MyBatis实现多表查询——案例：订单

一、数据库表创建

• users用户表、products商品表、types商品类型表、orders订单表、details订单详情表
• 表结构.png
• details.png
• orders.png
• products.png
• types.png
• users.png

二、使用MyBatis完成相应的查询功能

• pom.xml 文件添加 junit，mysql， mybatis 依赖。

  
  
      4.0.0
      com
      Mybatis
      1.0-SNAPSHOT
      
          
              mysql
              mysql-connector-java
              8.0.18
          
          
              junit
              junit
              4.12
          
          
              org.mybatis
              mybatis
              3.4.6
          
      
  
  

• 设置MyBatis的配置文件 mybatis.xml

• db.properties数据库的配置文件
  • mysql版本不同driver要修改

  driver=com.mysql.cj.jdbc.Driver
  url=jdbc:mysql://localhost:3307/mysqls?serverTimezone=UTC
  user=root
  pass=123456
  

• 设计 pojo 相关类
  • Users.java

    public class Users {
        private int uid;
        private String name;
        private String pass;
        private String phone;
        public int getUid() { return uid; }
        public void setUid(int uid) { this.uid = uid; }
        public String getName() { return name; }
        public void setName(String name) { this.name = name; }
        public String getPass() { return pass; }
        public void setPass(String pass) { this.pass = pass; }
        public String getPhone() { return phone; }
        public void setPhone(String phone) { this.phone = phone; }
        @Override
        public String toString() {
            final StringBuffer sb = new StringBuffer("Users{");
            sb.append("uid=").append(uid);
            sb.append(", name='").append(name).append('\'');
            sb.append(", pass='").append(pass).append('\'');
            sb.append(", phone='").append(phone).append('\'');
            sb.append('}');
            return sb.toString();
        }
    }
    

  • Order.java

    public class Order {
        private String oid;
        private double price;
        private String addr;
        private String payType;
        private Users u;
        private List details;
        public String getOid() { return oid; }
        public void setOid(String oid) { this.oid = oid; }
        public double getPrice() { return price; }
        public void setPrice(double price) { this.price = price; }
        public String getAddr() { return addr; }
        public void setAddr(String addr) { this.addr = addr; }
        public String getPayType() { return payType; }
        public void setPayType(String payType) { this.payType = payType; }
        public Users getU() { return u; }
        public void setU(Users u) { this.u = u; }
        public List getDetails() { return details; }
        public void setDetails(List details) { this.details = details; }
        @Override
        public String toString() {
            final StringBuffer sb = new StringBuffer("Order{");
            sb.append("oid='").append(oid).append('\'');
            sb.append(", price=").append(price);
            sb.append(", addr='").append(addr).append('\'');
            sb.append(", payType='").append(payType).append('\'');
            sb.append(", u=").append(u);
            sb.append(", details=").append(details);
            sb.append('}');
            return sb.toString();
        }
    }
    

  • Product.java

    public class Product {
        private String pid;
        private String name;
        private String img;
        private double price;
        private Types t;
        public String getPid() { return pid; }
        public void setPid(String pid) { this.pid = pid; }
        public String getName() { return name; }
        public void setName(String name) { this.name = name; }
        public String getImg() { return img; }
        public void setImg(String img) { this.img = img; }
        public double getPrice() { return price; }
        public void setPrice(double price) { this.price = price; }
        public Types getT() { return t; }
        public void setT(Types t) { this.t = t; }
        @Override
        public String toString() {
            final StringBuffer sb = new StringBuffer("Product{");
            sb.append("pid='").append(pid).append('\'');
            sb.append(", name='").append(name).append('\'');
            sb.append(", img='").append(img).append('\'');
            sb.append(", price=").append(price);
            sb.append(", t=").append(t);
            sb.append('}');
            return sb.toString();
        }
    }
    

  • Types.java

    public class Types {
        private String tid;
        private String name;
        public String getTid() { return tid; }
        public void setTid(String tid) { this.tid = tid; }
        public String getName() { return name; }
        public void setName(String name) { this.name = name; }
        @Override
        public String toString() {
            final StringBuffer sb = new StringBuffer("Types{");
            sb.append("tid='").append(tid).append('\'');
            sb.append(", name='").append(name).append('\'');
            sb.append('}');
            return sb.toString();
        }
    }
    

  • Detail.java

    public class Detail {
        private String did;
        private int count;
        private Product pro;
        public String getDid() { return did; }
        public void setDid(String did) { this.did = did; }
        public int getCount() { return count; }
        public void setCount(int count) { this.count = count; }
        public Product getPro() { return pro; }
        public void setPro(Product pro) { this.pro = pro; }
        @Override
        public String toString() {
            final StringBuffer sb = new StringBuffer("Detail{");
            sb.append("did='").append(did).append('\'');
            sb.append(", count=").append(count);
            sb.append(", pro=").append(pro);
            sb.append('}');
            return sb.toString();
        }
    }
    

• 设置映射文件mapper
  • namespace和id组合唯一,可自定义
  • 使用resultMap进行联合查询，对应pojo内的属性名(property)和数据库表中的列名相同,可省略不写result标签
  • 使用association标签进行对一的表结构联合查询
  • 使用collection标签进行对多的表结构联合查询
  • UserMapper.xml

    
    
    
        
          select * from users where uid = #{uid}
        
    
    

  • OrderMapper.xml

    
    
    
        
          select * from orders where oid = #{oid}
        
        
            
            
            
