案例背景:
数据库表中一个订单对应着一个用户信息
根据一个订单ID只可以查询出一条用户记录
我们需要查询出所有的订单信息并且信息中包含有对应的用户记录
补充:
同以往Order的定义不同,Order中需要封装User属性
一.案例展示
1.测试准备
①数据库mysql一枚
②database名为batistest且表名为user和order
③项目工程
2.代码展示(着重关注OrderMapper.xml的配置)
***pom.xml
<?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.howie</groupId>
<artifactId>mybatis_manual_mapping_one2one</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
<dependencies>
<!--单元测试-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<!--mysql驱动-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.46</version>
</dependency>
<!--mybatis-->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.5</version>
</dependency>
<!--log4j-->
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
</dependencies>
</project>
***bean.properties
OrderService=com.howie.service.impl.OrderServiceImpl
***db.properties
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/batistest?characterEncoding=utf-8
jdbc.username=root
jdbc.password=root
***log4j.properties
#log4j日志级别如下:
#A:off 最高等级,用于关闭所有日志记录。
#B:fatal 指出每个严重的错误事件将会导致应用程序的退出。
#C:error 指出虽然发生错误事件,但仍然不影响系统的继续运行。
#D:warn 表明会出现潜在的错误情形。
#E:info 一般和在粗粒度级别上,强调应用程序的运行全程。
#F:debug 一般用于细粒度级别上,对调试应用程序非常有帮助。
#G:all 最低等级,用于打开所有日志记录。
#但log4j只建议使用4个级别,优先级从高到低分别是:
#error>warn>info>debug
log4j.rootLogger=debug,systemOut,logFile
#输出到控制台
log4j.appender.systemOut=org.apache.log4j.ConsoleAppender
log4j.appender.systemOut.layout=org.apache.log4j.PatternLayout
log4j.appender.systemOut.layout.ConversionPattern=[%-5p][%-22d{yyyy/MM/dd HH:mm:ssS}][%l]%n%m%n
log4j.appender.systemOut.Target=System.out
#输出到文件
log4j.appender.logFile=org.apache.log4j.FileAppender
log4j.appender.logFile.layout=org.apache.log4j.PatternLayout
log4j.appender.logFile.layout.ConversionPattern=[%-5p][%-22d{yyyy/MM/dd HH:mm:ssS}][%l]%n%m%n
log4j.appender.logFile.File=E:/log/log4j.log
log4j.appender.logFile.Encoding=UTF-8
#将日志输记录到MySQL数据库
#log4j.appender.logDB = org.apache.log4j.jdbc.JDBCAppender
#log4j.appender.logDB.layout = org.apache.log4j.PatternLayout
#log4j.appender.logDB.Driver = com.mysql.jdbc.Driver
#log4j.appender.logDB.URL = jdbc:mysql://localhost:3306/log4j?characterEncoding=utf-8
#log4j.appender.logDB.User = root
#log4j.appender.logDB.Password = root
#log4j.appender.logDB.Sql = INSERT INTO t_log4j(project_name,create_date,level,category,file_name,thread_name,line,all_category,message)values('mybatis','%d{yyyy-MM-ddHH:mm:ss}','%p','%c','%F','%t','%L','%l','%m')
#若出现问题:Log4j: ERROR Failed to load driver, java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
#解决方法:将log4j.properties 中每行后面的空格都删除就解决了.
***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>
<!--
从外部文件db.properties读取数据库连接信息
-->
<properties resource="db.properties"/>
<!--配置log4j日志-->
<settings>
<setting name="logImpl" value="LOG4J"/>
</settings>
<!--批量起别名-->
<typeAliases>
<package name="com.howie.pojo"/>
</typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<!--获取db文件中的数据-->
<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>
<!--批量扫描mapper-->
<mappers>
<!--<mapper resource="XxxMapper.xml"/>-->
<package name="com.howie.mapper"/>
</mappers>
</configuration>
***BeanFactory.java
package com.howie.utils;
import org.apache.ibatis.session.SqlSession;
import java.lang.reflect.Constructor;
import java.util.ResourceBundle;
/**
* Bean工厂对象
* 方法:
* 传递接口,传递的是接口的class文件对象
* 返回实现类的对象
*
* 泛型: 本身没有类型,未知的数据类型
* 调用的时候,传递什么,就是什么类型
*/
public class BeanFactory {
public static <T>T newInstance(Class<T> clazz){
//获取传递的接口名
String name = clazz.getSimpleName();
//读取配置文件
ResourceBundle resourceBundle = ResourceBundle.getBundle("bean");
String className = resourceBundle.getString(name);
//反射创建对象
try {
return (T)Class.forName(className).newInstance();
}catch (Exception ex){
ex.printStackTrace();
}
return null;
}
/**
* 带参构造
* @param clazz
* @param sqlSession
* @param <T>
* @return
*/
public static <T>T newInstance(Class<T> clazz, SqlSession sqlSession){
//获取传递的接口名
String name = clazz.getSimpleName();
//读取配置文件
ResourceBundle resourceBundle = ResourceBundle.getBundle("bean");
String className = resourceBundle.getString(name);
//获取带参构造函数
try {
Constructor constructor = Class.forName(className).getConstructor(SqlSession.class);
Object[] params = {sqlSession};
//反射创建对象
return (T)constructor.newInstance(params);
}catch (Exception ex){
ex.printStackTrace();
}
return null;
}
}
***Order.java
package com.howie.pojo;
import java.util.Date;
/**
* @Author weihuanwen
* @Date 2019/8/12 11:23
* @Version 1.0
*/
public class Order {
private int id;
private int userId;
private String number;
private Date createtime;
private String note;
