MyBatis分页插件：比PageHelper都要简单，使用很灵活，目前支持Oracle和MySQL

1、概述：

经过努力写了个分页插件，目前支持MySQL和Oracle。它的使用应该是目前为止最简单的，对于PageHelper据原作者描述使用了ThreadLocal等技术，避免多线程的不一致，PageHelper实现较为复杂，其次也有其定义的startPage,endPage这样的开关代码,造成代码侵入，而没有屏蔽PageHelper导致代码污染。

我的插件十分简单易用，代码污染性极小，也无需考虑多线程的问题，反正都是一个事务中处理的，其次使用方法支持四种，十分灵活。

2、插件代码，配置和简易的POJO

我们先看看插件的代码：

package com.learn.mybatis.plugin;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Iterator;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

import javax.transaction.NotSupportedException;

import org.apache.ibatis.executor.parameter.ParameterHandler;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
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.SystemMetaObject;
import org.apache.ibatis.scripting.defaults.DefaultParameterHandler;
import org.apache.ibatis.session.Configuration;
import org.apache.log4j.Logger;

import com.learn.mybatis.chapter1.main.MyBatisExample;

/**
*
* @author ykzhen2015
*/
@Intercepts({
@Signature(type = StatementHandler.class,
method = "prepare",
args = {Connection.class})})
public class PagingPlugin implements Interceptor {

/**
* 插件默认参数，可配置
*/
private Integer defaultPage; //默认页码
private Integer defaultPageSize;//默认每页条数
private Boolean defaultUseFlag; //默认是否启用插件
private Boolean defaultCheckFlag; //默认是否检测页码参数
private Boolean defaultCleanOrderBy; //默认是否清除最后一个order by 后的语句

private static final String DB_TYPE_MYSQL = "mysql";
private static final String DB_TYPE_ORACLE = "oracle";

/**
* 插件实现方法
*/
@Override
public Object intercept(Invocation invocation) throws Throwable {
StatementHandler stmtHandler = (StatementHandler) getUnProxyObject(invocation.getTarget());

MetaObject metaStatementHandler = SystemMetaObject.forObject(stmtHandler);
String sql = (String) metaStatementHandler.getValue("delegate.boundSql.sql");

MappedStatement mappedStatement =  (MappedStatement) metaStatementHandler.getValue("delegate.mappedStatement");
String dbType = this.getDataSourceType(mappedStatement);

//不是select语句.
if (!this.checkSelect(sql)) {
return invocation.proceed();
}
BoundSql boundSql = (BoundSql) metaStatementHandler.getValue("delegate.boundSql");
Object parameterObject = boundSql.getParameterObject();
PageParams pageParams = getPageParamsForParamObj(parameterObject);
if (pageParams == null) { //无法获取分页参数，不进行分页。
return invocation.proceed();
}

//获取配置中是否启用分页功能.
Boolean useFlag = pageParams.getUseFlag() == null? this.defaultUseFlag : pageParams.getUseFlag();
if (!useFlag) {  //不使用分页插件.
return invocation.proceed();
}
//获取相关配置的参数.
Integer pageNum = pageParams.getPage() == null? defaultPage : pageParams.getPage();
Integer pageSize = pageParams.getPageSize() == null? defaultPageSize : pageParams.getPageSize();
Boolean checkFlag = pageParams.getCheckFlag() == null? defaultCheckFlag : pageParams.getCheckFlag();
Boolean cleanOrderBy = pageParams.getCleanOrderBy() == null? defaultCleanOrderBy : pageParams.getCleanOrderBy();

int total = this.getTotal(invocation, metaStatementHandler, boundSql, cleanOrderBy, dbType);

pageParams.setTotal(total);
//计算总页数.
int totalPage = total % pageSize == 0 ? total / pageSize : total / pageSize + 1;
pageParams.setTotalPage(totalPage);
//检查当前页码的有效性.
this.checkPage(checkFlag, pageNum, totalPage);
//修改sql
return this.preparedSQL(invocation, metaStatementHandler, boundSql, pageNum, pageSize, dbType);
}

/***
* 分离出分页参数.
* @param parameterObject --执行参数
* @return 分页参数
* @throws Exception
*/
public PageParams getPageParamsForParamObj(Object parameterObject) throws Exception {
PageParams pageParams = null;
if (parameterObject == null) {
return null;
}
//处理map参数和@Param注解参数，都是MAP
if (parameterObject instanceof Map) {
@SuppressWarnings("unchecked")
Map<String, Object> paramMap = (Map<String, Object>) parameterObject;
Set<String> keySet = paramMap.keySet();
Iterator<String> iterator = keySet.iterator();
while(iterator.hasNext()) {
String key = iterator.next();
Object value = paramMap.get(key);
if (value instanceof PageParams) {
return (PageParams)value;
}
}
} else if (parameterObject instanceof PageParams) { //参数POJO继承了PageParams
return (PageParams) parameterObject;
} else { //从POJO尝试读取分页参数.
Field[] fields = parameterObject.getClass().getDeclaredFields();
//尝试从POJO中获得类型为PageParams的属性
for (Field field : fields) {
if (field.getType() == PageParams.class) {
PropertyDescriptor pd = new PropertyDescriptor (field.getName(), parameterObject.getClass());
Method method = pd.getReadMethod();
return (PageParams) method.invoke(parameterObject);
}
}
}
return pageParams;
}

