MyBatis3缓存与分页

1. MyBatis3缓存

Mybatis默认情况下，MyBatis启用一级缓存，即同一个SqlSession接口对象调用了相同的select语句，则直接会从缓存中返回结果，而不是再查询一次数据库；
开发者可以自己配置二级缓存，二级缓存是全局的；
默认情况下，select使用缓存的，insert update delete是不使用缓存的；

<cache size="1024" flushInterval="60000" eviction="LRU" readOnly="false"/>
1) size:表示缓存cache中能容纳的最大元素数。默认是1024；
2) flushInterval:定义缓存刷新周期，以毫秒计；
3) eviction:定义缓存的移除机制；默认是LRU(leastrecentlyuserd，最近最少使用),还有FIFO(firstinfirstout，先进先出)    
4) readOnly:默认值是false，假如是true的话，缓存只能读。

2. MyBatis3分页

1) 逻辑分页；(org.apache.ibatis.session.RowBounds)；
2) 物理分页；

package com.andrew.mappers;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.session.RowBounds;
import com.andrew.model.Student;
public interface StudentMapper {
    public List<Student> searchStudents(Map<String,Object> map);
    public List<Student> searchStudents2(Map<String,Object> map);
    public List<Student> searchStudents3(Map<String,Object> map);
    public List<Student> searchStudents4(Map<String,Object> map);
    public List<Student> searchStudents5(Map<String,Object> map);
    public int updateStudent(Student student);
    public int insertStudent(Student student);
    public Student getStudentById(Integer id);
    public List<Student> searchStudents6(String name,int age);
    public List<Student> findStudents(RowBounds rowBounds);
    public List<Student> findStudents2(Map<String,Object> map);
}

<?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.andrew.mappers.StudentMapper">
    <!-- 
    1) size:表示缓存cache中能容纳的最大元素数。默认是1024；
    2) flushInterval:定义缓存刷新周期，以毫秒计；
    3) eviction:定义缓存的移除机制；默认是LRU(leastrecentlyuserd，最近最少使用),还有FIFO(firstinfirstout，先进先出)    
    4) readOnly:默认值是false，假如是true的话，缓存只能读。
     -->
    <cache size="1024" flushInterval="60000" eviction="LRU" readOnly="false"/>
    <resultMap type="Student" id="StudentResult">
        <id property="id" column="id"/>
        <result property="name" column="name"/>
        <result property="age" column="age"/>
    </resultMap>
    ...
    <select id="findStudents" resultMap="StudentResult" flushCache="false" useCache="true">
        select * from t_student
    </select>
    <select id="findStudents2" parameterType="Map" resultMap="StudentResult">
        select * from t_student
        <if test="start!=null and size!=null">
            limit #{start},#{size}
        </if>
    </select>
</mapper>

package com.andrew.service;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.session.RowBounds;
import org.apache.ibatis.session.SqlSession;
import org.apache.log4j.Logger;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.andrew.mappers.StudentMapper;
import com.andrew.model.Student;
import com.andrew.util.SqlSessionFactoryUtil;
public class StudentPageTest {
    private SqlSession sqlSession = null;
    private StudentMapper studentMapper = null;
    @Before
    public void setUp() throws Exception {
        sqlSession = SqlSessionFactoryUtil.openSession();
        studentMapper = sqlSession.getMapper(StudentMapper.class);
    }
    @After
    public void tearDown() throws Exception {
        sqlSession.close();
    }
    @Test
    public void testFindStudent() {
        // 逻辑分页
        int offset = 0, limit = 3;
        RowBounds rowBounds = new RowBounds(offset, limit);
        List<Student> studentList = studentMapper.findStudents(rowBounds);
        for (Student student : studentList) {
            System.out.println(student);
        }
    }
    @Test
    public void testFindStudent2() {
        // 物理分页
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("start", 0);
        map.put("size", 10);
        List<Student> studentList = studentMapper.findStudents2(map);
        for (Student student : studentList) {
            System.out.println(student);
        }
    }
}