private User user;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getUserId() {
return userId;
}
public void setUserId(int userId) {
this.userId = userId;
}
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
public Date getCreatetime() {
return createtime;
}
public void setCreatetime(Date createtime) {
this.createtime = createtime;
}
public String getNote() {
return note;
}
public void setNote(String note) {
this.note = note;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
@Override
public String toString() {
return "Order{" +
"id=" + id +
", userId=" + userId +
", number='" + number + '\'' +
", createtime=" + createtime +
", note='" + note + '\'' +
", user=" + user +
'}';
}
}
***User.java
package com.howie.pojo;
import com.sun.org.apache.xpath.internal.operations.Or;
import java.util.Date;
import java.util.List;
/**
* @Author weihuanwen
* @Date 2019/8/9 9:54
* @Version 1.0
*/
public class User {
private Integer id;
private String username;
private Integer sex;
private Date birthday;
private String address;
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 Integer getSex() {
return sex;
}
public void setSex(Integer sex) {
this.sex = sex;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", sex=" + sex +
", birthday=" + birthday +
", address='" + address + '\'' +
'}';
}
}
***OrderMapper.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.howie.mapper.OrderMapper">
<!--是否开启二级缓存(开启,则打开注释)-->
<!--<cache/>-->
<!--查询所有订单-->
<select id="queryOrders" resultMap="orderResultMap">
SELECT
o.`id`,
o.`user_id` userId,
o.`number`,
o.`createtime`,
o.`note`,
u.`id` uid,
u.`username`,
u.`address`
FROM
`order` o
LEFT JOIN `user` u ON o.`user_id` = u.`id`
</select>
<!--手动映射-->
<resultMap id="orderResultMap" type="Order">
<!--基本属性封装-->
<id column="id" property="id"/>
<id column="userId" property="userId"/>
<id column="number" property="number"/>
<id column="createtime" property="createtime"/>
<id column="note" property="note"/>
<!--完成一对一中user属性封装-->
<association property="user" javaType="user">
<id column="uid" property="id"/>
<result column="username" property="username"/>
<result column="address" property="address"/>
</association>
</resultMap>
</mapper>
***OrderMapper.java
package com.howie.mapper;
import com.howie.pojo.Order;
import java.util.List;
/**
* @Author weihuanwen
* @Date 2019/8/12 11:24
* @Version 1.0
*/
public interface OrderMapper {
/**
* 查询所有的订单
* @return
*/
List<Order> queryOrders();
}
***OrderService.java
package com.howie.service;
import com.howie.pojo.Order;
import java.util.List;
/**
* @Author weihuanwen
* @Date 2019/8/12 11:34
* @Version 1.0
*/
public interface OrderService {
/**
* 查询所有的订单
* @return
*/
List<Order> queryOrders();
}
***OrderServiceImpl.java
package com.howie.service.impl;
import com.howie.mapper.OrderMapper;
import com.howie.pojo.Order;
import com.howie.service.OrderService;
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;
import java.util.List;
/**
* @Author weihuanwen
* @Date 2019/8/12 11:35
* @Version 1.0
*/
public class OrderServiceImpl implements OrderService {
private static SqlSession sqlSession;
private static OrderMapper orderMapperImpl;
static {
try {
SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();
//加载SqlMapConfig.xml文件
InputStream is = Resources.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactory ssf = ssfb.build(is);
sqlSession = ssf.openSession();
orderMapperImpl = sqlSession.getMapper(OrderMapper.class);
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 查询所有的订单信息
* @return
*/
@Override
public List<Order> queryOrders() {
return orderMapperImpl.queryOrders();
}
}
***OrderController.java
package com.howie.controller;
import com.howie.pojo.Order;
import com.howie.service.OrderService;
import com.howie.utils.BeanFactory;
import org.junit.Test;
import java.util.List;
/**
* @Author weihuanwen
* @Date 2019/8/12 11:41
* @Version 1.0
*/
public class OrderController {
private OrderService orderService = BeanFactory.newInstance(OrderService.class);
@Test
public void queryOrders(){
List<Order> orders = orderService.queryOrders();
orders.forEach(System.out::println);
}
}
3.测试
执行queryOrders()后控制台输出
Order{id=1, userId=3, number='1000010', createtime=Wed Feb 04 13:22:35 CST 2015, note='质量很好', user=User{id=3, username='王五', sex=null, birthday=null, address='广州'}}
Order{id=2, userId=3, number='1000011', createtime=Tue Feb 03 13:22:41 CST 2015, note='非常漂亮', user=User{id=3, username='王五', sex=null, birthday=null, address='广州'}}
Order{id=3, userId=4, number='1000012', createtime=Thu Feb 12 16:13:23 CST 2015, note='物超所值', user=User{id=4, username='赵六', sex=null, birthday=null, address='深圳'}}