使用Mybatis進行多表聯查操作
阿新 • • 發佈：2017-12-13
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（1）增加一個測試數據庫shop_order，sql語句如下：
CREATE DATABASE `shop_order`; USE `shop_order`; CREATE TABLE `t_user` ( `id` INT(11) NOT NULL AUTO_INCREMENT, `username` VARCHAR(20) DEFAULT NULL, `password` VARCHAR(50) DEFAULT NULL, `sex` VARCHAR(2) DEFAULT NULL, `brithday` DATE DEFAULT NULL, `address`VARCHAR(200) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=INNODB AUTO_INCREMENT=20 DEFAULT CHARSET=utf8; CREATE TABLE `t_product` ( `id` INT(11) NOT NULL AUTO_INCREMENT, `name` VARCHAR(100) DEFAULT NULL, `price` FLOAT DEFAULT NULL, `description` TEXT, PRIMARY KEY (`id`) ) ENGINE=INNODB AUTO_INCREMENT=10 DEFAULT CHARSET=utf8; CREATE TABLE `t_order` ( `id` INT(11) NOT NULL AUTO_INCREMENT, `userId` INT(11) DEFAULT NULL, `createTime` DATETIME DEFAULT NULL, `state` VARCHAR(20) DEFAULT NULL, PRIMARY KEY (`id`), KEY `fk_userId` (`userId`), CONSTRAINT `fk_userId` FOREIGN KEY (`userId`) REFERENCES`t_user` (`id`) ) ENGINE=INNODB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8; CREATE TABLE `t_orderdetail` ( `id` INT(11) NOT NULL AUTO_INCREMENT, `productId` INT(11) DEFAULT NULL, `orderId` INT(11) DEFAULT NULL, `num` INT(11) DEFAULT NULL, `price` FLOAT DEFAULT NULL, PRIMARY KEY (`id`), KEY `fk_productId` (`productId`), KEY `fk_orderId` (`orderId`), CONSTRAINT `fk_orderId` FOREIGN KEY (`orderId`) REFERENCES `t_order` (`id`), CONSTRAINT `fk_productId` FOREIGN KEY (`productId`) REFERENCES `t_product` (`id`) ) ENGINE=INNODB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8; INSERT INTO `t_user`(`id`,`username`,`password`,`sex`,`brithday`,`address`) VALUES (16,‘小黃‘,‘2222‘,‘男‘,‘2014-01-01‘,‘中國‘),(17,‘陌拜‘,‘1100‘,‘男‘,‘2014-03-03‘,‘深圳‘),(18,‘本拉登‘,‘9999‘,‘男‘,‘2003-09-09‘,‘印度‘),(19,‘奧巴馬小號‘,‘1399‘,‘男‘,‘2005-01-09‘,‘美國‘); INSERT INTO `t_product`(`id`,`name`,`price`,`description`) VALUES (6,‘飛機‘,20000000,‘預售，提貨時間暫定‘),(7,‘坦克‘,300000000,‘預售，提貨時間暫定‘),(8,‘大炮‘,500000,‘預售，提貨時間暫定‘),(9,‘航母‘,900000000,‘預售，提貨時間暫定‘); INSERT INTO `t_order`(`id`,`userId`,`createTime`,`state`) VALUES (1,18,‘2015-07-04 00:00:00‘,‘已付‘),(2,19,‘2017-01-02 00:00:00‘,‘已付‘),(3,16,‘2017-12-13 10:07:21‘,‘待付‘),(4,18,‘2017-12-05 14:44:04‘,‘報廢‘); INSERT INTO `t_orderdetail`(`id`,`productId`,`orderId`,`num`,`price`) VALUES (1,8,1,6,3000000),(2,9,2,1,900000000),(3,6,NULL,NULL,NULL);
（2）建立程序的結構，結構如下
（3）建立實體類，與數據庫中的表對應
Order.java代碼如下：
package entity; import java.util.ArrayList; import java.util.Date; import java.util.List; public class Order { private int id; private Date userId; private String createTime; private String state;
//註意這裏報錯是正常的，因為這裏之後引用了其他的實體類，它們還沒被定義，把所有的實體類建立好了以後，保存一下就可以了 private User user; //一個訂單對應一個用戶，所以在訂單中放置一個User的對象 //一個訂單可以有多件商品，這裏對應多個商品詳情，所以放置一個商品詳情集合 private List<OrderDetail> orderDetails = new ArrayList<OrderDetail>(); public Order() { super(); } public Order(int id, Date userId, String createTime, String state) { super(); this.id = id; this.userId = userId; this.createTime = createTime; this.state = state; } public int getId() { return id; } public void setId(int id) { this.id = id; } public Date getUserId() { return userId; } public void setUserId(Date userId) { this.userId = userId; } public String getCreateTime() { return createTime; } public void setCreateTime(String createTime) { this.createTime = createTime; } public String getState() { return state; } public void setState(String state) { this.state = state; } public User getUser() { return user; } public void setUser(User user) { this.user = user; } public List<OrderDetail> getOrderDetails() { return orderDetails; } public void setOrderDetails(List<OrderDetail> orderDetails) { this.orderDetails = orderDetails; } }
