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Mybatis简介

Mybatis简介

作者: 默默无痕 | 来源:发表于2017-06-28 21:44 被阅读0次

    Mybatis的前身是iBatis,iBatis原本就是apache的一个开源项目,2010年该项目有apache迁移到了google code,并改名为MyBatis。

    1. 简介

    MyBatis支持普通SQL查询,存储过程和高级映射的优秀持久层框架,消除了几乎所有的JDBC代码和参数的手动设置以及结果集的检索。MyBatis可以使用XML或者注解用于配置和映射,将接口和JavaBean映射成数据库的记录。

    每一个MyBatis的应用程序都以一个SqlSessionFactory对象的实例为核心。SqlSessionFactory对象的实例可以通过SqlSessionFactoryBuilder对象来获得,SqlSessionFactoryBuilder对象可以从XML配置文件或从Configuration类获得。例如:

    String resource ="com/alvinliang/mybatis/mybatis-config.xml";
    InputStreamis= Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory =newSqlSessionFactoryBuilder().build(is);
    

    XML配置文件包含了对MyBatis系统的核心设置,有获取数据库连接实例的数据源和决定事务范围和控制事务管理器。详细内容后面会讲,这里给出一个简单示例:

    <?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>
      <environments default="development">
        <environment id="development">
          <transactionManager type="JDBC"/>
          <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>
        <mapper resource="com/alvinliang/mybatis/BlogMapper.xml"/>
      </mappers>
    </configuration>
    

    还有很多可以配置,上面指出了最关键的部分。environment元素体里包含对事务管理和连接池的环境配置。mapppers元素包含了所有mapper映射器,这些mapper的xml文件包含了SQL代码和映射定义信息。
    详细配置,见Mybatis官网

    2.总体流程

    (1) 加载配置并初始化

    触发条件:加载配置文件,将SQL配置文件加载成一个个MappedStatement对象。
    关于MappedStatement是Mybatis的几个重要类,详细见

    (2) 接受调用请求

    触发条件:调用MyBatis提供的API

    传入参数:为SQL的ID和传入参数对象

    处理过程:将请求传递给下层的请求的处理层进行处理。

    (3) 处理操作请求

    触发条件:API接口层传递请求过来

    传入参数:为SQL的ID和传入参数对象

    处理过程:

    (A)根据SQL的ID查找对应的MappedStatement对象。

    (B)根据传入参数对象解析MappedStatement对象,得到最终要执行的SQL和执行传入参数。

    (C)获取数据库连接,根据得到的最终SQL语句和执行传入参数到数据库执行,并得到执行结果。

    (D)根据MappedStatement对象中的结果映射配置对得到的执行结果进行转换处理,并得到最终的处理结果。

    (E)释放连接资源。

    (4)返回处理结果将最终的处理结果返回。

    3.功能框架

    Mybatis可以分为三层:

    (1) API接口层:提供给外部使用的接口API,开发人员可以通过本地API来操纵数据库。

    (2) 数据处理层:负责具体的SQL查找、SQL解析、SQL执行和执行结果映射处理等。

    (3) 基础支持层:负责最基本的功能支撑,包括连接管理、事务管理、配置加载和缓存处理等。

    4.简单使用

    先从SqlSessionFactory对象来获得SqlSession的实例,SqlSession对象包含了对数据库的所有执行SQL操作的方法。例如:

    SqlSession session = sqlSessionFactory.openSession();
    try {  
    Blogblog = (Blog) session.selectOne("com.alvinliang.mybatis.BlogMapper.selectBlog", 1);
    } finally {  
    session.close();
    }
    

    下面给出映射的SQL语句:

    <?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.alvinliang.mybatis.BlogMapper">
      <select id="selectBlog" resultType="Blog">
        select * from Blog where id = #{id}
      </select>
    </mapper>
    

    这里只是给出了一个简洁的例子,其中在命名空间“com.alvinliang.mybatis.BlogMapper”中定义了一个名为“selectBlog”的映射语句,这样它允许你使用完全限定名“com.alvinliang.mybatis.BlogMapper.selectBlog”来调用映射语句。

