MyBatis入门（五）---延时加载、缓存

时间：2015-11-01 16:25:02 阅读：300 评论：0 收藏：0 [点我收藏+]

标签：

一、创建数据库

1.1、建立数据库

/*
SQLyog Enterprise v12.09 (64 bit)
MySQL - 5.7.9-log : Database - mybatis
*********************************************************************
*/


/*!40101 SET NAMES utf8 */;

/*!40101 SET SQL_MODE=‘‘*/;

/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE=‘NO_AUTO_VALUE_ON_ZERO‘ */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;
CREATE DATABASE /*!32312 IF NOT EXISTS*/`mybatis` /*!40100 DEFAULT CHARACTER SET utf8 */;

USE `mybatis`;

/*Table structure for table `author` */

DROP TABLE IF EXISTS `author`;

CREATE TABLE `author` (
  `author_id` int(11) unsigned NOT NULL AUTO_INCREMENT COMMENT ‘作者ID主键‘,
  `author_username` varchar(30) NOT NULL COMMENT ‘作者用户名‘,
  `author_password` varchar(32) NOT NULL COMMENT ‘作者密码‘,
  `author_email` varchar(50) NOT NULL COMMENT ‘作者邮箱‘,
  `author_bio` varchar(1000) DEFAULT ‘这家伙很赖，什么也没留下‘ COMMENT ‘作者简介‘,
  `register_time` datetime DEFAULT CURRENT_TIMESTAMP COMMENT ‘注册时间‘,
  PRIMARY KEY (`author_id`)
) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8;

/*Data for the table `author` */

insert  into `author`(`author_id`,`author_username`,`author_password`,`author_email`,`author_bio`,`register_time`) values (1,‘张三‘,‘123456‘,‘123@qq.com‘,‘张三是个新手，刚开始注册‘,‘2015-10-29 10:23:59‘),(2,‘李四‘,‘123asf‘,‘lisi@163.com‘,‘魂牵梦萦 ‘,‘2015-10-29 10:24:29‘),(3,‘王五‘,‘dfsd342‘,‘ww@sina.com‘,‘康熙王朝‘,‘2015-10-29 10:25:23‘),(4,‘赵六‘,‘123098sdfa‘,‘zhaoliu@qq.com‘,‘花午骨‘,‘2015-10-29 10:26:09‘),(5,‘钱七‘,‘zxasqw‘,‘qianqi@qq.com‘,‘这家伙很赖，什么也没留下‘,‘2015-10-29 10:27:04‘),(6,‘张三丰‘,‘123456‘,‘zhangsf@qq.com‘,‘这家伙很赖，什么也没留下‘,‘2015-10-29 11:48:00‘),(7,‘张无忌‘,‘qwertyuiop‘,‘wuji@163.com‘,‘这家伙很赖，什么也没留下‘,‘2015-10-29 11:48:24‘),(8,‘fdsf‘,‘ffff‘,‘fdsfds‘,NULL,NULL),(9,‘fdsf‘,‘ffff‘,‘fdsfds‘,NULL,NULL),(10,‘aaaa‘,‘bbbb‘,‘ddd@qq.com‘,‘这家伙很赖，什么也没留下‘,‘2015-10-29 22:07:45‘);

/*Table structure for table `blog` */

DROP TABLE IF EXISTS `blog`;

CREATE TABLE `blog` (
  `blog_id` int(11) unsigned NOT NULL AUTO_INCREMENT COMMENT ‘BlogId主键‘,
  `blog_title` varchar(255) NOT NULL COMMENT ‘blog标题‘,
  `author_id` int(11) unsigned NOT NULL COMMENT ‘作者ID外键‘,
  PRIMARY KEY (`blog_id`),
  KEY `fk_author_id` (`author_id`),
  CONSTRAINT `fk_author_id` FOREIGN KEY (`author_id`) REFERENCES `author` (`author_id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;

/*Data for the table `blog` */

insert  into `blog`(`blog_id`,`blog_title`,`author_id`) values (1,‘小张的Blog‘,1),(2,‘小李‘,2),(3,‘王五不是人‘,3),(4,‘赵地人‘,4),(5,‘钱钱钱‘,5);

/*Table structure for table `posts` */

DROP TABLE IF EXISTS `posts`;