/**
* 判断是否sql语句.
* @param sql
* @return
*/
private boolean checkSelect(String sql) {
String trimSql = sql.trim();
int idx = trimSql.toLowerCase().indexOf("select");
return idx == 0;
}

/**
* 检查当前页码的有效性.
* @param checkFlag
* @param pageNum
* @param pageTotal
* @throws Throwable
*/
private void checkPage(Boolean checkFlag, Integer pageNum, Integer pageTotal) throws Throwable  {
if (checkFlag) {
//检查页码page是否合法.
if (pageNum > pageTotal) {
throw new Exception("查询失败，查询页码【" + pageNum + "】大于总总页【" + pageTotal + "】！！");
}
}
}

/**
* 预编译改写后的SQL，并设置分页参数
* @param invocation
* @param metaStatementHandler
* @param boundSql
* @param pageNum
* @param pageSize
* @param dbType
* @throws IllegalAccessException
* @throws InvocationTargetException
*/
private Object preparedSQL(Invocation invocation, MetaObject metaStatementHandler, BoundSql boundSql, int pageNum, int pageSize, String dbType) throws Exception {
//获取当前需要执行的SQL
String sql = boundSql.getSql();
String newSql = this.getPageDataSQL(sql, dbType);
//修改当前需要执行的SQL
metaStatementHandler.setValue("delegate.boundSql.sql", newSql);
//执行编译，这里相当于StatementHandler执行了prepared()方法，这个时候，就剩下2个分页参数没有设置。
Object statementObj = invocation.proceed();
//设置两个分页参数。
this.preparePageDataParams((PreparedStatement)statementObj, pageNum, pageSize, dbType);
return statementObj;
}

/**
* 获取综述.
*
* @param ivt Invocation
* @param metaStatementHandler statementHandler
* @param boundSql sql
* @param cleanOrderBy 是否清除order by语句
* * @param dbType
* @return sql查询总数.
* @throws Throwable 异常.
*/
private int getTotal(Invocation ivt, MetaObject metaStatementHandler, BoundSql boundSql, Boolean cleanOrderBy, String dbType) throws Throwable {
//获取当前的mappedStatement
MappedStatement mappedStatement = (MappedStatement) metaStatementHandler.getValue("delegate.mappedStatement");
//配置对象
Configuration cfg = mappedStatement.getConfiguration();
//当前需要执行的SQL
String sql = (String) metaStatementHandler.getValue("delegate.boundSql.sql");
//去掉最后的order by语句
if (cleanOrderBy) {
sql = this.cleanOrderByForSql(sql);
}
String countSql = this.getTotalSQL(sql, dbType);
//获取拦截方法参数，根据插件签名，知道是Connection对象.
Connection connection = (Connection) ivt.getArgs()[0];
PreparedStatement ps = null;
int total = 0;
try {
//预编译统计总数SQL
ps = connection.prepareStatement(countSql);
//构建统计总数SQL
BoundSql countBoundSql = new BoundSql(cfg, countSql, boundSql.getParameterMappings(), boundSql.getParameterObject());
//构建MyBatis的ParameterHandler用来设置总数Sql的参数。
ParameterHandler handler = new DefaultParameterHandler(mappedStatement, boundSql.getParameterObject(), countBoundSql);
//设置总数SQL参数
handler.setParameters(ps);
//执行查询.
ResultSet rs = ps.executeQuery();
while (rs.next()) {
total = rs.getInt("total");
}
} finally {
//这里不能关闭Connection否则后续的SQL就没法继续了。
if (ps != null && ps.isClosed()) {
ps.close();
}
}
return total;
}

private String cleanOrderByForSql(String sql) {
StringBuilder sb = new StringBuilder(sql);
String newSql = sql.toLowerCase();
//如果没有order语句,直接返回
if (newSql.indexOf("order") == -1) {
return sql;
}
int idx = newSql.lastIndexOf("order");
return sb.substring(0, idx).toString();
}

/**
* 从代理对象中分离出真实对象.
*
* @param ivt --Invocation
* @return 非代理StatementHandler对象
*/
private Object getUnProxyObject(Object target) {
MetaObject metaStatementHandler = SystemMetaObject.forObject(target);
// 分离代理对象链(由于目标类可能被多个拦截器拦截，从而形成多次代理，通过循环可以分离出最原始的的目标类)
Object object = null;
while (metaStatementHandler.hasGetter("h")) {
object = metaStatementHandler.getValue("h");
}
if (object == null) {
return target;
}
return object;
}

/**
* 生成代理对象
* @param statementHandler 原始对象
* @return 代理对象
*/
@Override
public Object plugin(Object statementHandler) {
return Plugin.wrap(statementHandler, this);
}

