17.Mybatis的基本使用及入门案例
一、什么是 MyBatis ？
MyBatis 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。
二、入门案例
maven工程样式
创建maven工程，添加对应jar包（在pom.xml文件中插入）
<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.sxt</groupId> <artifactId>mybatis.01.hello</artifactId> <version>0.0.1-SNAPSHOT</version> <dependencies> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.4.6</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.32</version> </dependency> </dependencies> </project>
创建全局配置文件，该配置文件包含了对 MyBatis 系统的核心设置，包含获取数据库连接实例的数据源（DataSource）和决定事务作用域和控制方式的事务管理器TransactionManager）。（文件命名为mybatis-cfg.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/j0325?characterEncoding=utf-8"/> <property name="username" value="root"/> <property name="password" value="123"/> </dataSource> </environment> </environments> <mappers> <!-- 关联映射文件 --> <mapper resource="com/sxt/pojo/UserMapper.xml"/> </mappers> </configuration>
定义User对象
package com.sxt.pojo;
public class User {
private Integer id;
private String name;
private Integer age;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "User [id=" + id + ", name=" + name + ", age=" + age + "]";
}
}
创建映射文件（文件命名为UserMapper.xml），并将映射文件添加到主配置文件中
<?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"> <!-- namespace 名称空间：作用是用来区分各个xml映射文件 --> <mapper namespace="com.sxt.pojo.User"> <select id="query" resultType="com.sxt.pojo.User"> select * from t_user </select> <insert id="addUser" parameterType="com.sxt.pojo.User"> insert into t_user(name,age)values(#{name},#{age}) </insert> <delete id="deleteById" parameterType="int"> delete from t_user where id=#{id} </delete> <update id="updateUser" parameterType="com.sxt.pojo.User"> update t_user set name=#{name} , age=#{age} where id=#{id} </update> <select id="queryById" resultType="com.sxt.pojo.User"> select * from t_user where id = #{id} </select> </mapper>
测试
package com.sxt.test; import java.io.IOException; 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.Test; import com.sxt.pojo.User; public class MybatisTest01 { @Test public void query() throws IOException { InputStream in = Resources.getResourceAsStream("mybatis-cfg.xml"); SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in); SqlSession session = factory.openSession(); List<User> list = session.selectList("com.sxt.pojo.User.query"); for (User user : list) { System.out.println(user); } session.close(); } @Test public void queryById() throws IOException { InputStream in = Resources.getResourceAsStream("mybatis-cfg.xml"); SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in); SqlSession session = factory.openSession(); List<User> list = session.selectList("com.sxt.pojo.User.queryById", 1); for (User user : list) { System.out.println(user); } session.close(); } @Test public void addUser() throws IOException { InputStream in = Resources.getResourceAsStream("mybatis-cfg.xml"); SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in); SqlSession session = factory.openSession(); User user = new User(); user.setName("wdh"); user.setAge(18); int count = session.insert("com.sxt.pojo.User.addUser", user); session.commit(); System.out.println("影响的行数：" + count); session.close(); } @Test public void updateUser()throws IOException{ InputStream in = Resources.getResourceAsStream("mybatis-cfg.xml"); SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in); SqlSession session = factory.openSession(); User user = new User(); user.setId(1); user.setName("cc"); user.setAge(27); int count = session.insert("com.sxt.pojo.User.updateUser", user); session.commit(); System.out.println("受影响的行数:"+count); session.close(); } @Test public void deleteUser()throws IOException{ InputStream in = Resources.getResourceAsStream("mybatis-cfg.xml"); SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in); SqlSession session = factory.openSession(); int count = session.insert("com.sxt.pojo.User.deleteById",1); session.commit(); System.out.println("受影响的行数:"+count); session.close(); } }