CREATE TABLE `posts` (
  `post_id` int(11) unsigned NOT NULL AUTO_INCREMENT COMMENT ‘文章主键ID‘,
  `post_subject` varchar(255) NOT NULL COMMENT ‘文章主题，标题‘,
  `post_body` text NOT NULL COMMENT ‘文章内容最大3000个字符‘,
  `blog_id` int(11) unsigned NOT NULL COMMENT ‘Blog主键做外键‘,
  `createtime` datetime DEFAULT CURRENT_TIMESTAMP COMMENT ‘文章创建时间‘,
  PRIMARY KEY (`post_id`),
  KEY `fk_blog_id` (`blog_id`),
  CONSTRAINT `fk_blog_id` FOREIGN KEY (`blog_id`) REFERENCES `blog` (`blog_id`)
) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8mb4;

/*Data for the table `posts` */

insert  into `posts`(`post_id`,`post_subject`,`post_body`,`blog_id`,`createtime`) values (1,‘Mybatis入门一‘,‘什么是 MyBatis ？\r\nMyBatis 是支持定制化 SQL、存储过程以及高级映射的优秀的持久层框架。MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。MyBatis 可以对配置和原生Map使用简单的 XML 或注解，将接口和 Java 的 POJOs(Plain Old Java Objects,普通的 Java对象)映射成数据库中的记录。‘,1,‘2015-10-29 10:32:21‘),(2,‘Mybatis入门二‘,‘要使用 MyBatis， 只需将 mybatis-x.x.x.jar 文件置于 classpath 中即可。‘,1,‘2015-10-29 10:32:52‘),(3,‘Oracle学习‘,‘Oracle Database，又名Oracle RDBMS，或简称Oracle。是甲骨文公司的一款关系数据库管理系统‘,2,‘2015-10-29 10:33:26‘),(4,‘JAVA学习一‘,‘Java是由Sun Microsystems公司于1995年5月推出的Java面向对象程序设计语言和Java平台的总称‘,3,‘2015-10-29 10:34:17‘),(5,‘PL/SQL‘,‘PL/SQL也是一种程序语言，叫做过程化SQL语言（Procedural Language/SQL）。PL/SQL是Oracle数据库对SQL语句的扩展‘,4,‘2015-10-29 10:37:52‘),(6,‘CSS标签选择器‘,‘标签选择器\r\nID选择器\r\n类选择器\r\n特殊选择器‘,5,‘2015-10-29 10:39:44‘),(7,‘javascript‘,‘js:是前端脚本语言‘,2,‘2015-10-29 10:40:18‘);

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

数据表和数据

二、创建项目

2.1、创建项目

技术分享

三、建立实体类与Mapper接口

3.1、3个实体类

package com.pb.mybatis.po;

import java.util.Date;

/**
 * 

* @ClassName: Author

* @Description: TODO(作者)

* @author 刘楠

* @date 2015-10-31 下午12:39:33

*
 */
public class Author {

    //作者id
    private Integer authorId;
    //作者姓名
    private String authorUserName;
    //作者密码
    private String authorPassword;
    //作者邮箱
    private String authorEmail;
    //作者介绍
    private String authroBio;
    //注册时间
    private Date registerTime;
    
    
    
    public Integer getAuthorId() {
        return authorId;
    }
    public void setAuthorId(Integer authorId) {
        this.authorId = authorId;
    }
    public String getAuthorUserName() {
        return authorUserName;
    }
    public void setAuthorUserName(String authorUserName) {
        this.authorUserName = authorUserName;
    }
    public String getAuthorPassword() {
        return authorPassword;
    }
    public void setAuthorPassword(String authorPassword) {
        this.authorPassword = authorPassword;
    }
    public String getAuthorEmail() {
        return authorEmail;
    }
    public void setAuthorEmail(String authorEmail) {
        this.authorEmail = authorEmail;
    }
    public String getAuthroBio() {
        return authroBio;
    }
    public void setAuthroBio(String authroBio) {
        this.authroBio = authroBio;
    }
    public Date getRegisterTime() {
        return registerTime;
    }
    public void setRegisterTime(Date registerTime) {
        this.registerTime = registerTime;
    }
    @Override
    public String toString() {
        return "Author [authorId=" + authorId + ", authorUserName="
                + authorUserName + ", authorPassword=" + authorPassword
                + ", authorEmail=" + authorEmail + ", authroBio=" + authroBio
                + ", registerTime=" + registerTime + "]";
    }
    
    
}

package com.pb.mybatis.po;

import java.util.List;



public class Blog {
    
    //Blog,ID
    private Integer blogId;
    //Blog 名称标题
    private String blogTitle;
    //外键authorId
    //作者
    private Author author;
    //文章 列表
    private Integer authorId;
    
