1,聲明
本部落格所有内容來源于網絡、書籍、和各類手冊。
内容均為非盈利,旨為學習記錄,友善查詢、總結備份、開源分享。
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參考連結
[Mybatis(三) 映射檔案詳解(https://www.cnblogs.com/whgk/p/6718979.html)
2, 工具
Idea 2019.2
maven 3.61
mysql 8.017
mybatis
3,依賴jar包 Dependencies
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.7</maven.compiler.source>
<maven.compiler.target>1.7</maven.compiler.target>
<!-- spring版本号 -->
<spring.version>5.1.9.RELEASE</spring.version>
<!-- Mybatis版本号 -->
<mybatis.version>3.4.6</mybatis.version>
<!-- log4j 版本号 -->
<log4j.version>1.2.17</log4j.version>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<!-- spring核心包 -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-oxm</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-tx</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context-support</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-test</artifactId>
<version>${spring.version}</version>
</dependency>
<!-- 導入dbcp的jar包,用來在applicationContext.xml中配置資料庫 -->
<dependency>
<groupId>commons-dbcp</groupId>
<artifactId>commons-dbcp</artifactId>
<version>1.4</version>
</dependency>
<!-- mybatis核心包 -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>${mybatis.version}</version>
</dependency>
<!-- mybatis/spring包 -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis-spring</artifactId>
<version>1.3.2</version>
</dependency>
<!-- 導入Mysql資料庫連結jar包 -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.16</version>
</dependency>
<!-- 日志檔案管理包 -->
<!-- log start -->
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>${log4j.version}</version>
</dependency>
</dependencies>
<build>
<pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
<plugins>
<!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
<plugin>
<artifactId>maven-clean-plugin</artifactId>
<version>3.1.0</version>
</plugin>
<!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
<plugin>
<artifactId>maven-resources-plugin</artifactId>
<version>3.0.2</version>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
</plugin>
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.22.1</version>
</plugin>
<plugin>
<artifactId>maven-jar-plugin</artifactId>
<version>3.0.2</version>
</plugin>
<plugin>
<artifactId>maven-install-plugin</artifactId>
<version>2.5.2</version>
</plugin>
<plugin>
<artifactId>maven-deploy-plugin</artifactId>
<version>2.8.2</version>
</plugin>
<!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
<plugin>
<artifactId>maven-site-plugin</artifactId>
<version>3.7.1</version>
</plugin>
<plugin>
<artifactId>maven-project-info-reports-plugin</artifactId>
<version>3.0.0</version>
</plugin>
</plugins>
</pluginManagement>
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.xml</include>
</includes>
</resource>
</resources>
</build>
</project>
4,代碼結構
![](https://img.laitimes.com/img/__Qf2AjLwojIjJCLyojI0JCLiAzNfRHLGZkRGZkRfJ3bs92YsYTMfVmepNHL6dGVOVzaE1UMNpHW4Z0MMBjVtJWd0ckW65UbM5WOHJWa5kHT20ESjBjUIF2X0hXZ0xCMx81dvRWYoNHLrdEZwZ1Rh5WNXp1bwNjW1ZUba9VZwlHdssmch1mclRXY39CXldWYtlWPzNXZj9mcw1ycz9WL49zZuBnLwcTOyITMwgTMzETMxkTMwIzLc52YucWbp5GZzNmLn9Gbi1yZtl2Lc9CX6MHc0RHaiojIsJye.png)
5, Mybatis Generator 配置檔案
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>
<!-- 取别名,或者别的其他全局配置資訊,就在這裡編寫 -->
<typeAliases>
<!-- 别名為類名首字母大小寫都可以 -->
<package name="com.hardes.pojos"/>
</typeAliases>
<!-- 原先這裡還有連接配接資料庫的一些配置,與spring整合後,都交由spring來管理 -->
<!-- 加載mapper映射檔案,使用通用的配置 -->
<mappers>
<package name="com.hardes.mappers"/>
</mappers>
</configuration>
6, Spring 配置檔案
applicationContext.xml
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx.xsd ">
<!-- 引用java配置檔案 -->
<context:property-placeholder location="classpath:jdbc.properties"/>
<!-- 配置資料源 -->
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
<property name="driverClassName" value="${db.driver}"/>
<property name="url" value="${db.url}"/>
<property name="username" value="${db.username}"/>
<property name="password" value="${db.password}"/>
<property name="maxActive" value="10"/>
<property name="maxIdle" value="5"/>
</bean>
<!-- 配置SqlSessionFactory -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<!-- 指定mybatis的全局配置檔案的路徑 -->
<property name="configLocation" value="classpath:mybatis/SqlMapConfig.xml"></property>
<!-- 資料源 -->
<property name="dataSource" ref="dataSource"></property>
</bean>
<!-- 批量配置,這裡是批量配置mapper代理,那麼下面就不用配置id了。
我們想要擷取哪個mapper代理用這個格式:類名首字母小寫
-->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.hardes.mappers"></property>
<!-- 預設不需要配置,但是如果有多個資料源的配置,那麼就需要配置此項 -->
<property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"></property>
</bean>
</beans>
jdbc.properties
db.driver=com.mysql.cj.jdbc.Driver
db.url=jdbc:mysql:///test?characterEncoding=utf8&useUnicode=true&useSSL=false&serverTimezone=UTC
db.username=root
db.password=root