    注意:现在命名空间是必须的,而且命名空间使得接口绑定成为可能,使用命名空间并将它放在合适的Java包空间下,将会使你的代码变得简洁,会在很长的时间内提高MyBatis的作用。

    1. 范围和生命周期

    SqlSessionFactoryBuilder

    这个类可以被实例化,使用和丢弃。一旦你创建了SqlSessionFactory后,这个类就不需要了。因此SqlSessionFactoryBuilder实例的最佳范围就是方法范围(也就是本地方法变量)。你可以重用SqlSessionFactoryBuilder来创建多个SqlSessionFactory实例。

    SqlSessionFactory

    一旦被创建,SqlSessionFactory应该在你的应用执行期间都存在,没有理来处理或者重新创建它。使用SqlSessionFactory的最佳实践是在应用运行期间不要重复创建多次。因此SqlSessionFactory的生命周期是Application范围。很多方法可以做到,如单例模式或者静态单例模式。

    SqlSession

    每个线程都应该有它自己的SqlSession实例。SqlSession的实例不能被共享,也是线程不安全的。因此最佳范围应该是request或者method范围。绝对不能将SqlSession实例的引用放在一个类的静态字段甚至是实例字段中。也绝对不能将SqlSession实例引用放在任何类型的管理范围中,比如Servlet中的HttpSession。如果你正在使用Web框架,可以考虑将SqlSession放在一个和Http Request对象相似的范围内。下面的示例就是一个确保SqlSession关闭的基本模式:

    SqlSession session = sqlSessionFactory.openSession();
    try {
    // do work
    } finally {  
    session.close();
    }
    

    在你的代码中一贯的使用这种模式,将会保证所有的数据库资源都正常的关闭。

    完整的Example

    **Step1: **Create a Maven project and configure MyBatis dependencies.

    <project xmlns='http://maven.apache.org/POM/4.0.0' 
     xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'
     xsi:schemaLocation='http://maven.apache.org/POM/4.0.0 
     http://maven.apache.org/xsd/maven-4.0.0.xsd'>
     <modelVersion>4.0.0</modelVersion>
    
     <groupId>com.sivalabs</groupId>
     <artifactId>mybatis-demo</artifactId>
     <version>0.0.1-SNAPSHOT</version>
     <packaging>jar</packaging>
    
     <name>mybatis-demo</name>
     <url>http://maven.apache.org</url>
    
     <properties>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     </properties>
    
     <build>
      <plugins>
       <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>2.3.2</version>
        <configuration>
         <source>1.6</source>
         <target>1.6</target>
         <encoding>${project.build.sourceEncoding}</encoding>
        </configuration>
       </plugin>
      </plugins>
     </build>
    
     <dependencies>
      <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
       <version>4.10</version>
       <scope>test</scope>
      </dependency>
    
      <dependency>
          <groupId>org.mybatis</groupId>
          <artifactId>mybatis</artifactId>
          <version>3.1.1</version>
      </dependency>
      <dependency>
                 <groupId>mysql</groupId>
                 <artifactId>mysql-connector-java</artifactId>
                 <version>5.1.21</version>
                 <scope>runtime</scope>
             </dependency>
     </dependencies>
    </project>
    

    Step#2: Create the table USER and a Java domain Object User as follows:

    CREATE TABLE  user (
      user_id int(10) unsigned NOT NULL auto_increment,
      email_id varchar(45) NOT NULL,
      password varchar(45) NOT NULL,
      first_name varchar(45) NOT NULL,
      last_name varchar(45) default NULL,
      PRIMARY KEY  (user_id),
      UNIQUE KEY Index_2_email_uniq (email_id)
    ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
    
    package com.sivalabs.mybatisdemo.domain;
    public class User 
    {
     private Integer userId;
     private String emailId;
     private String password;
     private String firstName;
     private String lastName;
    