    //文章列表
    private List<Posts> postsList;
    
    
    public Integer getBlogId() {
        return blogId;
    }
    public void setBlogId(Integer blogId) {
        this.blogId = blogId;
    }
    public String getBlogTitle() {
        return blogTitle;
    }
    public void setBlogTitle(String blogTitle) {
        this.blogTitle = blogTitle;
    }
    public Author getAuthor() {
        return author;
    }
    public void setAuthor(Author author) {
        this.author = author;
    }
    public Integer getAuthorId() {
        return authorId;
    }
    public void setAuthorId(Integer authorId) {
        this.authorId = authorId;
    }

    public List<Posts> getPostsList() {
        return postsList;
    }
    public void setPostsList(List<Posts> postsList) {
        this.postsList = postsList;
    }
    
    
    @Override
    public String toString() {
        return "Blog [blogId=" + blogId + ", blogTitle=" + blogTitle
                +  ", authorId=" + authorId + "]";
    }
    
    

    
    
    

}

package com.pb.mybatis.po;

import java.util.Date;

public class Posts {

    //文章ID
    private Integer postId;
    //文章标题
    private String postTitle;
    //文章主体内容
    private String postBody;
    
    //外键
    private Integer blogId;
    //建立时间
    private Date createTime;
    
    
    public Integer getPostId() {
        return postId;
    }
    public void setPostId(Integer postId) {
        this.postId = postId;
    }
    public String getPostTitle() {
        return postTitle;
    }
    public void setPostTitle(String postTitle) {
        this.postTitle = postTitle;
    }
    public String getPostBody() {
        return postBody;
    }
    public void setPostBody(String postBody) {
        this.postBody = postBody;
    }
    public Date getCreateTime() {
        return createTime;
    }
    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }
    
    
    public Integer getBlogId() {
        return blogId;
    }
    public void setBlogId(Integer blogId) {
        this.blogId = blogId;
    }
    @Override
    public String toString() {
        return "Posts [postId=" + postId + ", postTitle=" + postTitle
                + ", postBody=" + postBody + ", createTime=" + createTime
                + ", blogId=" + blogId + "]";
    }
    
    
    
    
    
    
}

3.2、3个接口

package com.pb.mybatis.mapper;

import com.pb.mybatis.po.Author;

public interface AuthorMapper {

    /**
     * 
    
    * @Title: findAuthorById
    
    * @Description: TODO(根据id查找)
    
    * @param @param id
    * @param @return    设定文件
    
    * @return Author    返回类型
    
    * @throws
     */
    public Author findAuthorById(int id);
}

package com.pb.mybatis.mapper;

import com.pb.mybatis.po.Blog;


public interface BlogMapper {
    
    /**
     * 
    
    * @Title: findBlogById
    
    * @Description: TODO(根据BLOGID查找BLOG，并关联author，与posts实现延时加载)
    
    * @param @param id
    * @param @return    设定文件
    
    * @return Blog    返回类型
    
    * @throws
     */
    public Blog findBlogById(int blogId);

}

package com.pb.mybatis.mapper;

import java.util.List;

import com.pb.mybatis.po.Posts;

public interface PostsMapper {

    /**
     * 
    
    * @Title: findPostsByBlogId
    
    * @Description: TODO(根据BLOGID查找文章列表)
    
    * @param @param blogId
    * @param @return    设定文件
    
    * @return List<Posts>    返回类型
    
    * @throws
     */
    public List<Posts> findPostsByBlogId(int blogId);
}

四、建立mapper.xml与confinguration.xml

4.1、相对应的mapper.xml

AuthorMapper.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.pb.mybatis.mapper.AuthorMapper">
<!--映射作者Author  -->
<resultMap type="Author" id="authorResultMap">
<id property="authorId" column="author_id"/>
<result property="authorUserName" column="author_username"/>
<result property="authorPassword" column="author_password"/>
<result property="authorEmail" column="author_email"/>
<result property="authroBio" column="author_bio"/>
<result property="registerTime" column="register_time"/>
</resultMap>
<!-- 根据ID查找 -->
<select id="findAuthorById" parameterType="int" resultMap="authorResultMap">
select * from author
where author_id=#{id}
</select>
</mapper>

BlogMapper.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.pb.mybatis.mapper.BlogMapper">
<!--Blog映射  -->
<resultMap type="Blog" id="blogResultMap">
<!--Blog映射  -->
<id property="blogId" column="blog_id"/>
<result property="blogTitle" column="blog_title"/>
<result property="authorId" column="author_id"/>

