1.实体类User.java
public class User {
private int id;
private String name;
private int age;
//getter、setter...
}
2.接口类UserMapper.java
public interface UserMapper {
//添加
@Insert("insert into users (name,age) values (#{name},#{age})")
public int addUser(User user) throws Exception;
//删除
@Delete("delete from users where id = #{id}")
public void deleteUser(int id) throws Exception;
//修改
@Update("update users set name=#{name},age=#{age} where id=#{id}")
public void updateUser(User user) throws Exception;
//查询
@Select("select * from users where id = #{id}")
public User queryUser(int id) throws Exception;
//查询所有的用户
@Select("select * from users")
public List<User> queryAllUser() throws Exception;
}
3.全局配置文件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>
<!-- 映入外部配置文件 -->
<properties resource="mysql.properties"></properties>
<!-- 配置mybatis运行环境,development:开发模式,work:工作模式-->
<environments default="development">
<environment id="development">
<!-- type=“jdbc”表示使用JDBC的提交和回滚来管理事务 -->
<transactionManager type="JDBC" />
<!-- mybatis提供了三种数据源类型,POOLED,UNPOOLED,JNDI -->
<!-- POOLED:表示支持JDBC数据源的连接池 -->
<!-- UNPOOLED:表示不支持JDBC数据源的连接池 -->
<!-- JNDI:表示支持外部数据源连接池 -->
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}" />
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
</dataSource>
</environment>
</environments>
<mappers>
<!-- 基于注解的增删改查,注册接口,注意Mapper标签的属性为class,引入xml文件是resource -->
<mapper class="com.test.withAnno.UserMapper"/>
</mappers>
<!-- 为实体类定义别名,简化sql映射xml文件中的引用 -->
<!-- <typeAliases>
<typeAlias type="com.test.bean.User" alias="_User"/>
</typeAliases> -->
</configuration>
4.数据库配置文件mysql.properties
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis1?useUincode=true&characterEncoding=UTF-8
jdbc.username=root
jdbc.password=root
5.测试类
/**
* @author:滕鹏飞
* @version: 1.0
* @Created on: 2018-9-2 下午9:05:14
* 类说明
*/
public class Test {
public static void main(String[] args) {
addUser();
//deleteUser();
//updateUser();
//queryUser();
//queryAllUser();
}
//添加
public static void addUser() {
SqlSession session = DBUtil.getSession();
UserMapper mapper = session.getMapper(UserMapper.class);
User u = new User("张三",21);
try {
mapper.addUser(u);
session.commit();
System.out.println(u.toString());
} catch (Exception e) {
e.printStackTrace();
session.rollback();
}finally{
session.close();
}
}
//删除
public static void deleteUser() {
SqlSession session = DBUtil.getSession();
UserMapper mapper = session.getMapper(UserMapper.class);
try {
mapper.deleteUser(2);
session.commit();
} catch (Exception e) {
e.printStackTrace();
session.rollback();
}finally{
session.close();
}
}
//修改
public static void updateUser() {
SqlSession session = DBUtil.getSession();
UserMapper mapper = session.getMapper(UserMapper.class);
try {
User user = new User(3,"Tom",24);
mapper.updateUser(user);
session.commit();
} catch (Exception e) {
e.printStackTrace();
session.rollback();
}finally{
session.close();
}
}
//查询
public static void queryUser() {
SqlSession session = DBUtil.getSession();
UserMapper mapper = session.getMapper(UserMapper.class);
try {
User user = mapper.queryUser(4);
session.commit();
System.out.println(user.toString());
} catch (Exception e) {
e.printStackTrace();
session.rollback();
}finally{
session.close();
}
}
//查询所有
public static void queryAllUser() {
SqlSession session = DBUtil.getSession();
UserMapper mapper = session.getMapper(UserMapper.class);
try {
List<User> users = mapper.queryAllUser();
session.commit();
System.out.println(users);
} catch (Exception e) {
e.printStackTrace();
session.rollback();
}finally{
session.close();
}
}
}
6.注意:
注解和XML文件的差别不大,注意配置文件中引入是的属性
异常问题
1.Caused by: org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 1; 前言中不允许有内容。
原因:为mybatis.cfg.xml里注册UserMapper.xml文件时,路径错误
2.Cause: org.xml.sax.SAXParseException; lineNumber: 27; columnNumber: 40; 需要属性 "name", 并且必须为元素类型 "package" 指定该属性。
原因:在配置文件中引入映射文件,忘记将接口类引入到配置文件中,所以新手的话需要按照教程一步一来
3.Caused by: org.xml.sax.SAXParseException; lineNumber: 29; columnNumber: 13; 与元素类型 "id" 相关联的属性 "{1}" 应有左引号。
原因:映射文件29行少一个左引号
4.Type interface com.test.mapper.UserMapper is already known to the MapperRegistry.
原因:在映射文件的节点<mapper>中配置了的namespace,同时在配置文件中又引入了这个接口