OrderDetail.java類的代碼如下：
package entity; public class OrderDetail { private int id; private int productId; private int orderId; private double price; private int num; private Order order; //一個訂單詳情，對應某一個訂單，所有在這裏添加一個訂單對象 private Product product; //一個訂單詳情裏面存放一種商品，對應一個商品詳情 public OrderDetail() { super(); } public OrderDetail(int id, int productId, int orderId, double price, int num) { super(); this.id = id; this.productId = productId; this.orderId = orderId; this.price = price; this.num = num; } public int getId() { return id; } public void setId(int id) { this.id = id; } public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } public int getNum() { return num; } public void setNum(int num) { this.num = num; } public Order getOrder() { return order; } public void setOrder(Order order) { this.order = order; } public int getProductId() { return productId; } public void setProductId(int productId) { this.productId = productId; } public int getOrderId() { return orderId; } public void setOrderId(int orderId) { this.orderId = orderId; } public Product getProduct() { return product; } public void setProduct(Product product) { this.product = product; } }
Product.java類代碼
package entity; public class Product { private int id; private String name; private float price; private String description; public Product() { super(); } public Product(int id, String name, float price, String description) { super(); this.id = id; this.name = name; this.price = price; this.description = description; } 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; } public String getDescription() { return description; } public void setDescription(String description) { this.description = description; } }
User.java類的代碼如下：
package entity; import java.util.ArrayList; import java.util.Date; import java.util.List; public class User { private int id; private String username; private String password; private String sex; private Date brithday; private String address; private List<Order> orders = new ArrayList<Order>(); public User() { super(); } public User(int id, String username, String password, String sex, Date brithday, String address) { super(); this.id = id; this.username = username; this.password = password; this.sex = sex; this.brithday = brithday; this.address = address; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; } public Date getBrithday() { return brithday; } public void setBrithday(Date brithday) { this.brithday = brithday; } 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; } }
（4）編寫mybatis-config.xml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"> <!-- 配置文件的根元素 --> <configuration> <!-- 環境：配置mybatis的環境 --> <environments default="development"> <!-- 可以使用多個環境變量，切換時只需修改對應default的屬性為該環境變量的id即可 --> <!-- 環境變量：可以配置多個環境變量，比如使用多數據源時，就需要配置多個環境變量 --> <environment id="development"> <!-- 事務管理 --> <transactionManager type="JDBC"></transactionManager> <!-- 數據源 --> <dataSource type="POOLED"> <property name="username" value="root" /> <property name="url" value="jdbc:mysql://localhost:3306/shop_order" /> <property name="password" value="123" /> <!-- 定義驅動連接,根據所使用的數據庫的不同進行更換，作者使用的是mySql --> <property name="driver" value="com.mysql.jdbc.Driver" /> </dataSource> </environment> </environments> </configuration>
（5）編寫SqlSessionUtil.java拿到數據庫的操作對象SqlSession，代碼如下
