Mybatis 多对多_注解

最新推荐文章于 2024-08-09 09:18:29 发布

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本文详细解析了MyBatis的配置文件结构，包括数据源、事务管理、类型别名、映射器等核心组件的设置。通过具体代码示例，展示了如何使用MyBatis进行SQL查询、结果映射及关联对象处理，适用于初学者理解和实践MyBatis框架。

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>
    <typeAliases>
        <package name="com.how2java.pojo"/>
    </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://localhost:3306/how2java?characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="admin"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper class="com.how2java.mapper.OrderItemMapper"/>
        <mapper class="com.how2java.mapper.OrderMapper"/>
        <mapper class="com.how2java.mapper.ProductMapper"/>
    </mappers>
</configuration>

OrderItemMapper.java

package com.how2java.mapper;
 
import java.util.List;
 
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 com.how2java.pojo.OrderItem;
 
public interface OrderItemMapper {
     
    @Select(" select * from order_item_ where oid = #{oid}")
    @Results({ 
        @Result(property="product",column="pid",one=@One(select="com.how2java.mapper.ProductMapper.get")) 
    }) 
    public List<OrderItem> listByOrder(int oid);
}

OrderItem.java

package com.how2java.pojo;

public class OrderItem {
    private int id;
    private int number;
    private Order order;
    private Product product;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public int getNumber() {
        return number;
    }
    public void setNumber(int number) {
        this.number = number;
    }
    public Order getOrder() {
        return order;
    }
    public void setOrder(Order order) {
        this.order = order;
    }
    public Product getProduct() {
        return product;
    }
    public void setProduct(Product product) {
        this.product = product;
    }

}

OrderMapper.java

package com.how2java.mapper;
 
import java.util.List;
 
import org.apache.ibatis.annotations.Many;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
 
import com.how2java.pojo.Order;
 
public interface OrderMapper {
    @Select("select * from order_")
     @Results({
            @Result(property = "id", column = "id"),
            @Result(property = "orderItems", javaType = List.class, column = "id", 
                    many = @Many(select = "com.how2java.mapper.OrderItemMapper.listByOrder"))
            })      
    public List<Order> list();
     
}

Order.java

package com.how2java.pojo;

        import java.util.List;

public class Order {
    private int id;
    private String code;

    List<OrderItem> orderItems;

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getCode() {
        return code;
    }
    public void setCode(String code) {
        this.code = code;
    }
    public List<OrderItem> getOrderItems() {
        return orderItems;
    }
    public void setOrderItems(List<OrderItem> orderItems) {
        this.orderItems = orderItems;
    }

}

ProductMapper.java

package com.how2java.mapper;

import org.apache.ibatis.annotations.Select;

import com.how2java.pojo.Product;

public interface ProductMapper {

    @Select("select * from product_ where id = #{id}")
    public Product get(int id);
}

Product.java

package com.how2java.pojo;

public class Product {
    private int id;
    private String name;
    private float price;
    private Category category;

    public Category getCategory() {
        return category;
    }
    public void setCategory(Category category) {
        this.category = category;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public float getPrice() {
        return price;
    }
    public void setPrice(float price) {
        this.price = price;
    }
    @Override
    public String toString() {
        return "Product [id=" + id + ", name=" + name + ", price=" + price + "]";
    }

}

Category.java

package com.how2java.pojo;

import java.util.List;

public class Category {
    private int id;
    private String name;
    List<Product> products;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public List<Product> getProducts() {
        return products;
    }
    public void setProducts(List<Product> products) {
        this.products = products;
    }
    @Override
    public String toString() {
        return "Category [id=" + id + ", name=" + name + "]";
    }

}

TestMybatis.java

package com.how2java;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

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.how2java.mapper.OrderMapper;
import com.how2java.pojo.Order;
import com.how2java.pojo.OrderItem;
import com.how2java.pojo.Product;

public class TestMybatis {

    public static void main(String[] args) throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        listOrder(session);

        session.commit();
        session.close();

    }

    private static void listOrder(SqlSession session) {
        OrderMapper mapper =session.getMapper(OrderMapper.class);
        List<Order> os = mapper.list();
        for (Order o : os) {
            System.out.println(o.getCode());
            List<OrderItem> ois= o.getOrderItems();
            if(null!=ois){
                for (OrderItem oi : ois) {
                    System.out.format("\t%s\t%f\t%d%n", oi.getProduct().getName(),oi.getProduct().getPrice(),oi.getNumber());
                }
            }

        }
    }
}