前言
本文介绍如何在java中使用mybatis，本文使用maven项目。
准备数据库
create table `Blog`(
`id` INT(11) NOT NULL AUTO_INCREMENT,
`name` CHAR(20) DEFAULT '' COMMENT '名字',
PRIMARY KEY(`id`)
)COMMENT="博客";
INSERT INTO Blog (id,name) VALUES (101,'nick');
INSERT INTO Blog (name) VALUES ('nickqiu');
编码
- 新建maven项目org.nick.mybatistest，加入依赖
<?xml version="1.0" encoding="UTF-8"?>
<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>org.nick</groupId>
<artifactId>mybatis-demo</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.6</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.16.20</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.46</version>
</dependency>
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.4</version>
</dependency>
</dependencies>
</project>
- mybatis 配置 mybatisdemo/src/main/resources/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>
<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/test"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
<!--<property name="url" value="${url}"/>-->
<!--<property name="username" value="${username}"/>-->
<!--<property name="password" value="${password}"/>-->
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="sqlmapping/BlogMapper.xml"/>
</mappers>
</configuration>
- 类配置文件mybatisdemo/src/main/resources/sqlmapping/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="org.nick.mybatistest.BlogMapper">
<select id="selectBlog" resultType="org.nick.mybatistest.entity.Blog">
select * from Blog where id = #{id}
</select>
</mapper>
- 实体类mybatisdemo/src/main/java/org/nick/mybatistest/entity/Blog.java
package org.nick.mybatistest.entity;
import lombok.Data;
@Data
public class Blog {
private int id;
private String name;
}
- 数据库链接类mybatisdemo/src/main/java/org/nick/mybatistest/dao/DbConnect.java
package org.nick.mybatistest.dao;
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 java.io.IOException;
import java.io.InputStream;
/**
* 链接数据库
*/
public class DbConnect {
private static SqlSessionFactory sqlSessionFactory = null;
private static String resource = "mybatis-config.xml";
private static synchronized void get(){
if(sqlSessionFactory == null){
InputStream inputStream = null;
try {
inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (
IOException e) {
e.printStackTrace();
}
}
}
public static SqlSession getSqlSection(){
get();
SqlSession session = sqlSessionFactory.openSession();
return session;
}
}
- 测试类
package org.nick.mybatistest;
import com.google.gson.Gson;
import org.apache.ibatis.session.SqlSession;
import org.nick.mybatistest.dao.DbConnect;
import org.nick.mybatistest.entity.Blog;
public class Application {
public static void main(String[] args) {
SqlSession session = DbConnect.getSqlSection();
try {
Blog blog = (Blog) session.selectOne("org.nick.mybatistest.BlogMapper.selectBlog", 101);
System.out.println("blog:"+new Gson().toJson(blog));
} finally {
session.close();
}
}
}
执行效果
image.png
改造使用接口
- 添加接口mapper类
package org.nick.mybatistest.dao;
import org.apache.ibatis.annotations.Select;
import org.nick.mybatistest.entity.Blog;
public interface BlogMapper1 {
@Select("SELECT * FROM blog WHERE id = #{id}")
Blog selectBlog(int id);
}
- 修改DB链接类的get方法，java代码中添加mapper
package org.nick.mybatistest.dao;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;
/**
* 链接数据库
*/
public class DbConnect {
private static SqlSessionFactory sqlSessionFactory = null;
private static String resource = "mybatis-config.xml";
private static synchronized void get(){
if(sqlSessionFactory == null){
InputStream inputStream = null;
try {
inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
Configuration configuration = sqlSessionFactory.getConfiguration();
configuration.addMapper(BlogMapper1.class);
} catch (
IOException e) {
e.printStackTrace();
}
}
}
public static SqlSession getSqlSection(){
get();
SqlSession session = sqlSessionFactory.openSession();
return session;
}
}
- 新的测试类
package org.nick.mybatistest;
import com.google.gson.Gson;
import org.apache.ibatis.session.SqlSession;
import org.nick.mybatistest.dao.BlogMapper1;
import org.nick.mybatistest.dao.DbConnect;
import org.nick.mybatistest.entity.Blog;
public class Application1 {
public static void main(String[] args) {
SqlSession session = DbConnect.getSqlSection();
try {
BlogMapper1 mapper = session.getMapper(BlogMapper1.class);
Blog blog = mapper.selectBlog(101);
System.out.println("blog:"+new Gson().toJson(blog));
} finally {
session.close();
}
}
}
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