     @Override
     public String toString() {
      return 'User [userId=' + userId + ', emailId=' + emailId
        + ', password=' + password + ', firstName=' + firstName
        + ', lastName=' + lastName + ']';
     }
     //setters and getters 
    }
    

    Step#3: Create MyBatis configuration files.
    a) Create jdbc.properties file in src/main/resources folder

    jdbc.driverClassName=com.mysql.jdbc.Driver
    jdbc.url=jdbc:mysql://localhost:3306/mybatis-demo
    jdbc.username=root
    jdbc.password=admin
    

    b) Create mybatis-config.xml file in src/main/resources folder

    <?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>
     <properties resource='jdbc.properties'/>
     <typeAliases>
      <typeAlias type='com.sivalabs.mybatisdemo.domain.User' alias='User'></typeAlias>
     </typeAliases>
     <environments default='development'>
      <environment id='development'>
        <transactionManager type='JDBC'/>
        <dataSource type='POOLED'>    
       <property name='driver' value='${jdbc.driverClassName}'/>
       <property name='url' value='${jdbc.url}'/>
       <property name='username' value='${jdbc.username}'/>
       <property name='password' value='${jdbc.password}'/>
        </dataSource>
      </environment>
      </environments>
      <mappers>
     <mapper resource='com/sivalabs/mybatisdemo/mappers/UserMapper.xml'/>
      </mappers>
    </configuration>
    

    Step#4: Create an interface UserMapper.java in src/main/java folder in com.sivalabs.mybatisdemo.mappers package.

    package com.sivalabs.mybatisdemo.mappers;
    
    import java.util.List;
    import com.sivalabs.mybatisdemo.domain.User;
    
    public interface UserMapper 
    {
    
     public void insertUser(User user);
    
     public User getUserById(Integer userId);
    
     public List<User> getAllUsers();
    
     public void updateUser(User user);
    
     public void deleteUser(Integer userId);
    
    }
    

    Step#5: Create UserMapper.xml file in src/main/resources folder in com.sivalabs.mybatisdemo.mappers package.

    <?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.sivalabs.mybatisdemo.mappers.UserMapper'>
    
      <select id='getUserById' parameterType='int' resultType='com.sivalabs.mybatisdemo.domain.User'>
         SELECT 
          user_id as userId, 
          email_id as emailId , 
          password, 
          first_name as firstName, 
          last_name as lastName
         FROM USER 
         WHERE USER_ID = #{userId}
      </select>
      <!-- Instead of referencing Fully Qualified Class Names we can register Aliases in mybatis-config.xml and use Alias names. -->
       <resultMap type='User' id='UserResult'>
        <id property='userId' column='user_id'/>
        <result property='emailId' column='email_id'/>
        <result property='password' column='password'/>
        <result property='firstName' column='first_name'/>
        <result property='lastName' column='last_name'/>   
       </resultMap>
    
      <select id='getAllUsers' resultMap='UserResult'>
       SELECT * FROM USER
      </select>
    
      <insert id='insertUser' parameterType='User' useGeneratedKeys='true' keyProperty='userId'>
       INSERT INTO USER(email_id, password, first_name, last_name)
        VALUES(#{emailId}, #{password}, #{firstName}, #{lastName})
      </insert>
    
      <update id='updateUser' parameterType='User'>
        UPDATE USER 
        SET
         PASSWORD= #{password},
         FIRST_NAME = #{firstName},
         LAST_NAME = #{lastName}
        WHERE USER_ID = #{userId}
      </update>
    
      <delete id='deleteUser' parameterType='int'>
        DELETE FROM USER WHERE USER_ID = #{userId}
      </delete>
    
    </mapper>
    

    Step#6: Create MyBatisUtil.java to instantiate SqlSessionFactory.

