MyBatis教程– CRUD操作和映射关系–第1部分

CRUD操作
MyBatis是一个SQL Mapper工具，与直接使用JDBC相比，它极大地简化了数据库编程。

步骤1：创建一个Maven项目并配置MyBatis依赖项。 

<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>

步骤2：创建表USER和Java域对象User，如下所示： 

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;@Overridepublic String toString() {return 'User [userId=' + userId + ', emailId=' + emailId+ ', password=' + password + ', firstName=' + firstName+ ', lastName=' + lastName + ']';}//setters and getters 
}

步骤＃3：创建MyBatis配置文件。

a）在src / main / resources文件夹中创建jdbc.properties文件 

jdbc.driverClassName=com.mysql.jdbc.Driverjdbc.url=jdbc:mysql://localhost:3306/mybatis-demojdbc.username=rootjdbc.password=admin

b）在src / main / resources文件夹中创建mybatis-config.xml文件 

<?xml version='1.0' encoding='UTF-8' ?><!DOCTYPE configurationPUBLIC '-//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>

步骤＃4：在com.sivalabs.mybatisdemo.mappers包的src / main / java文件夹中创建一个UserMapper.java接口。 

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);}

步骤5：在com.sivalabs.mybatisdemo.mappers包的src / main / resources文件夹中创建UserMapper.xml文件。 

<?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 lastNameFROM 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 SETPASSWORD= #{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>

步骤＃6：创建MyBatisUtil.java实例化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;}
}

步骤＃7：在src / main / java文件夹中创建UserService.java。 

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();}}}

步骤＃8：创建一个JUnit Test类来测试UserService方法。 

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;@BeforeClasspublic static void setup() {userService = new UserService();}@AfterClasspublic static void teardown() {userService = null;}@Testpublic void testGetUserById() {User user = userService.getUserById(1);Assert.assertNotNull(user);System.out.println(user);}@Testpublic void testGetAllUsers() {List<User> users = userService.getAllUsers();Assert.assertNotNull(users);for (User user : users) {System.out.println(user);}}@Testpublic 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());}@Testpublic 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());}@Testpublic void testDeleteUser() {User user = userService.getUserById(4);userService.deleteUser(user.getUserId());User deletedUser = userService.getUserById(4);Assert.assertNull(deletedUser);   }
}

现在，我将解释如何使用MyBatis注释支持执行CRUD操作，而无需在XML映射器文件中进行查询配置。

步骤＃1 ：创建一个表BLOG和一个Java域对象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;@Overridepublic String toString() {return 'Blog [blogId=' + blogId + ', blogName=' + blogName+ ', createdOn=' + createdOn + ']';}//Seeters and getters
}

步骤2 ：在Annotations中使用SQL查询创建UserMapper.java接口。 

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);}

步骤＃3 ：在mybatis-config.xml中配置BlogMapper 

<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE configurationPUBLIC '-//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>

步骤＃4 ：创建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();}}}

步骤＃5 ：为BlogService方法创建JUnit测试 

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;@BeforeClasspublic static void setup() {blogService = new BlogService();}@AfterClasspublic static void teardown() {blogService = null;}@Testpublic void testGetBlogById() {Blog blog = blogService.getBlogById(1);Assert.assertNotNull(blog);System.out.println(blog);}@Testpublic void testGetAllBlogs() {List<Blog> blogs = blogService.getAllBlogs();Assert.assertNotNull(blogs);for (Blog blog : blogs) {System.out.println(blog);}}@Testpublic 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());}@Testpublic 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());}@Testpublic void testDeleteBlog() {Blog blog = blogService.getBlogById(4);blogService.deleteBlog(blog.getBlogId());Blog deletedBlog = blogService.getBlogById(4);Assert.assertNull(deletedBlog);}
}

参考： MyBatis教程：第1部分–来自JCG合作伙伴 Siva Reddy的“ CRUD操作”，位于“我的技术实验”博客上。

翻译自: https://www.javacodegeeks.com/2012/11/mybatis-tutorial-crud-operations-and-mapping-relationships-part-1.html

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