mybatis在mysql中的分页扩展

applicationContext.xml

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

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>
		<!-- 设置成 true就可以启动缓存，一般的修改要1分钟才能生效（因为设置的flushInterval="60000" ）
			 如果是在一个xxxxMapper.xml里面修改的数据库的数据,就直接清空本mapper的缓存 -->
		<setting name="cacheEnabled" value="false"/>
		<setting name="useGeneratedKeys" value="false"/>
	</settings>
	<plugins>
		<plugin interceptor="com.system.util.DiclectStatementHandlerInterceptor" />
		<plugin interceptor="com.system.util.DiclectResultSetHandlerInterceptor" />
	</plugins>
</configuration>

DiclectResultSetHandlerInterceptor.java

package com.system.util;

import java.sql.Statement;
import java.util.Properties;

import org.apache.ibatis.executor.resultset.FastResultSetHandler;
import org.apache.ibatis.executor.resultset.NestedResultSetHandler;
import org.apache.ibatis.executor.resultset.ResultSetHandler;
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.session.RowBounds;

@Intercepts({ @Signature(type = ResultSetHandler.class, method = "handleResultSets", args = { Statement.class }) })
public class DiclectResultSetHandlerInterceptor implements Interceptor {

	public Object intercept(Invocation invocation) throws Throwable {
		FastResultSetHandler resultSet = (FastResultSetHandler) invocation.getTarget();
		if(!(resultSet instanceof NestedResultSetHandler)) {
			RowBounds rowBounds = (RowBounds) ReflectUtil.getClassField(resultSet, "rowBounds");
			if (rowBounds.getLimit() > 0 && rowBounds.getLimit() < RowBounds.NO_ROW_LIMIT) {
				ReflectUtil.setClassField(resultSet, "rowBounds", new RowBounds());
			}
		}
		return invocation.proceed();
	}

	public Object plugin(Object target) {
		return Plugin.wrap(target, this);
	}

	public void setProperties(Properties properties) {}
}

DiclectStatementHandlerInterceptor.java

package com.system.util;

import java.sql.Connection;
import java.util.Properties;

import org.apache.ibatis.executor.statement.PreparedStatementHandler;
import org.apache.ibatis.executor.statement.RoutingStatementHandler;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
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.session.RowBounds;

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

	public Object intercept(Invocation invocation) throws Throwable {
		RoutingStatementHandler statement = (RoutingStatementHandler) invocation.getTarget();
		StatementHandler handler = (StatementHandler) ReflectUtil.getClassField(statement, "delegate");
		if (handler instanceof PreparedStatementHandler){
			RowBounds rowBounds = (RowBounds) ReflectUtil.getSuperClassField(handler, "rowBounds");
			if (rowBounds.getLimit() > 0 && rowBounds.getLimit() < RowBounds.NO_ROW_LIMIT) {
				BoundSql boundSql = statement.getBoundSql();
				String sql = boundSql.getSql();
				sql = getLimitString(sql, rowBounds.getOffset(), rowBounds.getLimit());
				ReflectUtil.setClassField(boundSql, "sql", sql);
			}
		}
		return invocation.proceed();
	}

	public Object plugin(Object target) {
		return Plugin.wrap(target, this);
	}

	public void setProperties(Properties properties) {
	}

	public String getLimitString(String sql, int offset, int limit) {
		limit = offset+limit;
		sql = sql.trim();
		boolean isForUpdate = false;
		if ( sql.toLowerCase().endsWith(" for update") ) {
			sql = sql.substring( 0, sql.length()-11 );
			isForUpdate = true;
		}
		StringBuffer pagingSelect = new StringBuffer( sql.length()+100 );
		pagingSelect.append(sql);

		pagingSelect.append(" limit "+offset+","+limit);
		if ( isForUpdate ) {
			pagingSelect.append( " for update" );
		}

		return pagingSelect.toString();
	}
}