    package com.sivalabs.mybatisdemo.service;
    
    import java.io.IOException;
    import java.io.Reader;
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    public class MyBatisUtil 
    {
     private static SqlSessionFactory factory;
    
     private MyBatisUtil() {
     }
    
     static
     {
      Reader reader = null;
      try {
       reader = Resources.getResourceAsReader('mybatis-config.xml');
      } catch (IOException e) {
       throw new RuntimeException(e.getMessage());
      }
      factory = new SqlSessionFactoryBuilder().build(reader);
     }
    
     public static SqlSessionFactory getSqlSessionFactory() 
     {
      return factory;
     }
    }
    

    Step#7: Create UserService.java in src/main/java folder.

    package com.sivalabs.mybatisdemo.service;
    
    import java.util.List;
    import org.apache.ibatis.session.SqlSession;
    import com.sivalabs.mybatisdemo.domain.User;
    import com.sivalabs.mybatisdemo.mappers.UserMapper;
    
    public class UserService
    {
    
     public void insertUser(User user) {
      SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
      try{
      UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
      userMapper.insertUser(user);
      sqlSession.commit();
      }finally{
       sqlSession.close();
      }
     }
    
     public User getUserById(Integer userId) {
      SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
      try{
      UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
      return userMapper.getUserById(userId);
      }finally{
       sqlSession.close();
      }
     }
    
     public List<User> getAllUsers() {
      SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
      try{
      UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
      return userMapper.getAllUsers();
      }finally{
       sqlSession.close();
      }
     }
    
     public void updateUser(User user) {
      SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
      try{
      UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
      userMapper.updateUser(user);
      sqlSession.commit();
      }finally{
       sqlSession.close();
      }
    
     }
    
     public void deleteUser(Integer userId) {
      SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
      try{
      UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
      userMapper.deleteUser(userId);
      sqlSession.commit();
      }finally{
       sqlSession.close();
      }
    
     }
    
    }
    

    Step#8: Create a JUnit Test class to test UserService methods.

    package com.sivalabs.mybatisdemo;
    
    import java.util.List;
    
    import org.junit.AfterClass;
    import org.junit.Assert;
    import org.junit.BeforeClass;
    import org.junit.Test;
    
    import com.sivalabs.mybatisdemo.domain.User;
    import com.sivalabs.mybatisdemo.service.UserService;
    
    public class UserServiceTest 
    {
     private static UserService userService;
    
     @BeforeClass
        public static void setup() 
     {
      userService = new UserService();
     }
    
     @AfterClass
        public static void teardown() 
     {
      userService = null;
     }
    
        @Test
     public void testGetUserById() 
     {
      User user = userService.getUserById(1);
      Assert.assertNotNull(user);
      System.out.println(user);
     }
    
        @Test
        public void testGetAllUsers() 
        {
      List<User> users = userService.getAllUsers();
      Assert.assertNotNull(users);
      for (User user : users) 
      {
       System.out.println(user);
      }
    
     }
    
        @Test
        public void testInsertUser() 
        {
         User user = new User();
         user.setEmailId('test_email_'+System.currentTimeMillis()+'@gmail.com');
         user.setPassword('secret');
         user.setFirstName('TestFirstName');
         user.setLastName('TestLastName');
    
         userService.insertUser(user);
      Assert.assertTrue(user.getUserId() != 0);
      User createdUser = userService.getUserById(user.getUserId());
      Assert.assertNotNull(createdUser);
      Assert.assertEquals(user.getEmailId(), createdUser.getEmailId());
      Assert.assertEquals(user.getPassword(), createdUser.getPassword());
      Assert.assertEquals(user.getFirstName(), createdUser.getFirstName());
      Assert.assertEquals(user.getLastName(), createdUser.getLastName());
    
     }
    
        @Test
        public void testUpdateUser() 
        {
         long timestamp = System.currentTimeMillis();
      User user = userService.getUserById(2);
      user.setFirstName('TestFirstName'+timestamp);
         user.setLastName('TestLastName'+timestamp);
         userService.updateUser(user);
      User updatedUser = userService.getUserById(2);
      Assert.assertEquals(user.getFirstName(), updatedUser.getFirstName());
      Assert.assertEquals(user.getLastName(), updatedUser.getLastName());
     }
    
       @Test
       public void testDeleteUser() 
       {
         User user = userService.getUserById(4);
         userService.deleteUser(user.getUserId());
      User deletedUser = userService.getUserById(4);
      Assert.assertNull(deletedUser);   
    
     }
    }
    

    Now, I will explain how to perform CRUD operations using MyBatis Annotation support without need of Queries configuration in XML mapper files.