<!--一对一  -->
<association property="author" javaType="Author" column="author_id" select="com.pb.mybatis.mapper.AuthorMapper.findAuthorById"/>
<!--关联作者  
外键
column：外键
select:引用Authro的namespace.方法
-->

<!--一对多  ofType属性指定集合中元素的对象类型。-->
<collection property="postsList"  ofType="Posts" javaType="ArrayList"  column="blog_id" select="com.pb.mybatis.mapper.PostsMapper.findPostsByBlogId"/>
</resultMap>

<!-- 根据ID查找 -->
<select id="findBlogById" parameterType="int" resultMap="blogResultMap">
SELECT * FROM blog
WHERE blog_id=#{blogId}
</select>
</mapper>

PostsMapper.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.pb.mybatis.mapper.PostsMapper">
<!--映射作者文章  -->
<resultMap type="Posts" id="postsResultMap">
<id property="postId" column="post_id"/>
<result property="postTitle" column="post_subject"/>
<result property="postBody" column="post_body"/>
<result property="blogId" column="blog_id"/>
<result property="createTime" column="createtime"/>
</resultMap>
<!-- 根据ID查找 -->
<select id="findPostsByBlogId" parameterType="int" resultMap="postsResultMap">
select * from posts
where blog_id=#{blogId}
</select>
</mapper>

4.2、configuration.xml

db.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?character=utf8
username=root
password=root

开启延时加载，同时关闭立即加载

<settings>
<!--开启延时加载  -->
<setting name="lazyLoadingEnabled" value="true"/>
<!--关闭立即加载  -->
<setting name="aggressiveLazyLoading" value="false"/>
</settings>

<?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>
<!--资源文件  -->
<properties resource="db.properties"/>

<settings>
<!--开启延时加载  -->
<setting name="lazyLoadingEnabled" value="true"/>
<!--关闭立即加载  -->
<setting name="aggressiveLazyLoading" value="false"/>
</settings>
<!-- 别名  -->
<typeAliases>
<!-- <typeAlias type="com.pb.mybatis.po.User" alias="User"/> -->
<package name="com.pb.mybatis.po"/>
</typeAliases>
<!--配置  -->

<environments default="development">
<environment id="development">
    <!--事务  -->
    <transactionManager type="JDBC"/>
    <!--数据源  -->
    <dataSource type="POOLED">
    <property name="driver" value="${driver}"/>
    <property name="url" value="${url}"/>
    <property name="username" value="${username}"/>
    <property name="password" value="${password}"/>
    </dataSource>
</environment>
</environments>
<mappers>
    <package name="com.pb.mybatis.mapper"/>
</mappers>
</configuration>

五、测试

5.1、JUNIT

package com.pb.mybatis.mapper;

import java.io.InputStream;
import java.util.List;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Test;

import com.pb.mybatis.po.Blog;
import com.pb.mybatis.po.Posts;

public class BlogMapperTest {
    private SqlSessionFactory sqlSessionFactory;

    @Before
    public void setUp() throws Exception {
        String config="configuration.xml";
        InputStream resource=Resources.getResourceAsStream(config);
        sqlSessionFactory=new SqlSessionFactoryBuilder().build(resource);
    }

    /**
     * 
    
    * @Title: testFindBlogs
    
    * @Description: TODO(延时加载)
    
    * @param     设定文件
    
    * @return void    返回类型
    
    * @throws
     */
    @Test
    public void testFindBlogById() {
        //建立会话
        SqlSession sqlSession=sqlSessionFactory.openSession();
        //获取Mapper接口对象
        BlogMapper blogMapper=sqlSession.getMapper(BlogMapper.class);
        //调用Mapper方法 
        Blog blog=blogMapper.findBlogById(1);
        
        System.out.println(blog.getBlogId()+"..."+blog.getBlogTitle());
        System.out.println("===========开始延时加载作者Author===========");
        System.out.println(blog.getAuthor());
        System.out.println("===========开始延时加载文章===========");
        List<Posts> list=blog.getPostsList();
        /*int count=0;
        for(Posts p:list){
            System.out.println("count+"+count++);
            System.out.println(p.getPostId());
            System.out.println(p.getPostTitle());
            System.out.println(p.getPostBody());
            System.out.println(p.getCreateTime());
            System.out.println(p.getBlogId());
        }*/
        
