MyBatis框架基于Annotation注解的多对多关联映射

╰半夏微凉° 2022-06-18 08:28 239阅读 0赞

代码：

mybatis-config.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>
    	<properties resource="db.properties"/>
    	
    	<settings>
    		<setting name="logImpl" value="LOG4J"/>
    		
    		<setting name="lazyLoadingEnabled" value="true"/>
    		<setting name="aggressiveLazyLoading" value="false"/>
    	</settings>
    	
    	<environments default="mysql">
    	
        <environment id="mysql">
        
          <transactionManager type="JDBC"/>
          
          <dataSource type="POOLED">
            <property name="driver" value="${driver}"/>
            <property name="url" value="${url}"/>
            <property name="username" value="${username}"/>
            <property name="password" value="${password}"/>
          </dataSource>
        </environment>
      </environments>
      
      <mappers>
      	<mapper class="com.mapper.UserMapper"/> 
      	<mapper class="com.mapper.OrderMapper"/> 
      	<mapper class="com.mapper.ArticleMapper"/> 
      </mappers>
    </configuration>

Article.java

package com.bean;
    
    import java.io.Serializable;
    import java.util.List;
    
    public class Article implements Serializable {
    	
    	private Integer id;		// 商品id，主键
    	private String name;	// 商品名称
    	private Double price;	// 商品价格
    	private String remark;	// 商品描述
    	
    	// 商品和订单是多对多的关系，即一种商品可以包含在多个订单中
    	private List<Order> orders;
    
    	public Article() {
    		super();
    		// TODO Auto-generated constructor stub
    	}
    
    	public Article(String name, Double price, String remark) {
    		super();
    		this.name = name;
    		this.price = price;
    		this.remark = remark;
    	}
    
    	public Integer getId() {
    		return id;
    	}
    
    	public void setId(Integer id) {
    		this.id = id;
    	}
    
    	public String getName() {
    		return name;
    	}
    
    	public void setName(String name) {
    		this.name = name;
    	}
    
    	public Double getPrice() {
    		return price;
    	}
    
    	public void setPrice(Double price) {
    		this.price = price;
    	}
    
    	public String getRemark() {
    		return remark;
    	}
    
    	public void setRemark(String remark) {
    		this.remark = remark;
    	}
    
    	public List<Order> getOrders() {
    		return orders;
    	}
    
    	public void setOrders(List<Order> orders) {
    		this.orders = orders;
    	}
    
    	@Override
    	public String toString() {
    		return "Article [id=" + id + ", name=" + name + ", price=" + price + ", remark=" + remark + "]";
    	}
    
    }

Order.java

package com.bean;
    
    import java.io.Serializable;
    import java.util.List;
    
    public class Order implements Serializable {
    
    	private Integer id;  // 订单id，主键
    	private String code;  // 订单编号
    	private Double total; // 订单总金额
    	
    	// 订单和用户是多对一的关系，即多个订单只属于一个用户
    	private User user;
    	
    	// 订单和商品是多对多的关系，即一个订单可以包含多种商品
    	private List<Article> articles;
    
    	public Order() {
    		super();
    		// TODO Auto-generated constructor stub
    	}
    
    	public Order(String code, Double total) {
    		super();
    		this.code = code;
    		this.total = total;
    	}
    
    	public Integer getId() {
    		return id;
    	}
    
    	public void setId(Integer id) {
    		this.id = id;
    	}
    
    	public String getCode() {
    		return code;
    	}
    
    	public void setCode(String code) {
    		this.code = code;
    	}
    
    	public Double getTotal() {
    		return total;
    	}
    
    	public void setTotal(Double total) {
    		this.total = total;
    	}
    
    	public User getUser() {
    		return user;
    	}
    
    	public void setUser(User user) {
    		this.user = user;
    	}
    
    	public List<Article> getArticles() {
    		return articles;
    	}
    
    	public void setArticles(List<Article> articles) {
    		this.articles = articles;
    	}
    
    	@Override
    	public String toString() {
    		return "Order [id=" + id + ", code=" + code + ", total=" + total + "]";
    	}
    	
    	
    }

User.java

package com.bean;
    
    import java.io.Serializable;
    import java.util.List;
    
    public class User implements Serializable{
    	
    	private Integer id;  // 用户id，主键
    	private String username;  // 用户名
    	private String loginname; // 登录名
    	private String password;  // 密码
    	private String phone;    // 联系电话
    	private String address;  // 收货地址
    	
