基于Maven框架的整体设计 ―― 一多一的关系

思路：导入mybatis、mysql、Junit4.13依赖；

编写两个java实体类；

编写sqMapConfig.xml mybatis核心配置文件

编写dao层接口；

编写mapper 映射文件；

编写测试类。

1.导入相关依赖

<!--配置依赖-->
<dependencies>
  <!--配置mybatis-->
  <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.5.2</version>
  </dependency>

  <!--配合mysql-->
  <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.47</version>
  </dependency>

  <!--配置单元测试-->
  <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.13</version>
  </dependency>
</dependencies>

2.编写两个java实体类；

Students

package com.mybatis.pojo;


public class Students {

  private Integer sid;
  private String sName;
  private Integer sCid;
  private Cards cards;   //  一多一的关系


  public Integer getSid() {
      return sid;
  }

  public void setSid(Integer sid) {
      this.sid = sid;
  }

  public String getsName() {
      return sName;
  }

  public void setsName(String sName) {
      this.sName = sName;
  }

  public Integer getsCid() {
      return sCid;
  }

  public void setsCid(Integer sCid) {
      this.sCid = sCid;
  }

  public Cards getCards() {
      return cards;
  }

  public void setCards(Cards cards) {
      this.cards = cards;
  }

  @Override
  public String toString() {
      return "Students{" +
              "sid=" + sid +
              ", sName='" + sName + '\'' +
              ", sCid=" + sCid +
              ", cards=" + cards +
              '}';
  }
}

Cards

package com.mybatis.pojo;

public class Cards {

  private Integer cid;
  private String cnum;

  public Integer getCid() {
      return cid;
  }

  public void setCid(Integer cid) {
      this.cid = cid;
  }

  public String getCnum() {
      return cnum;
  }

  public void setCnum(String cnum) {
      this.cnum = cnum;
  }

  @Override
  public String toString() {
      return "Cards{" +
              "cid=" + cid +
              ", cnum='" + cnum + '\'' +
              '}';
  }
}

3.编写sqMapConfig.xml mybatis核心配置文件

<?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>

  <!--
  配置外部文件properties文件
  -->
  <properties resource="jdbc.properties"></properties>

  <!--配置实体类相对路径 别名-->
  <typeAliases>
      <typeAlias type="com.mybatis.pojo.Students" alias="Stu"></typeAlias>
      <typeAlias type="com.mybatis.pojo.Cards" alias="Car"></typeAlias>
  </typeAliases>

  <!--配置mybatis环境-->
  <environments default="mybatis">
      <environment id="mybatis">
          <transactionManager type="jdbc"></transactionManager>
          <dataSource type="pooled">
              <property name="driver" value="${jdbc.driver}"></property>
              <property name="url" value="${jdbc.url}"></property>
              <property name="username" value="${jdbc.username}"></property>
              <property name="password" value="${jdbc.password}"></property>
          </dataSource>
      </environment>
  </environments>

  <!--
  配置mapper.xml映射文件
  resource:相对路径
  -->
  <mappers>
      <mapper resource="com.mybatis.dao/studentsDao.xml"></mapper>
      <mapper resource="com.mybatis.dao/CardsDao.xml"></mapper>
      <!--<package name="com.mybatis.dao"></package>-->
  </mappers>
</configuration>

4.编写dao层接口；

package com.mybatis.dao;

import com.mybatis.pojo.Students;

import java.util.List;

public interface StudentsDao {

  // 查询学生信息以及对应的身份证信息
  public List<Students> findAll();
}

还有一个略了；

5.编写mapper 映射文件；

StudentsDao.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 值是dao层对应的接口-->
<mapper namespace="com.mybatis.dao.StudentsDao">

  <!--
  配置实体类字段与数据库字段一致
  -->
  <resultMap id="stuMap" type="Stu">
      <id property="sid" column="sid"></id>
      <result property="sName" column="sname"></result>
      <result property="sCid" column="scid"></result>
      <association property="cards" resultMap="com.mybatis.dao.CardsDao.cardsMap"></association>
  </resultMap>

  <!--
  查询学生信息以及对应的身份证信息
  resultMap：实体类与数据库映射的数据类型
  -->
  <select id="findAll" resultMap="stuMap">
      select s.sname,c.cnum from students s,cards c where s.scid=c.cid;
  </select>
</mapper>

CardsDao.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 值是dao层对应接口的权限定名-->
<mapper namespace="com.mybatis.dao.CardsDao">
  <!--配置实体类字段与数据库一致-->
  <resultMap id="cardsMap" type="car">
      <!--
      property：实体字段
      column：数据库字段
      -->
      <id property="cid" column="cid"></id>
      <result property="cnum" column="cnum"></result>
  </resultMap>
</mapper>

6.编写测试类

import com.mybatis.dao.StudentsDao;
import com.mybatis.pojo.Students;
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.IOException;
import java.io.InputStream;
import java.util.List;

public class TestMybatis {

  InputStream resource;
  SqlSession session;
  StudentsDao stuDao;
  @Before  // 在test方法之前执行
  public void init() throws IOException {

      // 加载核心配置文件
      resource = Resources.getResourceAsStream("sqMapConfig.xml");
      // 创建sqlSessionFactoryBuilder对象
      SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
      // 创建sqlSessionFactory对象
      SqlSessionFactory build = builder.build(resource);
      // 创建Session对象
      session = build.openSession();
      // 执行方法
      stuDao = session.getMapper(StudentsDao.class);

  }
  @After // 在test方法之后执行
  public void close() throws IOException {
      // 关闭资源
      session.close();
      resource.close();
  }

  @Test
  public void test01(){
      List<Students> list = stuDao.findAll();
      for (Students students : list) {
          System.out.println(students);
      }

  }
}

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原文链接：https://www.cnblogs.com/vctM/p/15407045.html

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