    }

}

结果：

DEBUG [main] - ==>  Preparing: SELECT * FROM blog WHERE blog_id=? 
DEBUG [main] - ==> Parameters: 1(Integer)
DEBUG [main] - <==      Total: 1
1...小张的Blog
===========开始延时加载作者Author===========
DEBUG [main] - ==>  Preparing: select * from author where author_id=? 
DEBUG [main] - ==> Parameters: 1(Integer)
DEBUG [main] - <==      Total: 1
Author [authorId=1, authorUserName=张三, authorPassword=123456, authorEmail=123@qq.com, authroBio=张三是个新手，刚开始注册, registerTime=Thu Oct 29 10:23:59 CST 2015]
===========开始延时加载文章===========
DEBUG [main] - ==>  Preparing: select * from posts where blog_id=? 
DEBUG [main] - ==> Parameters: 1(Integer)
DEBUG [main] - <==      Total: 2

六、一级缓存

6.1、mybatis一级缓存

mybatis，默认开启了一级缓存，sqlSession中默认有一个hashMap

当查询时，先去hashMap中查找，

如果有就直接，取出，不再操作数据库

如果没有就去数据库查找，并放在haspMap中

当做事物时，如添加，删除，修改，后有commit时会清空一级缓存

sqlSession是互不影响的，一级缓存

6.2、还是上级的例子

测试:查询用户

package com.pb.mybatis.mapper;

import static org.junit.Assert.*;

import java.io.InputStream;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Test;

import com.pb.mybatis.po.Author;

public class AuthorMapperTest {
    private SqlSessionFactory sqlSessionFactory;

    @Before
    public void setUp() throws Exception {
        String config="configuration.xml";
        InputStream resource=Resources.getResourceAsStream(config);
        sqlSessionFactory=new SqlSessionFactoryBuilder().build(resource);
    }

    @Test
    public void testFindAuthorById() {
        //获取会话工厂
        SqlSession sqlSession=sqlSessionFactory.openSession();
        AuthorMapper authorMapper=sqlSession.getMapper(AuthorMapper.class);
        //第一次查询
        Author author1=authorMapper.findAuthorById(2);
        System.out.println(author1);
        //再次查询同样的
        Author author2=authorMapper.findAuthorById(2);
        System.out.println(author2);
        
        //再次查询不的同样的
        Author author3=authorMapper.findAuthorById(4);
        System.out.println(author3);
    }

}

结果：

DEBUG [main] - ==>  Preparing: select * from author where author_id=? 
DEBUG [main] - ==> Parameters: 2(Integer)
DEBUG [main] - <==      Total: 1
Author [authorId=2, authorUserName=李四, authorPassword=123asf, authorEmail=lisi@163.com, authroBio=魂牵梦萦 , registerTime=Thu Oct 29 10:24:29 CST 2015]
Author [authorId=2, authorUserName=李四, authorPassword=123asf, authorEmail=lisi@163.com, authroBio=魂牵梦萦 , registerTime=Thu Oct 29 10:24:29 CST 2015]
DEBUG [main] - ==>  Preparing: select * from author where author_id=? 
DEBUG [main] - ==> Parameters: 4(Integer)
DEBUG [main] - <==      Total: 1
Author [authorId=4, authorUserName=赵六, authorPassword=123098sdfa, authorEmail=zhaoliu@qq.com, authroBio=花午骨, registerTime=Thu Oct 29 10:26:09 CST 2015]

6.3、当查询后，做事务，再查询第一次的

接口中做添加方法

/**
     * 
    
    * @Title: addAuthor
    
    * @Description: TODO(添加)
    
    * @param @param author
    * @param @return    设定文件
    
    * @return int    返回类型
    
    * @throws
     */
    public int addAuthor(Author author);

mapper.xml中做同样的select

<!--添加  -->
<insert id="addAuthor" parameterType="Author" useGeneratedKeys="true" keyProperty="authorId">
INSERT INTO author(author_username,author_password,author_email,author_bio)
VALUES(#{authorUserName},#{authorPassword},#{authorEmail},#{authroBio})
</insert>

测试

package com.pb.mybatis.mapper;

import static org.junit.Assert.*;

import java.io.InputStream;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Test;

import com.pb.mybatis.po.Author;

public class AuthorMapperTest {
    private SqlSessionFactory sqlSessionFactory;

    @Before
    public void setUp() throws Exception {
        String config="configuration.xml";
        InputStream resource=Resources.getResourceAsStream(config);
        sqlSessionFactory=new SqlSessionFactoryBuilder().build(resource);
    }

