MyBatis入门（五）---延时加载、缓存

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','[e-mail]','张三是个新手，刚开始注册','2015-10-29 10:23:59'),(2,'李四','123asf','[e-mail]','魂牵梦萦 ','2015-10-29 10:24:29'),(3,'王五','dfsd342','[e-mail]','康熙王朝','2015-10-29 10:25:23'),(4,'赵六','123098sdfa','[e-mail]','花午骨','2015-10-29 10:26:09'),(5,'钱七','zxasqw','[e-mail]','这家伙很赖，什么也没留下','2015-10-29 10:27:04'),(6,'张三丰','123456','[e-mail]','这家伙很赖，什么也没留下','2015-10-29 11:48:00'),(7,'张无忌','qwertyuiop','[e-mail]','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','[e-mail]','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

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: 1Author [authorId=1, authorUserName=张三, authorPassword=123456, authorEmail=[e-mail], 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: 1Author [authorId=2, authorUserName=李四, authorPassword=123asf, authorEmail=[e-mail], authroBio=魂牵梦萦 , registerTime=Thu Oct 29 10:24:29 CST 2015]
Author [authorId=2, authorUserName=李四, authorPassword=123asf, authorEmail=[e-mail], 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: 1Author [authorId=4, authorUserName=赵六, authorPassword=123098sdfa, authorEmail=[e-mail], 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("[e-mail]");
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: 1Author [authorId=2, authorUserName=李四, authorPassword=123asf, authorEmail=[e-mail], 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), [e-mail](String), 射雕英雄传(String)
DEBUG [main] - <== Updates: 1DEBUG [main] - Committing JDBC Connection [com.mysql.jdbc.JDBC4Connection@42bb0406]11num=1再次查询
DEBUG [main] - ==> Preparing: select * from author where author_id=? DEBUG [main] - ==> Parameters: 2(Integer)
DEBUG [main] - <== Total: 1Author [authorId=2, authorUserName=李四, authorPassword=123asf, authorEmail=[e-mail], 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

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

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]: 0.0DEBUG [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: 1DEBUG [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]: 0.0DEBUG [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: 1DEBUG [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]: 0.5DEBUG [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), [e-mail](String), 公司(String), 2015-10-29 10:24:29.0(Timestamp), 2(Integer)
DEBUG [main] - <== Updates: 1DEBUG [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]: 0.3333333333333333DEBUG [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: 1DEBUG [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

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]: 0.0DEBUG [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: 1DEBUG [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]: 0.5DEBUG [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), [e-mail](String), 公司(String), 2015-10-29 10:24:29.0(Timestamp), 2(Integer)
DEBUG [main] - <== Updates: 1DEBUG [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]: 0.3333333333333333DEBUG [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: 1DEBUG [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.

以上就是MyBatis入门（五）---延时加载、缓存的内容，更多相关内容请关注PHP中文网（www.php.cn）！