/**
* 设置插件配置参数。
* @param props
*/
@Override
public void setProperties(Properties props) {
String strDefaultPage = props.getProperty("default.page", "1");
String strDefaultPageSize = props.getProperty("default.pageSize", "50");
String strDefaultUseFlag = props.getProperty("default.useFlag", "false");
String strDefaultCheckFlag = props.getProperty("default.checkFlag", "false");
String StringDefaultCleanOrderBy = props.getProperty("default.cleanOrderBy", "false");

this.defaultPage = Integer.parseInt(strDefaultPage);
this.defaultPageSize = Integer.parseInt(strDefaultPageSize);
this.defaultUseFlag = Boolean.parseBoolean(strDefaultUseFlag);
this.defaultCheckFlag = Boolean.parseBoolean(strDefaultCheckFlag);
this.defaultCleanOrderBy = Boolean.parseBoolean(StringDefaultCleanOrderBy);
}

/**
* TODO
* 计算总数的SQL,
* 这里需要根据数据库的类型改写SQL，目前支持MySQL和Oracle
* @param currSql —— 当前执行的SQL
* @return 改写后的SQL
* @throws NotSupportedException
*/
private String getTotalSQL(String currSql, String dbType) throws NotSupportedException {
if (DB_TYPE_MYSQL.equals(dbType)) {
return  "select count(*) as total from (" + currSql + ") $_paging";
} else if (DB_TYPE_ORACLE.equals(dbType)) {
return "select count(*) as total from (" + currSql +")";
} else {
throw new NotSupportedException("当前插件未支持此类型数据库");
}
}

/**
* TODO 需要使用其他数据库需要改写
* 分页获取参数的SQL
* 这里需要根据数据库的类型改写SQL，目前支持MySQL和Oracle
* @param currSql —— 当前执行的SQL
* @return 改写后的SQL
* @throws NotSupportedException
*/
private String getPageDataSQL(String currSql, String dbType) throws NotSupportedException {
if (DB_TYPE_MYSQL.equals(dbType)) {
return "select * from (" + currSql + ") $_paging_table limit ?, ?";
} else if (DB_TYPE_ORACLE.equals(dbType)) {
return " select * from (select cur_sql_result.*, rownum rn from (" + currSql + ") cur_sql_result  where rownum <= ?) where rn > ?";
} else {
throw new NotSupportedException("当前插件未支持此类型数据库");
}
}

/**
* TODO 需要使用其他数据库需要改写
* 使用PreparedStatement预编译两个分页参数，如果数据库的规则不一样，需要改写设置的参数规则。目前支持MySQL和Oracle
* @throws SQLException
* @throws NotSupportedException
*
*/
private void preparePageDataParams(PreparedStatement ps, int pageNum, int pageSize, String dbType) throws Exception {
//prepared()方法编译SQL，由于MyBatis上下文没有我们分页参数的信息，所以这里需要设置这两个参数.
//获取需要设置的参数个数，由于我们的参数是最后的两个，所以很容易得到其位置
int idx = ps.getParameterMetaData().getParameterCount();
if (DB_TYPE_MYSQL.equals(dbType)) {
//最后两个是我们的分页参数.
ps.setInt(idx -1, (pageNum - 1) * pageSize);//开始行
ps.setInt(idx, pageSize); //限制条数
} else if (DB_TYPE_ORACLE.equals(dbType)) {
ps.setInt(idx -1, pageNum * pageSize);//开始行
ps.setInt(idx, (pageNum - 1) * pageSize); //限制条数
} else {
throw new NotSupportedException("当前插件未支持此类型数据库");
}

}

/**
*
* TODO 需要使用其他数据库需要改写
* 目前支持MySQL和Oracle
* @param mappedStatement
* @return
* @throws Exception
*/
private String getDataSourceType(MappedStatement mappedStatement) throws Exception {
String dbConnectionStr = mappedStatement.getConfiguration().getEnvironment().getDataSource().getConnection().toString();
dbConnectionStr = dbConnectionStr.toLowerCase();
if (dbConnectionStr.contains(DB_TYPE_MYSQL)) {
return DB_TYPE_MYSQL;
} else if (dbConnectionStr.contains(DB_TYPE_ORACLE)) {
return DB_TYPE_ORACLE;
} else {
throw new NotSupportedException("当前插件未支持此类型数据库");
}
}

}

如果你是使用非Oracle或者MySQL的，你需要自己注解有TODO的方法，修改是也很简单。

有了这个插件，还要配置一下，MyBatis的配置文件如下：

<configuration>
......
<plugins>
<plugin interceptor="com.learn.mybatis.plugin.PagingPlugin">
<!-- 默认页码 -->
<property name="default.page" value="1" />
<!-- 默认每页条数-->
<property name="default.pageSize" value="20" />
<!-- 是否启动分页插件功能  -->
<property name="default.useFlag" value="true" />
<!-- 是否检查页码有效性，如果非有效，则抛出异常. -->
<property name="default.checkFlag" value="false" />
<!-- 针对哪些含有order by的SQL，是否去掉最后一个order by 以后的SQL语句，提高性能 -->
<property name="default.cleanOrderBy" value="false" />
</plugin>
</plugins>
......
</configuration>