    @Test
    public void testFindAuthorById() {
        //获取会话工厂
        SqlSession sqlSession=sqlSessionFactory.openSession();
        AuthorMapper authorMapper=sqlSession.getMapper(AuthorMapper.class);
        //第一次查询
        Author author1=authorMapper.findAuthorById(2);
        System.out.println(author1);
        System.out.println("=======下面有事务处理========");
        Author newAuthor=new Author();
        newAuthor.setAuthorEmail("qq.com@qq.com");
        newAuthor.setAuthorPassword("fdsfds");
        newAuthor.setAuthorUserName("郭靖");
        newAuthor.setAuthroBio("射雕英雄传");
        int num=authorMapper.addAuthor(newAuthor);
        sqlSession.commit();
        
        System.out.println(newAuthor.getAuthorId());
        System.out.println("num="+num);
        System.out.println("再次查询");
        //再次查询同样的
        Author author2=authorMapper.findAuthorById(2);
        System.out.println(author2);
    
    }

    

}

结果：

DEBUG [main] - ==>  Preparing: select * from author where author_id=? 
DEBUG [main] - ==> Parameters: 2(Integer)
DEBUG [main] - <==      Total: 1
Author [authorId=2, authorUserName=李四, authorPassword=123asf, authorEmail=lisi@163.com, authroBio=魂牵梦萦 , registerTime=Thu Oct 29 10:24:29 CST 2015]
=======下面有事务处理========
DEBUG [main] - ==>  Preparing: INSERT INTO author(author_username,author_password,author_email,author_bio) VALUES(?,?,?,?) 
DEBUG [main] - ==> Parameters: 郭靖(String), fdsfds(String), qq.com@qq.com(String), 射雕英雄传(String)
DEBUG [main] - <==    Updates: 1
DEBUG [main] - Committing JDBC Connection [com.mysql.jdbc.JDBC4Connection@42bb0406]
11
num=1
再次查询
DEBUG [main] - ==>  Preparing: select * from author where author_id=? 
DEBUG [main] - ==> Parameters: 2(Integer)
DEBUG [main] - <==      Total: 1
Author [authorId=2, authorUserName=李四, authorPassword=123asf, authorEmail=lisi@163.com, authroBio=魂牵梦萦 , registerTime=Thu Oct 29 10:24:29 CST 2015]

七、二级缓存

7.1、mybatis二级缓存与一级缓存

技术分享

sqlSession是互不影响的，一级缓存

Mapper(namespace)是二级缓存

多个sqlSession可以共享一个Mapper的二级缓存区域

二级缓存按namespace分，其它的mapper也有自己的二级缓存区域namespace

第一个namespace的mapper都有一个二级缓存区域，2个mapper的namespace如果相同，这2个mapper执行sql查询数据将存在相同的二级缓存区域中.

7.2、开启二级缓存

1.二级缓存是mapper范围级别的，除了在configuration.xml设置二级缓存的总开关，还在在个体的mapper.xml中开启二级缓存

<settings>
<!--开启延时加载  -->
<setting name="lazyLoadingEnabled" value="true"/>
<!--关闭立即加载  -->
<setting name="aggressiveLazyLoading" value="false"/>
<!--开启二级缓存  -->
<setting name="cacheEnabled" value="true" />
</settings>

2.mapper对就的pojo类，实现序列化

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3.在authorMapper中开启二级缓存

<!--开启本mapper下的二级缓冲  -->
<cache />

7.3、测试

@Test
    public void testCache() {
        // 获取会话工厂
        SqlSession sqlSession1 = sqlSessionFactory.openSession();
        AuthorMapper authorMapper1 = sqlSession1.getMapper(AuthorMapper.class);
        // 第一次查询
        Author author1 = authorMapper1.findAuthorById(2);
        //必须关闭不数据无法写到缓存区域
        sqlSession1.close();

        // 获取会话工厂
        /*SqlSession sqlSession2 = sqlSessionFactory.openSession();
        AuthorMapper authorMapper2 = sqlSession2.getMapper(AuthorMapper.class);
        sqlSession2.close();*/
        // 获取会话工厂
        SqlSession sqlSession3 = sqlSessionFactory.openSession();
        AuthorMapper authorMapper3 = sqlSession3.getMapper(AuthorMapper.class);
        // 第一次查询
        Author author3 = authorMapper3.findAuthorById(2);
        sqlSession3.close();
    }

