page.setShowCount(pageSize);
        page.setCurrentResult(currentResult);
        List<Article> articles = userMapper.selectArticleListPage(page, 1);

        System.out.println(page);

        int totalCount = page.getTotalResult();

        int lastPage = 0;
        if (totalCount % pageSize == 0) {
            lastPage = totalCount % pageSize;
        } else {
            lastPage = 1 + totalCount / pageSize;
        }

        if (currentPage >= lastPage) {
            currentPage = lastPage;
        }

        String pageStr = "";

        pageStr = String.format("<a href=\"%s\">上一页</a>    <a href=\"%s\">下一页</a>", request.getRequestURI() + "?page=" + (currentPage - 1), request.getRequestURI() + "?page=" + (currentPage + 1));

        // 制定视图，也就是list.jsp
        ModelAndView mav = new ModelAndView("/article/pagelist");
        mav.addObject("articles", articles);
        mav.addObject("pageStr", pageStr);
        return mav;
    }

6、页面文件pagelist.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" isELIgnored="false"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
    <c:forEach items="${articles}" var="item">
        ${item.id }--${item.title }--${item.content }<br />
    </c:forEach>
    <div style="padding:20px;">${pageStr}</div>
</body>
</html>

7、测试结果：

测试工程：https://github.com/easonjim/5_java_example/tree/master/mybatis/test7