Mybatis表关联一对一
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1Mybatis表关联一对一简介
此章节是讲解两个具备一对一关系的实体,在mybatis中如何配置映射文件,如何处理这个一对一的关系。
2Mybatis一对一的编码核心步骤
1)环境前期准备
2)创建基于maven的工程MyBatis
3)创建持久化的实体类Course和Catalog,
两个实体一对一的关系,一个课程属于一个目录分类
4)配置数据库连接信息configure.xml
5)配置mybatis的sql语句,在配置文件onetoone.xml中
此配置文件主要涵盖一对一的关系映射,和基于这个关系的查询
6)创建测试类TestOneToOne
7)测试结果展示
3Mybatis一对一编码之:环境前期准备
第一步:准备开发工具
Eclipse Neon 4.6.0
JDK 1.8
第二步:准备数据库:
1) 创建mysql数据实例:template
2) 创建表course和catalog,含有如下字段:
course表:
id:int(11)类型
coursename:varchar(45)类型
catalogid:int(11)类型
catalog表:
id:int(11)类型
catalogname:varchar(45)类型
第三步:往数据库中初始化数据:
course表初始化:
INSERT INTO `course` VALUES ('3', 'course3', '3');
catalog表初始化:
INSERT INTO `catalog` VALUES ('3', 'catalog3');
4Mybatis一对一编码之:创建基于maven的工程MyBatis
第一步:基于Maven创建工程MyBatis
第二步:配置工程依赖的jar包,在pom.xml中:
<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.test</groupId>
<artifactId>MyBatis</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>MyBatis</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<spring.version>4.1.4.RELEASE</spring.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</artifactId>
<version>1.1.3</version>
</dependency>
<dependency>
<groupId>commons-dbcp</groupId>
<artifactId>commons-dbcp</artifactId>
<version>1.4</version>
</dependency>
<dependency>
<groupId>commons-pool</groupId>
<artifactId>commons-pool</artifactId>
<version>1.6</version>
</dependency>
<dependency>
<groupId>org.codehaus.jackson</groupId>
<artifactId>jackson-mapper-asl</artifactId>
<version>1.9.13</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>2.6.1</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.6.1</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.6.1</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-orm</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis-spring</artifactId>
<version>1.2.3</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.36</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.3.0</version>
</dependency>
<dependency>
<groupId>c3p0</groupId>
<artifactId>c3p0</artifactId>
<version>0.9.1.2</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
</dependencies>
</project>
第三步:按照如下工程结构创建相关文件:
5Mybatis一对一编码之:创建持久化的实体类Course和Catalog
第一步:创建包:com.test.model
第二步:在该包下创建Course和Catalog
Course类:
package com.test.model;
public class Course {
private long id;
private String coursename;
private Catalog catalog;
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getCoursename() {
return coursename;
}
public void setCoursename(String coursename) {
this.coursename = coursename;
}
public Catalog getCatalog() {
return catalog;
}
public void setCatalog(Catalog catalog) {
this.catalog = catalog;
}
}
Catalog类
package com.test.model;
public class Catalog {
private long id;
private String catalogname;
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getCatalogname() {
return catalogname;
}
public void setCatalogname(String catalogname) {
this.catalogname = catalogname;
}
}
6一对一编码之:配置数据库连接信息configure.xml
第一步:创建文件夹src/main/resources
第二步: 创建包:config.ch03
第三步:在该包下创建配置文件
补充:该配置文件的核心节点介绍如下:
typeAliases节点:类型命名,作用是为java类命别名,从而减少后续应用别名的冗余;
environments节点:配置mybatis连接的基础环境的。比如:事务管理器,数据库连接信息等;
mappers节点:映射器,配置mybatis的映射文件的位置信息等
<?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>
<typeAliases>
<typeAlias alias="Course" type="com.test.model.Course" />
<typeAlias alias="Catalog" type="com.test.model.Catalog" />
</typeAliases>
<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://127.0.0.1:3306/template" />
<property name="username" value="root" />
<property name="password" value="123456" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/test/ch03/onetoone.xml" />
</mappers>
</configuration>
7Mybatis一对一编码之:配置mybatis的sql语句,在配置文件onetoone.xml中
第一步:创建包:com.test.ch03
第二步:在该包下创建配置文件
补充:association节点就是配置一对一关系的
<?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.test.ch03.CourseMapper">
<resultMap type="Course" id="resultCourseMap">
<result property="id" column="id" />
<result property="coursename" column="coursename" />
<association property="catalog" javaType="Catalog">
<id column="id" property="id" />
<result column="catalogname" property="catalogname" />
</association>
</resultMap>
<select id="getCourse" resultMap="resultCourseMap" parameterType="int">
SELECT c.coursename,ct.catalogname
FROM course c, catalog ct
WHERE c.catalogid=ct.id AND c.id=#{id}
</select>
</mapper>
8Mybatis一对一编码之:编写测试类
在包:com.test.ch03下创建测试类:
TestOneToOne类
package com.test.ch03;
import java.io.Reader;
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 com.test.model.Catalog;
import com.test.model.Course;
public class TestOneToOne {
private static SqlSessionFactory sqlSessionFactory;
private static Reader reader;
static {
try {
reader = Resources.getResourceAsReader
("config/ch03/Configure.xml");
sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
SqlSession session = sqlSessionFactory.openSession();
try {
Course c = session.selectOne("com.test.ch03.CourseMapper.getCourse", 3);
System.out .println("coursename: " + c.getCoursename());
Catalog catalog = c.getCatalog();
System.out .println("catalogname: " + catalog.getCatalogname());
} finally {
session.close();
}
}
}
9Mybatis一对一编码之:结果展示
log4j:WARN No appenders could be found for logger (org.apache.ibatis.logging.LogFactory).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
coursename: course3
catalogname: catalog3
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