上面我们可以看到一些默认值，可以根据我自己定义的一个POJO修改上面配置的默认值，这个POJO十分简单，它符合JavaBean的一切规范，如下：（其属性含义见其注解）

package com.learn.mybatis.plugin;

import java.util.List;

/**
*
* @author ykzhen2015
*/
public class PageParams {

private Integer page;//第几页
private Integer pageSize;//每页限制条数
private Boolean useFlag;//是否启动插件，如果不启动，则不作分页
private Boolean checkFlag;//是否检测页码的有效性，如果为true，而页码大于最大页数，则抛出异常
private Boolean cleanOrderBy;//是否清除最后order by 后面的语句
private Integer total; //总条数，插件会回填这个值
private Integer totalPage; //总页数，插件会回填这个值.

public Integer getPage() {
return page;
}

public void setPage(Integer page) {
this.page = page;
}

public Integer getPageSize() {
return pageSize;
}

public void setPageSize(Integer pageSize) {
this.pageSize = pageSize;
}

public Boolean getUseFlag() {
return useFlag;
}

public void setUseFlag(Boolean useFlag) {
this.useFlag = useFlag;
}

public Boolean getCheckFlag() {
return checkFlag;
}

public void setCheckFlag(Boolean checkFlag) {
this.checkFlag = checkFlag;
}

public Boolean getCleanOrderBy() {
return cleanOrderBy;
}

public void setCleanOrderBy(Boolean cleanOrderBy) {
this.cleanOrderBy = cleanOrderBy;
}

public Integer getTotal() {
return total;
}

public void setTotal(Integer total) {
this.total = total;
}

public Integer getTotalPage() {
return totalPage;
}

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

}

当以下属性被设置会有这样的效果：

page --插件默认设置default.page作废，采取这个值，整数型
pageSize --插件默认设置default.pageSize作废，采取这个值，整数型
useFlag --插件默认设置default.useFlag作废，采取这个值，布尔值
checkFlag --插件默认设置default.checkFlag作废，采取这个值，布尔值
cleanOrderBy -- 插件默认设置default.cleanOrderBy作废，采用这个值，布尔值

而：

total ——代表总条数，插件回自动帮我们回填，整数型

totalPage ——代表总页数，插件回自动帮我们回填，整数型

3、插件的使用：

这个插件使用起来十分简单，只要传递给MyBatis的SqlMap以下的方式都是允许的：

继承com.learn.mybatis.plugin.PageParams
使用map，但是map中的键值对应，有一个值是com.learn.mybatis.plugin.PageParams类型
使用@Param注解，只要里面有一个参数是com.learn.mybatis.plugin.PageParams类型

使用POJO，但是这个POJO中有一个属性为com.learn.mybatis.plugin.PageParams类型

以上4种形式都可以使用这个分页插件，是不是很多样性？？

让我们试用一下这个插件，看看这四种传递参数的方法。

现在我们定义一个map.xml如下：

<?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.learn.mybatis.chapter1.mapper.RoleMapper">
<select id="getRole" parameterType="long" resultType="com.learn.mybatis.chapter1.po.TRole">
select id, role_name as roleName, note from t_role where id=#{id}
</select>
<select id="selectAllRole" parameterType="com.learn.mybatis.plugin.TestParams" resultType="com.learn.mybatis.chapter1.po.TRole">
select id, role_name as roleName, note from t_role
<where>
<if test="roleName != null">
role_name like concat('%', #{roleName}, '%')
</if>

</where>
order by id desc
</select>

<select id="selectAllRole2" parameterType="com.learn.mybatis.plugin.TestParams2" resultType="com.learn.mybatis.chapter1.po.TRole">
select id, role_name as roleName, note from t_role
<where>
<if test="roleName != null">
role_name like concat('%', #{roleName}, '%')
</if>
</where>
order by id desc
</select>

<select id="selectRoleByMap" parameterType="map" resultType="com.learn.mybatis.chapter1.po.TRole">
select id, role_name as roleName, note from t_role
<where>
<if test="roleName != null">
role_name like concat('%', #{roleName}, '%')
</if>
</where>
order by id desc
</select>

<select id="selectRoleByMap2" resultType="com.learn.mybatis.chapter1.po.TRole">
select id, role_name as roleName, note from t_role
</select>

<select id="selectRoleByKey"  resultType="com.learn.mybatis.chapter1.po.TRole">
select id, role_name as roleName, note from t_role
<where>
<if test="roleName != null">
role_name like concat('%', #{roleName}, '%')
</if>
</where>
order by id desc
</select>

<select id="test$sql" resultType="com.learn.mybatis.chapter1.po.TRole">
select id, role_name as roleName, note from ${tableName}
<where>
<if test="roleName != null">
role_name like concat('%', #{roleName}, '%')
</if>
</where>
order by role_name desc
</select>
</mapper>

定义其接口：

package com.learn.mybatis.chapter1.mapper;

import java.util.List;
import java.util.Map;

import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.session.RowBounds;

import com.learn.mybatis.chapter1.po.TRole;
import com.learn.mybatis.plugin.PageParams;
import com.learn.mybatis.plugin.TestParams;
import com.learn.mybatis.plugin.TestParams2;

public interface RoleMapper {

//不含分页参数，就不会启用
public TRole getRole(Long id);