DEBUG [main] - Cache Hit Ratio [com.pb.mybatis.mapper.AuthorMapper]: 0.0
DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Created connection 873769339.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@3414a97b]
DEBUG [main] - ==>  Preparing: select * from author where author_id=? 
DEBUG [main] - ==> Parameters: 2(Integer)
DEBUG [main] - <==      Total: 1
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@3414a97b]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@3414a97b]
DEBUG [main] - Returned connection 873769339 to pool.
DEBUG [main] - Cache Hit Ratio [com.pb.mybatis.mapper.AuthorMapper]: 0.5

中间增加commit操作

@Test
    public void testCache() {
        // 获取会话工厂
        SqlSession sqlSession1 = sqlSessionFactory.openSession();
        AuthorMapper authorMapper1 = sqlSession1.getMapper(AuthorMapper.class);
        // 第一次查询
        Author author1 = authorMapper1.findAuthorById(2);
        //必须关闭不数据无法写到缓存区域
        sqlSession1.close();

        // 获取会话工厂
        SqlSession sqlSession2 = sqlSessionFactory.openSession();
        AuthorMapper authorMapper2 = sqlSession2.getMapper(AuthorMapper.class);
        Author author2 = authorMapper2.findAuthorById(2);
        //更新
        author2.setAuthorUserName("董事长");
        author2.setAuthroBio("公司");
        authorMapper2.updateAuthor(author2);
        //commit会清空缓存区域
        sqlSession2.commit();
        sqlSession2.close();
        // 获取会话工厂
        SqlSession sqlSession3 = sqlSessionFactory.openSession();
        AuthorMapper authorMapper3 = sqlSession3.getMapper(AuthorMapper.class);
        // 第一次查询
        Author author3 = authorMapper3.findAuthorById(2);
        sqlSession3.close();
    }

结果：

DEBUG [main] - Cache Hit Ratio [com.pb.mybatis.mapper.AuthorMapper]: 0.0
DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Created connection 873769339.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@3414a97b]
DEBUG [main] - ==>  Preparing: select * from author where author_id=? 
DEBUG [main] - ==> Parameters: 2(Integer)
DEBUG [main] - <==      Total: 1
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@3414a97b]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@3414a97b]
DEBUG [main] - Returned connection 873769339 to pool.
DEBUG [main] - Cache Hit Ratio [com.pb.mybatis.mapper.AuthorMapper]: 0.5
DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Checked out connection 873769339 from pool.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@3414a97b]
DEBUG [main] - ==>  Preparing: update author SET author_username=?, author_password=?, author_email=?, author_bio=?, register_time=? where author_id=? 
DEBUG [main] - ==> Parameters: 董事长(String), 123asf(String), lisi@163.com(String), 公司(String), 2015-10-29 10:24:29.0(Timestamp), 2(Integer)
DEBUG [main] - <==    Updates: 1
DEBUG [main] - Committing JDBC Connection [com.mysql.jdbc.JDBC4Connection@3414a97b]
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@3414a97b]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@3414a97b]
DEBUG [main] - Returned connection 873769339 to pool.
DEBUG [main] - Cache Hit Ratio [com.pb.mybatis.mapper.AuthorMapper]: 0.3333333333333333
DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Checked out connection 873769339 from pool.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@3414a97b]
DEBUG [main] - ==>  Preparing: select * from author where author_id=? 
DEBUG [main] - ==> Parameters: 2(Integer)
DEBUG [main] - <==      Total: 1
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@3414a97b]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@3414a97b]
DEBUG [main] - Returned connection 873769339 to pool.

八、Mybatis与ehcache整合

8.1、把jar包导入项目

技术分享

8.2、建立ehcache.xml

ehcache.xml

<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:noNamespaceSchemaLocation="../config/ehcache.xsd">
    <diskStore path="F:\develop\ehcache" />
    <defaultCache 
        maxElementsInMemory="1000" 
        maxElementsOnDisk="10000000"
        eternal="false" 
        overflowToDisk="false" 
        timeToIdleSeconds="120"
        timeToLiveSeconds="120" 
        diskExpiryThreadIntervalSeconds="120"
        memoryStoreEvictionPolicy="LRU">
    </defaultCache>
</ehcache>

8.3、在mapper的cache中指定type

<!--开启本mapper下的二级缓冲 
type指定为ehcachecache类开
在ehcache和mybatis的整合包中
 -->
<cache type="org.mybatis.caches.ehcache.EhcacheCache"/>

