mybatis实现CRUD操作
注:数据库字段名和实体类属性名最好是一致的。如果两端不一致,造成mybatis无法填充对应的字段信息。解决方法(见后文)
数据库设计
SET FOREIGN_KEY_CHECKS=0;
-- ----------------------------
-- Table structure for user
-- ----------------------------
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(32) NOT NULL COMMENT '用户名称',
`birthday` datetime DEFAULT NULL COMMENT '生日',
`sex` char(1) DEFAULT NULL COMMENT '性别',
`address` varchar(256) DEFAULT NULL COMMENT '地址',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=57 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of user
-- ----------------------------
INSERT INTO `user` VALUES ('41', '老王', '2018-02-27 17:47:08', '男', '北京');
INSERT INTO `user` VALUES ('42', '小二王', '2018-03-02 15:09:37', '女', '北京金燕龙');
INSERT INTO `user` VALUES ('43', '小二王', '2018-03-04 11:34:34', '女', '北京金燕龙');
INSERT INTO `user` VALUES ('45', '传智播客', '2018-03-04 12:04:06', '男', '北京金燕龙');
INSERT INTO `user` VALUES ('46', '老王', '2018-03-07 17:37:26', '男', '北京');
导入依赖包
实现mybatis仅需mybatis和mysql-connect-java的包,小编这里另外导入log4j和junit是为了方便调试。
<?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>com.gohb</groupId>
<artifactId>mybatis</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<dependencies>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.4</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.12</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
</dependencies>
</project>
为log4j设置输出内容
log4j.properties
log4j.rootLogger=debug, stdout, R
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p - %m%n
log4j.appender.R=org.apache.log4j.RollingFileAppender
log4j.appender.R.File=firestorm.log
log4j.appender.R.MaxFileSize=100KB
log4j.appender.R.MaxBackupIndex=1
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n
log4j.logger.com.codefutures=DEBUG
User.java
package com.gohb.domain;
import java.io.Serializable;
import java.util.Date;
public class User implements Serializable {
private Integer id;
private String username;
private String address;
private String sex;
private Date birthday;
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", address='" + address + '\'' +
", sex='" + sex + '\'' +
", birthday=" + birthday +
'}';
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
}
QueryVo.java
package com.gohb.domain;
public class QueryVo {
private User user;
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
}
前期准备工作完成
最终目录结构如下:
MyBatis使用大致步骤总结
1)配置mybatis-config.xml 全局的配置文件 (1、数据源,2、外部的mapper)
2)创建SqlSessionFactory
3)通过SqlSessionFactory创建SqlSession对象
4)通过SqlSession操作数据库 CRUD
5)调用session.commit()提交事务
6)调用session.close()关闭会话
SqlMapConfig.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>
<!--配置环境-->
<environments default="development">
<environment id="development">
<!--配置事物-->
<transactionManager type="JDBC"></transactionManager>
<!--配置连接池-->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver" />
<property name="url" value="jdbc:mysql://localhost:3306/eesy_mybatis?useUnicode=true&characterEncoding=UTF-8" />
<property name="username" value="root" />
<property name="password" value="12345" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/gohb/dao/IUserDao.xml"/>
</mappers>
</configuration>
IUserDao.java
package com.gohb.dao;
import com.gohb.domain.QueryVo;
import com.gohb.domain.User;
import java.util.List;
public interface IUserDao {
//查询所有
List<User> findAll() throws Exception;
//保存用户
void saveUser(User user) throws Exception;
//更新用户
void updateUser(User user) throws Exception;
//根据ID删除用户
void deleteUser(Integer userId) throws Exception;
//根据ID查询用户信息
User findById(Integer userId) throws Exception;
//根据名称模糊查询用户姓名
List<User> findByName(String name)throws Exception;
//查询总记录条数
int findTotal() throws Exception;
//根据queryVo中的条件查询用户
List<User> findUserByVo(QueryVo vo)throws Exception;
}
IUserDao.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="com.gohb.dao.IUserDao">
<!--查询所有-->
<select id="findAll" resultType="com.gohb.domain.User">
select * from user
</select>
<!--保存用户-->
<insert id="saveUser" parameterType="com.gohb.domain.User">
<!--配置插入操作后,获取插入数据的id-->
<!--id:唯一标识,随便写,在同一个命名空间下保持唯一,使用动态代理之后要求和方法名保持一致
parameterType:参数的类型,使用动态代理之后和方法的参数类型一致
useGeneratedKeys:开启主键回写
keyColumn:指定数据库的主键
keyProperty:主键对应的实体类属性名-->
<selectKey keyProperty="id" keyColumn="id" resultType="int" order="AFTER">