    Step#1: Create a table BLOG and a java domain Object Blog.

    CREATE TABLE  blog (
      blog_id int(10) unsigned NOT NULL auto_increment,
      blog_name varchar(45) NOT NULL,
      created_on datetime NOT NULL,
      PRIMARY KEY  (blog_id)
    ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
    
    package com.sivalabs.mybatisdemo.domain;
    
    import java.util.Date;
    
    public class Blog {
    
     private Integer blogId;
     private String blogName;
     private Date createdOn;
    
     @Override
     public String toString() {
      return 'Blog [blogId=' + blogId + ', blogName=' + blogName
        + ', createdOn=' + createdOn + ']';
     }
     //Seeters and getters
    }
    

    Step#2: Create UserMapper.java interface with SQL queries in Annotations.

    package com.sivalabs.mybatisdemo.mappers;
    
    import java.util.List;
    
    import org.apache.ibatis.annotations.Delete;
    import org.apache.ibatis.annotations.Insert;
    import org.apache.ibatis.annotations.Options;
    import org.apache.ibatis.annotations.Result;
    import org.apache.ibatis.annotations.Results;
    import org.apache.ibatis.annotations.Select;
    import org.apache.ibatis.annotations.Update;
    
    import com.sivalabs.mybatisdemo.domain.Blog;
    
    public interface BlogMapper 
    {
     @Insert('INSERT INTO BLOG(BLOG_NAME, CREATED_ON) VALUES(#{blogName}, #{createdOn})')
     @Options(useGeneratedKeys=true, keyProperty='blogId')
     public void insertBlog(Blog blog);
    
     @Select('SELECT BLOG_ID AS blogId, BLOG_NAME as blogName, CREATED_ON as createdOn FROM BLOG WHERE BLOG_ID=#{blogId}')
     public Blog getBlogById(Integer blogId);
    
     @Select('SELECT * FROM BLOG ')
     @Results({
      @Result(id=true, property='blogId', column='BLOG_ID'),
      @Result(property='blogName', column='BLOG_NAME'),
      @Result(property='createdOn', column='CREATED_ON')  
     })
     public List<Blog> getAllBlogs();
    
     @Update('UPDATE BLOG SET BLOG_NAME=#{blogName}, CREATED_ON=#{createdOn} WHERE BLOG_ID=#{blogId}')
     public void updateBlog(Blog blog);
    
     @Delete('DELETE FROM BLOG WHERE BLOG_ID=#{blogId}')
     public void deleteBlog(Integer blogId);
    
    }
    

    Step#3: Configure BlogMapper in 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>
     <properties resource='jdbc.properties'/>
     <environments default='development'>
      <environment id='development'>
        <transactionManager type='JDBC'/>
        <dataSource type='POOLED'>
       <!-- <property name='driver' value='com.mysql.jdbc.Driver'/>
       <property name='url' value='jdbc:mysql://localhost:3306/mybatis-demo'/>
       <property name='username' value='root'/>
       <property name='password' value='admin'/> -->
       <property name='driver' value='${jdbc.driverClassName}'/>
       <property name='url' value='${jdbc.url}'/>
       <property name='username' value='${jdbc.username}'/>
       <property name='password' value='${jdbc.password}'/>
        </dataSource>
      </environment>
      </environments>
      <mappers>
        <mapper class='com.sivalabs.mybatisdemo.mappers.BlogMapper'/>
      </mappers>
    </configuration>
    