//继承方式
public List<TRole> selectAllRole(TestParams pageParams);

//参数为POJO，但是POJO内部包含一个类型为com.learn.mybatis.plugin.PageParams的属性
public List<TRole> selectAllRole2(TestParams2 testParams2);

//使用map,里面有一个com.learn.mybatis.plugin.PageParams类型的值
public List<TRole> selectRoleByMap(Map<String, Object> params);

//使用注解的形式传递分页参数。
public List<TRole> selectRoleByMap2(@Param("roleName") String roleName, @Param("page221232323")  PageParams pageParams);

}

好，看到注解，里面已经包含了上述4种传参的方法，这个插件都是支持的。先看到selectAllRole()方法

里面的参数TestParams定义（继承PageParams）：

package com.learn.mybatis.plugin;

public class TestParams extends PageParams {

String roleName;

public String getRoleName() {
return roleName;
}

public void setRoleName(String roleName) {
this.roleName = roleName;
}
}

再看到selectAllRole2()方法，里面的参数TestParams2定义（其属性有一个PageParams）:

package com.learn.mybatis.plugin;

public class TestParams2 {

private PageParams pageParams = null;
private String roleName;

public PageParams getPageParams() {
return pageParams;
}

public void setPageParams(PageParams pageParams) {
this.pageParams = pageParams;
}

public String getRoleName() {
return roleName;
}

public void setRoleName(String roleName) {
this.roleName = roleName;
}

}

好其他的都很简单了。

我们来测试这个接口，测试代码如下，注意看四种方式传递参数，代码的污染是很小的：

package com.learn.mybatis.chapter1.main;

import java.util.HashMap;
import java.util.Map;

import org.apache.ibatis.session.SqlSession;
import org.apache.log4j.Logger;

import com.learn.mybatis.chapter1.mapper.RoleMapper;
import com.learn.mybatis.chapter1.mb.util.MyBatisUtil;
import com.learn.mybatis.plugin.PageParams;
import com.learn.mybatis.plugin.TestParams;
import com.learn.mybatis.plugin.TestParams2;

public class MyBatisExample {

private static Logger logger = Logger.getLogger(MyBatisExample.class);
public static void main(String[] args) {
testGetRole();
testInherit();
testMap();
testAtParam();
testPojoProperty();

}

/**
* 继承PageParams的参数传递.
*/
public static void testGetRole() {
logger.info("#################测试没有分页参数的查询###########################");
SqlSession sqlSession = null;
try {
sqlSession = MyBatisUtil.getSqlSessionFactroy().openSession();
RoleMapper roleMapper = sqlSession.getMapper(RoleMapper.class);
roleMapper.getRole(1L);
} finally {
sqlSession.close();
}
}

/**
* 继承PageParams的参数传递.
*/
public static void testInherit() {
logger.info("#################测试分页参数以继承PageParams形式传递###########################");
SqlSession sqlSession = null;
try {
sqlSession = MyBatisUtil.getSqlSessionFactroy().openSession();
RoleMapper roleMapper = sqlSession.getMapper(RoleMapper.class);
TestParams params = new TestParams();
params.setUseFlag(true);
params.setCheckFlag(false);
params.setPage(2);
params.setPageSize(5);
params.setRoleName("test");
roleMapper.selectAllRole(params);
logger.info("总条数==>" + params.getTotal());
logger.info("总页数 ==>" + params.getTotalPage());
} finally {
sqlSession.close();
}
}

/**
* 使用map方式。（map的键随意取）
*/
public static void testMap() {
logger.info("#################测试分页参数以Map形式传递###########################");
SqlSession sqlSession = null;
try {
sqlSession = MyBatisUtil.getSqlSessionFactroy().openSession();
RoleMapper roleMapper = sqlSession.getMapper(RoleMapper.class);
Map<String, Object> paramMap = new HashMap<String, Object>();
PageParams pageParams = new PageParams();
pageParams.setUseFlag(true);
pageParams.setCheckFlag(false);
pageParams.setPage(2);
pageParams.setPageSize(5);
paramMap.put("roleName", "test");
paramMap.put("page_drsdsd2233", pageParams);
roleMapper.selectRoleByMap(paramMap);
logger.info("总条数==>" + pageParams.getTotal());
logger.info("总页数 ==>" + pageParams.getTotalPage());
} finally {
sqlSession.close();
}
}

/**
* 使用MyBatis  @Param注解 传递参数.
*/
public static void testAtParam() {
logger.info("#################测试分页参数以@Param形式传递###########################");
SqlSession sqlSession = null;
try {
sqlSession = MyBatisUtil.getSqlSessionFactroy().openSession();
RoleMapper roleMapper = sqlSession.getMapper(RoleMapper.class);
PageParams pageParams2 = new PageParams();
pageParams2.setUseFlag(true);
pageParams2.setCheckFlag(true);
pageParams2.setPage(2);
pageParams2.setPageSize(5);
pageParams2.setCleanOrderBy(true);
roleMapper.selectRoleByMap2("test", pageParams2);
logger.info("总条数==>" + pageParams2.getTotal());
logger.info("总页数 ==>" + pageParams2.getTotalPage());
} finally {
sqlSession.close();
}
}