            
            
            
        
    
    

  • DetailMapper.xml

    
    
    
        
          select * from details where oid = #{oid}
        
        
            
            
            
        
    
    

  • TypeMapper.xml

    
    
    
        
          select * from types where tid = #{tid}
        
    
    

  • ProductMapper.xml

    
    
    
        
          select * from products where pid = #{uid}
        
        
            
            
        
    
    

• 测试类 Test.java

  public class TestOrders {
      private SqlSessionFactory sf = null;
      private SqlSession session = null;
      @Before
      public void setUp(){
          try {
              sf = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis.xml"));
              session = sf.openSession();
          } catch (IOException e) {
              e.printStackTrace();
          }
      }
      @After
      public void tearDown(){
          if(session != null){
              session.close();
              session = null;
          }
      }
      @Test
      public void testGetOrderByOid(){
          Order order = session.selectOne("com.pojo.OrderMapper.getOrderByOid", "bfa2974d62cc11eaa62b8cec4b26e06a");
          System.out.println(order);
      }
  }
  

• 测试结果

  Opening JDBC Connection
  Created connection 1881561036.
  Setting autocommit to false on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@702657cc]
  ==>  Preparing: select * from orders where oid = ? 
  ==> Parameters: bfa2974d62cc11eaa62b8cec4b26e06a(String)
  <==    Columns: oid, uid, price, payType, addr
  <==        Row: bfa2974d62cc11eaa62b8cec4b26e06a, 1, 4799.0, AAA, 支付宝
  ====>  Preparing: select * from users where uid = ? 
  ====> Parameters: 1(Integer)
  <====    Columns: uid, name, pass, phone
  <====        Row: 1, LKT, 123456, 18111111111
  <====      Total: 1
  ====>  Preparing: select * from details where oid = ? 
  ====> Parameters: bfa2974d62cc11eaa62b8cec4b26e06a(String)
  <====    Columns: did, count, oid, pid
  <====        Row: 304adbc162cd11eaa62b8cec4b26e06a, 2, bfa2974d62cc11eaa62b8cec4b26e06a, 4445ff1c62cc11eaa62b8cec4b26e06a
  ======>  Preparing: select * from products where pid = ? 
  ======> Parameters: 4445ff1c62cc11eaa62b8cec4b26e06a(String)
  <======    Columns: pid, name, img, price, tid
  <======        Row: 4445ff1c62cc11eaa62b8cec4b26e06a, BlackShark2pro, BlackShark.jpg, 3299.0, baa46abb62cb11eaa62b8cec4b26e06a
  ========>  Preparing: select * from types where tid = ? 
  ========> Parameters: baa46abb62cb11eaa62b8cec4b26e06a(String)
  <========    Columns: tid, name
  <========        Row: baa46abb62cb11eaa62b8cec4b26e06a, AAA
  <========      Total: 1
  <======      Total: 1
  <====        Row: 304bca1b62cd11eaa62b8cec4b26e06a, 1, bfa2974d62cc11eaa62b8cec4b26e06a, 70106ee762cc11eaa62b8cec4b26e06a
  ======>  Preparing: select * from products where pid = ? 
  ======> Parameters: 70106ee762cc11eaa62b8cec4b26e06a(String)
  <======    Columns: pid, name, img, price, tid
  <======        Row: 70106ee762cc11eaa62b8cec4b26e06a, BlackShark3pro, BlackShark3pro.jpg, 4799.0, baa49b9762cb11eaa62b8cec4b26e06a
  ========>  Preparing: select * from types where tid = ? 
  ========> Parameters: baa49b9762cb11eaa62b8cec4b26e06a(String)
  <========    Columns: tid, name
  <========        Row: baa49b9762cb11eaa62b8cec4b26e06a, BBB
  <========      Total: 1
  <======      Total: 1
  <====        Row: 88d56e6a62cd11eaa62b8cec4b26e06a, 1, bfa2974d62cc11eaa62b8cec4b26e06a, 70106ee762cc11eaa62b8cec4b26e06a
  <====      Total: 3
  <==      Total: 1
  Order{oid='bfa2974d62cc11eaa62b8cec4b26e06a', price=4799.0, addr='支付宝', payType='AAA', u=Users{uid=1, name='LKT', pass='123456', phone='18111111111'}, details=[Detail{did='304adbc162cd11eaa62b8cec4b26e06a', count=2, pro=Product{pid='4445ff1c62cc11eaa62b8cec4b26e06a', name='BlackShark2pro', img='BlackShark.jpg', price=3299.0, t=Types{tid='baa46abb62cb11eaa62b8cec4b26e06a', name='AAA'}}}, Detail{did='304bca1b62cd11eaa62b8cec4b26e06a', count=1, pro=Product{pid='70106ee762cc11eaa62b8cec4b26e06a', name='BlackShark3pro', img='BlackShark3pro.jpg', price=4799.0, t=Types{tid='baa49b9762cb11eaa62b8cec4b26e06a', name='BBB'}}}, Detail{did='88d56e6a62cd11eaa62b8cec4b26e06a', count=1, pro=Product{pid='70106ee762cc11eaa62b8cec4b26e06a', name='BlackShark3pro', img='BlackShark3pro.jpg', price=4799.0, t=Types{tid='baa49b9762cb11eaa62b8cec4b26e06a', name='BBB'}}}]}
  Resetting autocommit to true on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@702657cc]
  Closing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@702657cc]
  Returned connection 1881561036 to pool.