select last_insert_id();
</selectKey>
insert into user(username,address,sex,birthday) values (#{username},#{address},#{sex},#{birthday})
</insert>
<!--更新用户-->
<update id="updateUser" parameterType="com.gohb.domain.User">
update user set username=#{username},address=#{address},sex=#{sex},birthday=#{birthday} where id=#{id}
</update>
<!--根据id删除用户-->
<delete id="deleteUser" parameterType="java.lang.Integer">
delete from user where id=#{uid}
</delete>
<!--根据id查询用户-->
<select id="findById" parameterType="INT" resultType="com.gohb.domain.User">
select * from user where id=#{id}
</select>
<!--根据姓名模糊查询-->
<select id="findByName" parameterType="String" resultType="com.gohb.domain.User">
<!--select * from user where username like '%${username}%'-->
select * from user where username like "%"#{username}"%"
</select>
<!--查询总记录条数-->
<select id="findTotal" resultType="INT">
select count(id) from user
</select>
<!--根据queryVo的条件查询用户-->
<select id="findUserByVo" parameterType="com.gohb.domain.QueryVo" resultType="com.gohb.domain.User">
select * from user where username like "%"#{user.username}"%"
</select>
</mapper>
测试类编写
package com.gohb;
import com.gohb.dao.IUserDao;
import com.gohb.domain.QueryVo;
import com.gohb.domain.User;
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.After;
import org.junit.Before;
import org.junit.Test;
import java.io.InputStream;
import java.util.Date;
import java.util.List;
public class test {
private InputStream in;
private SqlSession sqlSession;
private IUserDao userDao;
@Before
public void init()throws Exception{
in = Resources.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
SqlSessionFactory factory = builder.build(in);
sqlSession = factory.openSession();
userDao = sqlSession.getMapper(IUserDao.class);
}
@After
public void destory()throws Exception{
sqlSession.close();
in.close();
}
/**
* 测试查询所有
*/
@Test
public void testFindAll() throws Exception{
List<User> users = userDao.findAll();
for (User user :
users) {
System.out.println(user);
}
}
/**
* 测试保存操作
*/
@Test
public void testSave() throws Exception{
User user = new User();
user.setId(41);
user.setUsername("gohb");
user.setAddress("北京");
user.setSex("男");
user.setBirthday(new Date());
userDao.saveUser(user);
sqlSession.commit();
System.out.println(user);
}
/**
* 更新用户
*/
@Test
public void testUpdate() throws Exception{
User user = new User();
user.setId(51);
user.setUsername("gohbupdate");
user.setAddress("北京");
user.setSex("女");
user.setBirthday(new Date());
userDao.updateUser(user);
sqlSession.commit();
}
/**
* 根据id删除
*/
@Test
public void testDelete()throws Exception{
userDao.deleteUser(48);
sqlSession.commit();
}
/**
* 根据id查询
*/
@Test
public void testFindOne()throws Exception{
User user = userDao.findById(46);
sqlSession.commit();
System.out.println(user);
}
/**
* 根据姓名模糊查询
*/
@Test
public void testFindByName()throws Exception{
List<User> users = userDao.findByName("gohb");
for (User user:
users) {
System.out.println(user);
}
sqlSession.commit();
}
/**
* 查询总记录条数
*/
@Test
public void testFindTotal()throws Exception{
int total = userDao.findTotal();
System.out.println(total);
}
/**
* 根据QueryVo作为查询条件
*/
@Test
public void testFindByQueryVo()throws Exception{
QueryVo vo = new QueryVo();
User user = new User();
user.setUsername("gohb");
vo.setUser(user);
List<User> users = userDao.findUserByVo(vo);
for (User u:
users) {
System.out.println(u);
}
sqlSession.commit();
}
}
- SqlSessionFactoryBuilder创建工厂使用了构建者模式,把对象的创建细节隐藏,使使用者直接调用方法即可拿到对象。
- factory.openSession()生成sqlSession使用了工厂模式。优势:解耦(降低类之间的依赖关系)
- sqlSession.getMapper(IUserDao.class)创建Dao接口实现类使用代理模式。优势:不修改源码的基础上对已有方法进行增强
关于数据库字段名和实体类属性名不一致的解决方法
假设实体类User的属性如下:
1.在sql语句中使用别名
2.利用mybatis本身,配置查询结果列名和实体类属性的对应关系
<!--配置查询结果列名和实体类属性的对应关系-->
<!--id:唯一标识,随便写-->
<resultMap id="userMap" type="com.gohb.domain.User">
<!--主键字段的对应-->
<!--property:主键对应的实体类属性
column:指定数据库的主键-->
<id property="userId" column="id"></id>
<!--非主键字段的对应-->
<result property="userName" column="username"></result>
<result property="userAddress" column="address"></result>
<result property="userSex" column="sex"></result>
<result property="userBirthday" column="birthday"></result>
</resultMap>
<!--查询所有-->
<select id="findAll" resultMap="userMap">
select * from user
</select>