/**
* 使用POJO传递，但是POJO内部有一个PageParams属性，和它的setter方法.
*/
public static void testPojoProperty() {
logger.info("#################测试分页参数作为参数属性传递###########################");
SqlSession sqlSession = null;
try {
sqlSession = MyBatisUtil.getSqlSessionFactroy().openSession();
RoleMapper roleMapper = sqlSession.getMapper(RoleMapper.class);
PageParams pageParams3 = new PageParams();
pageParams3.setUseFlag(true);
pageParams3.setCheckFlag(false);
pageParams3.setPage(3);
pageParams3.setPageSize(5);
pageParams3.setCleanOrderBy(true);
TestParams2 p2 = new TestParams2();
p2.setPageParams(pageParams3);
p2.setRoleName("test");
roleMapper.selectAllRole2(p2);
logger.info("总条数==>" + pageParams3.getTotal());
logger.info("总页数 ==>" + pageParams3.getTotalPage());
} finally {
sqlSession.close();
}
}
}

测试的结果如下（我这里使用mysql也可以使用oracle，我也有测试过的）：

INFO 2016-06-23 21:02:37,966 com.learn.mybatis.chapter1.main.MyBatisExample: #################测试没有分页参数的查询###########################
DEBUG 2016-06-23 21:02:38,169 org.apache.ibatis.logging.LogFactory: Logging initialized using 'class org.apache.ibatis.logging.slf4j.Slf4jImpl' adapter.
DEBUG 2016-06-23 21:02:38,186 org.apache.ibatis.datasource.pooled.PooledDataSource: PooledDataSource forcefully closed/removed all connections.
DEBUG 2016-06-23 21:02:38,186 org.apache.ibatis.datasource.pooled.PooledDataSource: PooledDataSource forcefully closed/removed all connections.
DEBUG 2016-06-23 21:02:38,186 org.apache.ibatis.datasource.pooled.PooledDataSource: PooledDataSource forcefully closed/removed all connections.
DEBUG 2016-06-23 21:02:38,186 org.apache.ibatis.datasource.pooled.PooledDataSource: PooledDataSource forcefully closed/removed all connections.
DEBUG 2016-06-23 21:02:38,267 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Opening JDBC Connection
DEBUG 2016-06-23 21:02:38,470 org.apache.ibatis.datasource.pooled.PooledDataSource: Created connection 103887628.
DEBUG 2016-06-23 21:02:38,470 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,485 org.apache.ibatis.datasource.pooled.PooledDataSource: Created connection 1752203484.
DEBUG 2016-06-23 21:02:38,486 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==>  Preparing: select id, role_name as roleName, note from t_role where id=?
DEBUG 2016-06-23 21:02:38,508 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==> Parameters: 1(Long)
DEBUG 2016-06-23 21:02:38,532 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: <==      Total: 0
DEBUG 2016-06-23 21:02:38,533 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,534 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,535 org.apache.ibatis.datasource.pooled.PooledDataSource: Returned connection 103887628 to pool.
INFO 2016-06-23 21:02:38,539 com.learn.mybatis.chapter1.main.MyBatisExample: #################测试分页参数以继承PageParams形式传递###########################
DEBUG 2016-06-23 21:02:38,565 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Opening JDBC Connection
DEBUG 2016-06-23 21:02:38,565 org.apache.ibatis.datasource.pooled.PooledDataSource: Checked out connection 103887628 from pool.
DEBUG 2016-06-23 21:02:38,565 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,575 org.apache.ibatis.datasource.pooled.PooledDataSource: Created connection 1682463303.
DEBUG 2016-06-23 21:02:38,576 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==>  Preparing: select count(*) as total from (select id, role_name as roleName, note from t_role WHERE role_name like concat('%', ?, '%') order by id desc) $_paging
DEBUG 2016-06-23 21:02:38,576 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==> Parameters: test(String)
DEBUG 2016-06-23 21:02:38,577 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: <==      Total: 1
DEBUG 2016-06-23 21:02:38,577 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==>  Preparing: select * from (select id, role_name as roleName, note from t_role WHERE role_name like concat('%', ?, '%') order by id desc) $_paging_table limit ?, ?
DEBUG 2016-06-23 21:02:38,579 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==> Parameters: 5(Integer), 5(Integer), test(String)
DEBUG 2016-06-23 21:02:38,583 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: <==      Total: 5
INFO 2016-06-23 21:02:38,584 com.learn.mybatis.chapter1.main.MyBatisExample: 总条数==>10
INFO 2016-06-23 21:02:38,584 com.learn.mybatis.chapter1.main.MyBatisExample: 总页数 ==>2
DEBUG 2016-06-23 21:02:38,584 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,585 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,585 org.apache.ibatis.datasource.pooled.PooledDataSource: Returned connection 103887628 to pool.
INFO 2016-06-23 21:02:38,585 com.learn.mybatis.chapter1.main.MyBatisExample: #################测试分页参数以Map形式传递###########################
DEBUG 2016-06-23 21:02:38,588 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Opening JDBC Connection
DEBUG 2016-06-23 21:02:38,588 org.apache.ibatis.datasource.pooled.PooledDataSource: Checked out connection 103887628 from pool.
DEBUG 2016-06-23 21:02:38,588 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,601 org.apache.ibatis.datasource.pooled.PooledDataSource: Created connection 156545103.