mappers
OrdersMapper.java
package com.hardes.mappers;
import com.hardes.pojos.OrdersExt;
import java.util.List;
public interface OrdersMapper {
List<OrdersExt> findOrdersAndUsersByOid(int i);
}
OrdersMapper.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">
<!--
namespace命名空間,作用就是對sql進行分類化管理,将sql隔離
注意:使用mapper代理方法開發,namespace有特殊重要的作用,namespace為對應的mapper接口位址
-->
<mapper namespace="com.hardes.mappers.OrdersMapper">
<!--一對一映射,還用resultType-->
<select id="findOrdersAndUsersByOid" parameterType="int" resultType="com.hardes.pojos.OrdersExt">
SELECT *
FROM users,orders WHERE orders.id=#{oid} AND orders.user_id= users.id
</select>
</mapper>
UsersMapper.java
package com.hardes.mappers;
import com.hardes.pojos.Users;
import java.util.List;
public interface UsersMapper {
List<Users> findOrdersAndUsersByOid1(int id);
}
UsersMapper.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">
<!--
namespace命名空間,作用就是對sql進行分類化管理,将sql隔離
注意:使用mapper代理方法開發,namespace有特殊重要的作用,namespace為對應的mapper接口位址
-->
<mapper namespace="com.hardes.mappers.UsersMapper">
<resultMap id="findOrdersAndUsersReM" type="com.hardes.pojos.Users">
<id column="uid" property="id"/>
<result column="username" property="username"/>
<result column="sex" property="sex"/>
<association property="orders" javaType="com.hardes.pojos.Orders">
<id column="oid" property="id"/>
<result column="number" property="number"/>
<result column="user_id" property="userId"/>
<result column="time" property="time"/>
</association>
</resultMap>
<select id="findOrdersAndUsersByOid1" parameterType="int" resultMap="findOrdersAndUsersReM">
SELECT
users.id uid,
users.username,
users.sex,
orders.id oid,
orders.number,
orders.user_id,
orders.time
FROM users,orders WHERE users.id=#{id} AND users.id=orders.user_id
</select>
</mapper>
7, pojos(Items 和detail_list類沒有涉及,沒有放)
Users.java
package com.hardes.pojos;
import java.util.Date;
import java.util.List;
public class Users {
private int id;
private String username;
private String sex;
private Date birthday;
private String address;
//private Orders orders;
//訂單資訊集合
// private List<Orders> ordersList;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
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;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "Users{" +
"id=" + id +
", username='" + username + '\'' +
", sex='" + sex + '\'' +
", birthday=" + birthday +
", address='" + address + '\'' +
'}';
}
}
Orders.java
package com.hardes.pojos;
import java.util.Date;
import java.util.List;
public class Orders {
private Integer oid;
private Integer user_id;
private String number;
private Date time;
private String note;
// private Users users;
//訂單明細集合
// private List<Orders_detail> detailList;
public Integer getOid() {
return oid;
}
public void setOid(Integer oid) {
this.oid = oid;
}
public Integer getUser_id() {
return user_id;
}
public void setUser_id(Integer user_id) {
this.user_id = user_id;
}
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
public Date getTime() {
return time;
}
public void setTime(Date time) {
this.time = time;
}
public String getNote() {
return note;
}
public void setNote(String note) {
this.note = note;
}
@Override
public String toString() {
return "Orders{" +
"oid=" + oid +
", user_d=" + user_id +
", number='" + number + '\'' +
", time=" + time +
", note='" + note + '\'' +
'}';
}
}
Orders.Ext.java
package com.hardes.pojos;
import java.util.Date;
public class OrdersExt extends Orders {
private String username;
private Date birthday;
private char sex;
private String address;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public char getSex() {
return sex;
}
public void setSex(char sex) {
this.sex = sex;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "OrdersExt{" +
"username='" + username + '\'' +
", birthday=" + birthday +
", sex=" + sex +
", address='" + address + '\'' +
", "+super.toString()+
'}';
}
}
8, 測試代碼
package com.hardes;
import com.hardes.mappers.OrdersMapper;
import com.hardes.pojos.OrdersExt;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import java.util.List;
public class TestUsers {
@Test
public void userTest(){
ApplicationContext ac = new ClassPathXmlApplicationContext("spring/applicationContext.xml");
/**
* 使用resultType作映射,查詢訂單orders 并關聯users的資訊
*/
OrdersMapper ordersmapper= (OrdersMapper) ac.getBean("ordersMapper");
List<OrdersExt> list = ordersmapper.findOrdersAndUsersByOid(2);
System.out.println(list);
}
}
測試結果
[OrdersExt{username='Tom', birthday=Sun Oct 06 08:00:00 SGT 2019, sex=M, address='Jurong East', Orders{oid=null, user_d=1, number='2000', time=Mon Oct 07 21:47:26 SGT 2019, note='bread'}}]
9, 遇到問題
Orders{oid=null, 這裡的值一直為空,說明資料庫table的列明與實體類的屬性的名字不一樣,
透過大神的部落格才明白:
查詢出來的結果的列名需要對應我們編寫的輸出映射類型中的屬性名,如果不比對,則不能完成映射,那麼查詢出來的結果也不能如願的放入對應的對象中去
resultType和resultMap