springboot使用mybatis拦截进行SQL分页

新建一个类MyPageInterceptor.java（注意在springboot中要添加注解@Component）

package com.grand.p1upgrade.mapper.test;

import java.sql.Connection;
import java.util.Map;
import java.util.Properties;
import org.apache.ibatis.executor.parameter.ParameterHandler;
import org.apache.ibatis.executor.statement.StatementHandler;
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.springframework.stereotype.Component;

@Component
@Intercepts({@Signature(type=StatementHandler.class,method="prepare",args={Connection.class,Integer.class})})
public class MyPageInterceptor implements Interceptor {
    
    private int page;
    private int size;
    @SuppressWarnings("unused")
    private String dbType;
 
    @SuppressWarnings("unchecked")
    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        System.out.println("plugin is running...");
        StatementHandler statementHandler = (StatementHandler)invocation.getTarget();
        MetaObject metaObject = SystemMetaObject.forObject(statementHandler);
        while(metaObject.hasGetter("h")){
            Object object = metaObject.getValue("h");
            metaObject = SystemMetaObject.forObject(object);
        }
        while(metaObject.hasGetter("target")){
            Object object = metaObject.getValue("target");
            metaObject = SystemMetaObject.forObject(object);
        }
        MappedStatement mappedStatement = (MappedStatement)metaObject.getValue("delegate.mappedStatement");
        String mapId = mappedStatement.getId();
        if(mapId.matches(".+ByPager$")){
            ParameterHandler parameterHandler = (ParameterHandler)metaObject.getValue("delegate.parameterHandler");
            Map<String, Object> params = (Map<String, Object>)parameterHandler.getParameterObject();
            page = (int)params.get("page");
            size = (int)params.get("size");
            String sql = (String) metaObject.getValue("delegate.boundSql.sql");
            sql += " limit "+(page-1)*size +","+size;
            metaObject.setValue("delegate.boundSql.sql", sql);
        }
        return invocation.proceed();
    }
 
    @Override
    public Object plugin(Object target) {
        return Plugin.wrap(target, this);
    }
 
    @Override
    public void setProperties(Properties properties) {
        String limit = properties.getProperty("limit","10");
        this.page = Integer.parseInt(limit);
        this.dbType = properties.getProperty("dbType", "mysql");
    }
 
}

添加测试TestMapper.java

package com.grand.p1upgrade.mapper.test;

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

import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface TestMapper {

    public List<Map<String,Object>> findByPager(Map<String, Object> params);
    public long count();
}

TestMapper.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.grand.p1upgrade.mapper.test.TestMapper">

    <select id="findByPager" resultType="java.util.HashMap">
        select * from p1project.sys_user
    </select>
    <select id="count" resultType="long">
        select count(1) from p1project.sys_user
    </select>

   
</mapper>

在调用TestMapper.findByPager传递参数的时候将page和size传入即可