DEBUG 2016-06-23 21:02:38,601 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==>  Preparing: select count(*) as total from (select id, role_name as roleName, note from t_role WHERE role_name like concat('%', ?, '%') order by id desc) $_paging
DEBUG 2016-06-23 21:02:38,602 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==> Parameters: test(String)
DEBUG 2016-06-23 21:02:38,604 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: <==      Total: 1
DEBUG 2016-06-23 21:02:38,604 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==>  Preparing: select * from (select id, role_name as roleName, note from t_role WHERE role_name like concat('%', ?, '%') order by id desc) $_paging_table limit ?, ?
DEBUG 2016-06-23 21:02:38,605 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==> Parameters: 5(Integer), 5(Integer), test(String)
DEBUG 2016-06-23 21:02:38,608 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: <==      Total: 5
INFO 2016-06-23 21:02:38,609 com.learn.mybatis.chapter1.main.MyBatisExample: 总条数==>10
INFO 2016-06-23 21:02:38,609 com.learn.mybatis.chapter1.main.MyBatisExample: 总页数 ==>2
DEBUG 2016-06-23 21:02:38,609 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,610 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,610 org.apache.ibatis.datasource.pooled.PooledDataSource: Returned connection 103887628 to pool.
INFO 2016-06-23 21:02:38,610 com.learn.mybatis.chapter1.main.MyBatisExample: #################测试分页参数以@Param形式传递###########################
DEBUG 2016-06-23 21:02:38,612 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Opening JDBC Connection
DEBUG 2016-06-23 21:02:38,613 org.apache.ibatis.datasource.pooled.PooledDataSource: Checked out connection 103887628 from pool.
DEBUG 2016-06-23 21:02:38,613 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,627 org.apache.ibatis.datasource.pooled.PooledDataSource: Created connection 668210649.
DEBUG 2016-06-23 21:02:38,627 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==>  Preparing: select count(*) as total from (select id, role_name as roleName, note from t_role) $_paging
DEBUG 2016-06-23 21:02:38,628 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==> Parameters:
DEBUG 2016-06-23 21:02:38,630 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: <==      Total: 1
DEBUG 2016-06-23 21:02:38,630 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==>  Preparing: select * from (select id, role_name as roleName, note from t_role) $_paging_table limit ?, ?
DEBUG 2016-06-23 21:02:38,631 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==> Parameters: 5(Integer), 5(Integer)
DEBUG 2016-06-23 21:02:38,633 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: <==      Total: 5
INFO 2016-06-23 21:02:38,634 com.learn.mybatis.chapter1.main.MyBatisExample: 总条数==>10
INFO 2016-06-23 21:02:38,634 com.learn.mybatis.chapter1.main.MyBatisExample: 总页数 ==>2
DEBUG 2016-06-23 21:02:38,634 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,635 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,635 org.apache.ibatis.datasource.pooled.PooledDataSource: Returned connection 103887628 to pool.
INFO 2016-06-23 21:02:38,635 com.learn.mybatis.chapter1.main.MyBatisExample: #################测试分页参数作为参数属性传递###########################
DEBUG 2016-06-23 21:02:38,636 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Opening JDBC Connection
DEBUG 2016-06-23 21:02:38,636 org.apache.ibatis.datasource.pooled.PooledDataSource: Checked out connection 103887628 from pool.
DEBUG 2016-06-23 21:02:38,636 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,643 org.apache.ibatis.datasource.pooled.PooledDataSource: Created connection 1361289747.
DEBUG 2016-06-23 21:02:38,644 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==>  Preparing: select count(*) as total from (select id, role_name as roleName, note from t_role WHERE role_name like concat('%', ?, '%') ) $_paging
DEBUG 2016-06-23 21:02:38,644 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==> Parameters: test(String)
DEBUG 2016-06-23 21:02:38,645 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: <==      Total: 1
DEBUG 2016-06-23 21:02:38,645 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==>  Preparing: select * from (select id, role_name as roleName, note from t_role WHERE role_name like concat('%', ?, '%') order by id desc) $_paging_table limit ?, ?
DEBUG 2016-06-23 21:02:38,646 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==> Parameters: 10(Integer), 5(Integer), test(String)
DEBUG 2016-06-23 21:02:38,648 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: <==      Total: 0
INFO 2016-06-23 21:02:38,648 com.learn.mybatis.chapter1.main.MyBatisExample: 总条数==>10
INFO 2016-06-23 21:02:38,648 com.learn.mybatis.chapter1.main.MyBatisExample: 总页数 ==>2
DEBUG 2016-06-23 21:02:38,648 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,649 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@631330c]
DEBUG 2016-06-23 21:02:38,649 org.apache.ibatis.datasource.pooled.PooledDataSource: Returned connection 103887628 to pool.