    	// 用户和订单是一对多的关系，即一个用户可以有多个订单
    	private List<Order> orders;
    
    	public User() {
    		super();
    		// TODO Auto-generated constructor stub
    	}
    
    	public User(String username, String loginname, String password, String phone, String address) {
    		super();
    		this.username = username;
    		this.loginname = loginname;
    		this.password = password;
    		this.phone = phone;
    		this.address = 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 String getLoginname() {
    		return loginname;
    	}
    
    	public void setLoginname(String loginname) {
    		this.loginname = loginname;
    	}
    
    	public String getPassword() {
    		return password;
    	}
    
    	public void setPassword(String password) {
    		this.password = password;
    	}
    
    	public String getPhone() {
    		return phone;
    	}
    
    	public void setPhone(String phone) {
    		this.phone = phone;
    	}
    
    	public String getAddress() {
    		return address;
    	}
    
    	public void setAddress(String address) {
    		this.address = address;
    	}
    
    	public List<Order> getOrders() {
    		return orders;
    	}
    
    	public void setOrders(List<Order> orders) {
    		this.orders = orders;
    	}
    
    	@Override
    	public String toString() {
    		return "User [id=" + id + ", username=" + username + ", loginname=" + loginname + ", password=" + password + ", phone=" + phone
    				+ ", address=" + address + "]";
    	}
    
    
    }

FKSqlSessionFactory.java

package com.factory;
    
    import java.io.InputStream;
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    public class FKSqlSessionFactory {
    	
    	private static SqlSessionFactory sqlSessionFactory = null;
    	
    	// 初始化创建SqlSessionFactory对象
    	static{
    		try {
    			// 读取mybatis-config.xml文件
    			InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
    			sqlSessionFactory = new SqlSessionFactoryBuilder()
    					.build(inputStream);
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    	}
    	
    	// 获取SqlSession对象的静态方法
    	public static SqlSession getSqlSession(){
    		return sqlSessionFactory.openSession();
    	}
    
    	// 获取SqlSessionFactory的静态方法
    	public static SqlSessionFactory getSqlSessionFactory() {
    		return sqlSessionFactory;
    	}
    
    }

ArticleMapper.xml

package com.mapper;
    
    import java.util.List;
    
    import org.apache.ibatis.annotations.Select;
    
    import com.bean.Article;
    import com.bean.User;
    
    public interface ArticleMapper {
       @Select("select * from tb_article where id in (select article_id from tb_item where order_id = #{id})")
       List<Article> selectByOrderId(Integer order_id);
    }

OrderMapper.xml

package com.mapper;
    
    import org.apache.ibatis.annotations.Many;
    import org.apache.ibatis.annotations.One;
    import org.apache.ibatis.annotations.Result;
    import org.apache.ibatis.annotations.Results;
    import org.apache.ibatis.annotations.Select;
    import org.apache.ibatis.mapping.FetchType;
    
    import com.bean.Order;
    
    public interface OrderMapper {
         @Select("select * from tb_order where id = #{id}")
         @Results({
        	@Result(id=true,column="id",property="id"),
     		@Result(column="code",property="code"),
     		@Result(column="total",property="total"),
     		@Result(column="user_id",property="user",
     		one=@One(select="com.mapper.UserMapper.selectById",fetchType=FetchType.EAGER)),
     		@Result(column="id",property="articles",many=@Many(select="com.mapper.ArticleMapper.selectByOrderId",fetchType=FetchType.LAZY))
         })
          Order selectById(Integer id);
    }

UserMapper.xml

package com.mapper;
    
    import org.apache.ibatis.annotations.Select;
    
    import com.bean.User;
    
    public interface UserMapper {
    	 @Select("select * from tb_user where id = #{id}")
    	 User selectById(Integer id);
    }

ManyToManyTest.java

package com.test;
    
    import org.apache.ibatis.session.SqlSession;
    
    import com.bean.Order;
    import com.factory.FKSqlSessionFactory;
    import com.mapper.OrderMapper;
    
    public class ManyToManyTest {
    
    	public static void main(String[] args) {
    		// TODO Auto-generated method stub
    		SqlSession session = FKSqlSessionFactory.getSqlSession();
    		OrderMapper om = session.getMapper(OrderMapper.class);
    		Order order =om.selectById(1);
    		// 查看查询到的Order对象
    		System.out.println(order.getId() + " " + order.getCode() + " " + order.getTotal());
    		// 查看Order关联的User对象
    		System.out.println(order.getUser());
    		// 查看关联的Article集合，因为配置使用的是LAZY懒加载，所以当使用时才执行SQL语句
    	    order.getArticles().forEach(article -> System.out.println(article));
    	    session.commit();
    	    session.close();
    	}
    
    }

截图：

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[Center]: /images/20220618/c3745c8e545e44b49988aac1ea7bcb04.png