    Step#4: Create BlogService.java

    package com.sivalabs.mybatisdemo.service;
    
    import java.util.List;
    
    import org.apache.ibatis.session.SqlSession;
    
    import com.sivalabs.mybatisdemo.domain.Blog;
    import com.sivalabs.mybatisdemo.mappers.BlogMapper;
    
    public class BlogService
    {
    
     public void insertBlog(Blog blog) {
      SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
      try{
      BlogMapper blogMapper = sqlSession.getMapper(BlogMapper.class);
      blogMapper.insertBlog(blog);
      sqlSession.commit();
      }finally{
       sqlSession.close();
      }
     }
    
     public Blog getBlogById(Integer blogId) {
      SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
      try{
      BlogMapper blogMapper = sqlSession.getMapper(BlogMapper.class);
      return blogMapper.getBlogById(blogId);
      }finally{
       sqlSession.close();
      }
     }
    
     public List<Blog> getAllBlogs() {
      SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
      try{
      BlogMapper blogMapper = sqlSession.getMapper(BlogMapper.class);
      return blogMapper.getAllBlogs();
      }finally{
       sqlSession.close();
      }
     }
    
     public void updateBlog(Blog blog) {
      SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
      try{
      BlogMapper blogMapper = sqlSession.getMapper(BlogMapper.class);
      blogMapper.updateBlog(blog);
      sqlSession.commit();
      }finally{
       sqlSession.close();
      }  
     }
    
     public void deleteBlog(Integer blogId) {
      SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
      try{
      BlogMapper blogMapper = sqlSession.getMapper(BlogMapper.class);
      blogMapper.deleteBlog(blogId);
      sqlSession.commit();
      }finally{
       sqlSession.close();
      }
    
     }
    
    }
    

    Step#5: Create JUnit Test for BlogService methods

    package com.sivalabs.mybatisdemo;
    
    import java.util.Date;
    import java.util.List;
    
    import org.junit.AfterClass;
    import org.junit.Assert;
    import org.junit.BeforeClass;
    import org.junit.Test;
    
    import com.sivalabs.mybatisdemo.domain.Blog;
    import com.sivalabs.mybatisdemo.service.BlogService;
    
    public class BlogServiceTest 
    {
     private static BlogService blogService;
    
     @BeforeClass
        public static void setup() 
     {
      blogService = new BlogService();
     }
    
     @AfterClass
        public static void teardown() 
     {
      blogService = null;
     }
    
        @Test
     public void testGetBlogById() 
     {
      Blog blog = blogService.getBlogById(1);
      Assert.assertNotNull(blog);
      System.out.println(blog);
     }
    
        @Test
        public void testGetAllBlogs() 
        {
      List<Blog> blogs = blogService.getAllBlogs();
      Assert.assertNotNull(blogs);
      for (Blog blog : blogs) 
      {
       System.out.println(blog);
      }
    
     }
    
        @Test
        public void testInsertBlog() 
        {
         Blog blog = new Blog();
         blog.setBlogName('test_blog_'+System.currentTimeMillis());
         blog.setCreatedOn(new Date());
    
         blogService.insertBlog(blog);
      Assert.assertTrue(blog.getBlogId() != 0);
      Blog createdBlog = blogService.getBlogById(blog.getBlogId());
      Assert.assertNotNull(createdBlog);
      Assert.assertEquals(blog.getBlogName(), createdBlog.getBlogName());
    
     }
    
        @Test
        public void testUpdateBlog() 
        {
         long timestamp = System.currentTimeMillis();
      Blog blog = blogService.getBlogById(2);
      blog.setBlogName('TestBlogName'+timestamp);
         blogService.updateBlog(blog);
      Blog updatedBlog = blogService.getBlogById(2);
      Assert.assertEquals(blog.getBlogName(), updatedBlog.getBlogName());
     }
    
       @Test
       public void testDeleteBlog() 
       {
         Blog blog = blogService.getBlogById(4);
         blogService.deleteBlog(blog.getBlogId());
      Blog deletedBlog = blogService.getBlogById(4);
      Assert.assertNull(deletedBlog);
     }
    }
    

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