此时为了测试验证页码的和去掉order by语句的效果，我们再把testPojoProperty()方法修改一下：

/**
* 使用POJO传递，但是POJO内部有一个PageParams属性，和它的setter方法.
*/
public static void testPojoProperty() {
logger.info("#################测试分页参数作为参数属性传递###########################");
SqlSession sqlSession = null;
try {
sqlSession = MyBatisUtil.getSqlSessionFactroy().openSession();
RoleMapper roleMapper = sqlSession.getMapper(RoleMapper.class);
PageParams pageParams3 = new PageParams();
pageParams3.setUseFlag(true);
pageParams3.setCheckFlag(true);
pageParams3.setPage(6);
pageParams3.setPageSize(5);
pageParams3.setCleanOrderBy(false);
TestParams2 p2 = new TestParams2();
p2.setPageParams(pageParams3);
p2.setRoleName("test");
roleMapper.selectAllRole2(p2);
logger.info("总条数==>" + pageParams3.getTotal());
logger.info("总页数 ==>" + pageParams3.getTotalPage());
} finally {
sqlSession.close();
}
}

再运行一下，得到日志：

 INFO 2016-06-23 21:09:09,643 com.learn.mybatis.chapter1.main.MyBatisExample: #################测试分页参数作为参数属性传递###########################
DEBUG 2016-06-23 21:09:09,839 org.apache.ibatis.logging.LogFactory: Logging initialized using 'class org.apache.ibatis.logging.slf4j.Slf4jImpl' adapter.
DEBUG 2016-06-23 21:09:09,856 org.apache.ibatis.datasource.pooled.PooledDataSource: PooledDataSource forcefully closed/removed all connections.
DEBUG 2016-06-23 21:09:09,856 org.apache.ibatis.datasource.pooled.PooledDataSource: PooledDataSource forcefully closed/removed all connections.
DEBUG 2016-06-23 21:09:09,856 org.apache.ibatis.datasource.pooled.PooledDataSource: PooledDataSource forcefully closed/removed all connections.
DEBUG 2016-06-23 21:09:09,857 org.apache.ibatis.datasource.pooled.PooledDataSource: PooledDataSource forcefully closed/removed all connections.
DEBUG 2016-06-23 21:09:09,957 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Opening JDBC Connection
DEBUG 2016-06-23 21:09:10,166 org.apache.ibatis.datasource.pooled.PooledDataSource: Created connection 142555199.
DEBUG 2016-06-23 21:09:10,166 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@87f383f]
DEBUG 2016-06-23 21:09:10,181 org.apache.ibatis.datasource.pooled.PooledDataSource: Created connection 192794887.
DEBUG 2016-06-23 21:09:10,182 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==>  Preparing: select count(*) as total from (select id, role_name as roleName, note from t_role WHERE role_name like concat('%', ?, '%') order by id desc) $_paging
DEBUG 2016-06-23 21:09:10,218 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: ==> Parameters: test(String)
DEBUG 2016-06-23 21:09:10,243 org.apache.ibatis.logging.jdbc.BaseJdbcLogger: <==      Total: 1
DEBUG 2016-06-23 21:09:10,245 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@87f383f]
DEBUG 2016-06-23 21:09:10,245 org.apache.ibatis.transaction.jdbc.JdbcTransaction: Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@87f383f]
DEBUG 2016-06-23 21:09:10,246 org.apache.ibatis.datasource.pooled.PooledDataSource: Returned connection 142555199 to pool.
Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException:
### Error querying database.  Cause: java.lang.reflect.UndeclaredThrowableException
### The error may exist in com\learn\mybatis\chapter1\sqlmap\role.xml
### The error may involve com.learn.mybatis.chapter1.mapper.RoleMapper.selectAllRole2-Inline
### The error occurred while setting parameters
### Cause: java.lang.reflect.UndeclaredThrowableException
    at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:26)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:111)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:102)
    at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:119)
    at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:63)
    at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:52)
    at com.sun.proxy.$Proxy4.selectAllRole2(Unknown Source)
    at com.learn.mybatis.chapter1.main.MyBatisExample.testPojoProperty(MyBatisExample.java:131)
    at com.learn.mybatis.chapter1.main.MyBatisExample.main(MyBatisExample.java:23)
Caused by: java.lang.reflect.UndeclaredThrowableException
    at com.sun.proxy.$Proxy5.prepare(Unknown Source)
    at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:73)
    at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:59)
    at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:267)
    at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:137)
    at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:96)
    at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:77)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:108)
    ... 7 more
Caused by: java.lang.Exception: 查询失败，查询页码【6】大于总总页【2】！！
    at com.learn.mybatis.plugin.PagingPlugin.checkPage(PagingPlugin.java:168)
    at com.learn.mybatis.plugin.PagingPlugin.intercept(PagingPlugin.java:99)
    at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:60)
    ... 15 more

说明页码超过了最大的页数，注意这里的因为有了这句：pageParams3.setCleanOrderBy(false);所以从日志可以看出，和上次不太一样，插件没有帮我们去掉了影响性能的order by语句。这些都是可以通过参数由你来控制的。当然使用默认的参数也是可以的。