package common; import java.io.IOException; 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 SqlSessionUtil { public static SqlSession getSession(){ InputStream input = null; try { input = Resources.getResourceAsStream("mybatis-config.xml"); } catch (IOException e) { e.printStackTrace(); } SqlSessionFactoryBuilder builder =new SqlSessionFactoryBuilder(); SqlSessionFactory sqlSessionFactory=builder.build(input); SqlSession session=sqlSessionFactory.openSession(); return session; } }
（6）編寫dao裏面的接口，這邊學習就只寫了兩個，裏面的方法也很簡單
OrderDao.java
package dao; import java.util.List; import entity.Order; public interface OrderDao { /** * 查詢所有的訂單，並取出該訂單的用戶信息 * @return */ List<Order> queryAllOrder(); }
UserDao.java
package dao; import java.util.List; import entity.User; public interface UserDao { /** * 查詢所有用戶，並顯示每個用戶的訂單 * @return */ List<User> queryAllUser(); }
（7）編寫mapper裏面的xml文件，裏面存放數據庫語句
OrderMapper.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"> <mapper namespace="dao.OrderDao"> <select id="queryAllOrder" resultMap="Order_User"> select *,od.id as o_id,us.id as u_id from t_order as od inner join t_user as us on od.userId=us.id </select> <resultMap type="entity.Order" id="Order_User"> <id column="o_id" property="id"/> <result column="userId" property="userId"/> <result column="createTime" property="createTime"/> <result column="state" property="state"/> <association property="user" javaType="entity.User"> <id column="u_id" property="id"></id> <result column="username" property="username"/> <result column="password" property="password"/> <result column="sex" property="sex"/> <result column="brithday" property="brithday"/> <result column="address" property="address"/> </association> </resultMap> </mapper>
UserMapper.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"> <mapper namespace="dao.UserDao"> <resultMap type="entity.User" id="User_Order"> <id column="id" property="id"/> <result column="username" property="username"/> <result column="password" property="password"/> <result column="sex" property="sex"/> <result column="brithday" property="brithday"/> <result column="address" property="address"/> <collection property="orders" ofType="entity.Order"> <id column="o_id" property="id"/> <result column="userId" property="userId"/> <result column="createTime" property="createTime"/> <result column="state" property="state"/> </collection> </resultMap> <select id="queryAllUser" resultMap="User_Order"> SELECT *,o.id AS o_id FROM t_user AS u INNER JOIN t_order AS o ON u.id=o.userId </select> </mapper>
（8）在mybatis-config.xml中的<configuration>標簽裏面<environments>標簽下面添加如下映射
<mappers> <mapper resource="mapper/UserMapper.xml"/><!-- 包名。xml文件名 --> <!-- <mapper resource="mapper/OrderMapper.xml"></mapper> --> </mappers>
（9）編寫方法測試
test.java
package text; import java.util.List; import org.apache.ibatis.session.SqlSession; import common.SqlSessionUtil; import dao.OrderDao; import dao.UserDao; import entity.Order; import entity.User; public class test { public static void main(String[] args) { SqlSession session = SqlSessionUtil.getSession();//獲取數據庫操作對象SqlSession UserDao userDao = session.getMapper(dao.UserDao.class); List<User> users = userDao.queryAllUser(); for (User user : users) { System.out.println("用戶："+user.getUsername()+"的訂單"); for (Order order : user.getOrders()) { System.out.println("訂單編號："+order.getId()); System.out.println("狀態:"+order.getState()); } System.out.println(); } System.out.println("///////////////////////////////////"); System.out.println(); OrderDao orderdao = session.getMapper(dao.OrderDao.class); List<Order> orders = orderdao.queryAllOrder(); for (Order order : orders) { System.out.println("訂單編號："+order.getId()); System.out.println("購買者："+order.getUser().getUsername()); System.out.println("訂單狀態："+order.getState()); System.out.println(); } } }
使用Mybatis進行多表聯查操作