Mybaits中映射关系一对多（二）

一对多的话，这里用到的是Customer跟LinkMan，一个customer对应多个linkman。（表的关系见hibernate映射关系中的表）

1、创建实体

LinkMan.java

package com.nieshenkuan.model;

public class LinkMan {
    // CREATE TABLE linkman(
    // lkm_id BIGINT(32) PRIMARY KEY auto_increment,
    // lkm_name VARCHAR(32) NOT NULL,
    // lkm_sex CHAR(1),
    // lkm_phone VARCHAR(16),
    // lkm_cus_id BIGINT(32),
    // CONSTRAINT fk_cus_lkm FOREIGN KEY(lkm_cus_id) REFERENCES customer(cus_id)
    // )ENGINE=INNODB CHARSET=utf8;
    private Long lkm_id;
    private String lkm_name;
    private Character lkm_sex;
    private String lkm_phone;
    private Long lkm_cus_id;

    public Long getLkm_id() {
        return lkm_id;
    }

    public void setLkm_id(Long lkm_id) {
        this.lkm_id = lkm_id;
    }

    public String getLkm_name() {
        return lkm_name;
    }

    public void setLkm_name(String lkm_name) {
        this.lkm_name = lkm_name;
    }

    public Character getLkm_sex() {
        return lkm_sex;
    }

    public void setLkm_sex(Character lkm_sex) {
        this.lkm_sex = lkm_sex;
    }

    public String getLkm_phone() {
        return lkm_phone;
    }

    public void setLkm_phone(String lkm_phone) {
        this.lkm_phone = lkm_phone;
    }

    public Long getLkm_cus_id() {
        return lkm_cus_id;
    }

    public void setLkm_cus_id(Long lkm_cus_id) {
        this.lkm_cus_id = lkm_cus_id;
    }

    @Override
    public String toString() {
        return "LinkMan [lkm_id=" + lkm_id + ", lkm_name=" + lkm_name + ", lkm_sex=" + lkm_sex + ", lkm_phone="
                + lkm_phone + ", lkm_cus_id=" + lkm_cus_id + "]";
    }
    

}

Customer.java

package com.nieshenkuan.model;

import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class Customer {
//  CREATE table customer(
//          cus_id BIGINT(32) PRIMARY KEY auto_increment,
//          cus_name VARCHAR(32) NOT NULL,
//          cus_mobile VARCHAR(32) DEFAULT NULL,

//          )ENGINE=INNODB CHARSET=utf8;
    private Long cus_id;
    private String cus_name;
    private String cus_mobile;

    private List linkMan;
    
    
    public Long getCus_id() {
        return cus_id;
    }
    public void setCus_id(Long cus_id) {
        this.cus_id = cus_id;
    }
    public String getCus_name() {
        return cus_name;
    }
    public void setCus_name(String cus_name) {
        this.cus_name = cus_name;
    }
    public String getCus_mobile() {
        return cus_mobile;
    }
    public void setCus_mobile(String cus_mobile) {
        this.cus_mobile = cus_mobile;
    }
    public List getLinkMan() {
        return linkMan;
    }
    public void setLinkMan(List linkMan) {
        this.linkMan = linkMan;
    }
    @Override
    public String toString() {
        return "Customer [cus_id=" + cus_id + ", cus_name=" + cus_name + ", cus_mobile=" + cus_mobile + ", linkMan="
                + linkMan + "]";
    }
    
    
    
}

2、创建CustomerMapper.xml文件

    
        
        
        
        
            
            
            
            
            
        
    
    
    
    
        SELECT c.*,l.*
        FROM customer c, linkman l
        WHERE c.cus_id=l.lkm_cus_id and c.cus_id=#{cus_id}
  

3、创建dao接口CustomerMapper.java

package com.nieshenkuan.dao;

import com.nieshenkuan.model.Customer;

public interface CustomerMapper {
    
    public Customer getCustomer(Long id);
}

4、将CustomerMapper.xml注册到sqlMapperConfig.xml文件中去

5、测试

package com.nieshenkuan.test;

import java.io.IOException;

import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import com.nieshenkuan.dao.CustomerMapper;
import com.nieshenkuan.model.Customer;
import com.nieshenkuan.util.MyBatisUtil;

public class TestOneToMany {
    @Test
    public void test1() throws IOException {
        SqlSession sqlSession = MyBatisUtil.getSqlSession();
/**
 * 这里是一对多的实例
 * 
 */
        /*1、一对多就是利用collection关键字来弄得。
         * 首先，这里是是从一的一方，通过查到一的一方，并把对应多的数据也查出来。
         * 一个顾客对应多个联系人。即一个customer对应多个linkman
         * */
        /*
         * 2、查找到customer，就能把所有的linkman也顺带查出来。
         * 这里也是通过外键的形式，外键建在多的一方，即linkman这一方
         * linkman这一数据库对应的实体有一个字段作为外键，指向customer的主键。
         * 从而从linkman到customer形成多对一的关系
         * 从customer到linkman形成一对多的关系。
         * 
         * 如果我们要从customer中找到多的一方，要用collection集合带出所有的查询结果。
         * 这点在mapper.xml文件中显现的很明显。
         * */
        CustomerMapper customerMapper=sqlSession.getMapper(CustomerMapper.class);
        Customer customer=customerMapper.getCustomer(2l);
        System.out.println(customer);
    }
}

6、测试结果

Customer [cus_id=2, cus_name=阿里巴巴, cus_mobile=null, linkMan=[LinkMan [lkm_id=3, lkm_name=马云, lkm_sex=null, lkm_phone=null, lkm_cus_id=2], LinkMan [lkm_id=4, lkm_name=基哥, lkm_sex=null, lkm_phone=null, lkm_cus_id=2]]]