8.4、测试

@Test
    public void testCache() {
        // 获取会话工厂
        SqlSession sqlSession1 = sqlSessionFactory.openSession();
        AuthorMapper authorMapper1 = sqlSession1.getMapper(AuthorMapper.class);
        // 第一次查询
        Author author1 = authorMapper1.findAuthorById(2);
        //必须关闭不数据无法写到缓存区域
        sqlSession1.close();

        // 获取会话工厂
        SqlSession sqlSession2 = sqlSessionFactory.openSession();
        AuthorMapper authorMapper2 = sqlSession2.getMapper(AuthorMapper.class);
        Author author2 = authorMapper2.findAuthorById(2);
        //更新
        author2.setAuthorUserName("董事长");
        author2.setAuthroBio("公司");
        authorMapper2.updateAuthor(author2);
        //commit会清空缓存区域
        sqlSession2.commit();
        sqlSession2.close();
        // 获取会话工厂
        SqlSession sqlSession3 = sqlSessionFactory.openSession();
        AuthorMapper authorMapper3 = sqlSession3.getMapper(AuthorMapper.class);
        // 第一次查询
        Author author3 = authorMapper3.findAuthorById(2);
        sqlSession3.close();
    }

结果：

DEBUG [main] - Configuring ehcache from ehcache.xml found in the classpath: file:/E:/mywork/MybatisDemo2/bin/ehcache.xml
DEBUG [main] - Configuring ehcache from URL: file:/E:/mywork/MybatisDemo2/bin/ehcache.xml
DEBUG [main] - Configuring ehcache from InputStream
DEBUG [main] - Ignoring ehcache attribute xmlns:xsi
DEBUG [main] - Ignoring ehcache attribute xsi:noNamespaceSchemaLocation
DEBUG [main] - Disk Store Path: F:\develop\ehcache
DEBUG [main] - Creating new CacheManager with default config
DEBUG [main] - propertiesString is null.
DEBUG [main] - No CacheManagerEventListenerFactory class specified. Skipping...
DEBUG [main] - No BootstrapCacheLoaderFactory class specified. Skipping...
DEBUG [main] - CacheWriter factory not configured. Skipping...
DEBUG [main] - No CacheExceptionHandlerFactory class specified. Skipping...
DEBUG [main] - Initialized net.sf.ehcache.store.NotifyingMemoryStore for com.pb.mybatis.mapper.AuthorMapper
DEBUG [main] - Initialised cache: com.pb.mybatis.mapper.AuthorMapper
DEBUG [main] - CacheDecoratorFactory not configured for defaultCache. Skipping for ‘com.pb.mybatis.mapper.AuthorMapper‘.
DEBUG [main] - Cache Hit Ratio [com.pb.mybatis.mapper.AuthorMapper]: 0.0
DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Created connection 1286943672.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@4cb533b8]
DEBUG [main] - ==>  Preparing: select * from author where author_id=? 
DEBUG [main] - ==> Parameters: 2(Integer)
DEBUG [main] - <==      Total: 1
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@4cb533b8]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@4cb533b8]
DEBUG [main] - Returned connection 1286943672 to pool.
DEBUG [main] - Cache Hit Ratio [com.pb.mybatis.mapper.AuthorMapper]: 0.5
DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Checked out connection 1286943672 from pool.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@4cb533b8]
DEBUG [main] - ==>  Preparing: update author SET author_username=?, author_password=?, author_email=?, author_bio=?, register_time=? where author_id=? 
DEBUG [main] - ==> Parameters: 董事长(String), 123asf(String), lisi@163.com(String), 公司(String), 2015-10-29 10:24:29.0(Timestamp), 2(Integer)
DEBUG [main] - <==    Updates: 1
DEBUG [main] - Committing JDBC Connection [com.mysql.jdbc.JDBC4Connection@4cb533b8]
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@4cb533b8]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@4cb533b8]
DEBUG [main] - Returned connection 1286943672 to pool.
DEBUG [main] - Cache Hit Ratio [com.pb.mybatis.mapper.AuthorMapper]: 0.3333333333333333
DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Checked out connection 1286943672 from pool.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@4cb533b8]
DEBUG [main] - ==>  Preparing: select * from author where author_id=? 
DEBUG [main] - ==> Parameters: 2(Integer)
DEBUG [main] - <==      Total: 1
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@4cb533b8]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@4cb533b8]
DEBUG [main] - Returned connection 1286943672 to pool.

MyBatis入门（五）---延时加载、缓存

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原文地址：http://www.cnblogs.com/liunanjava/p/4925553.html

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