其实一对多关联跟我们之前的一对一关联在实现上没有区别,这里只是简单举例子说明一下。
我们以客户对订单为例。
首先创建数据库
CREATE TABLE `customer` (
`id` int(11) NOT NULL auto_increment,
`name` varchar(50) default NULL,
`address` varchar(200) default NULL,
PRIMARY KEY (`id`)
)
CREATE TABLE `orders` (
`id` int(11) NOT NULL auto_increment,
`code` varchar(50) default NULL,
`customerid` int(11) default NULL,
PRIMARY KEY (`id`),
KEY `sda` (`customerid`),
CONSTRAINT `sda` FOREIGN KEY (`customerid`) REFERENCES `customer` (`id`) ON DELETE CASCADE
)
订单通过一个外建与客户表关联
实体Bean
//客户类
public class Customer {
private int id;
private String name;
private String address;
private List<Orders> orders;
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 String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public List<Orders> getOrders() {
return orders;
}
public void setOrders(List<Orders> orders) {
this.orders = orders;
}
}
//订单类
public class Orders {
private int id;
private String code;
private int customerid;
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 int getCustomerid() {
return customerid;
}
public void setCustomerid(int customerid) {
this.customerid = customerid;
}
}
下面是对应的配置文件
客户实体的配置文件
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sqlMap
PUBLIC "-//ibatis.apache.org//DTD SQL Map 2.0//EN"
"http://ibatis.apache.org/dtd/sql-map-2.dtd">
<sqlMap namespace="customer">
<typeAlias alias="customerVO" type="com.bean.onetomany.Customer"/>
<parameterMap class="customerVO" id="customerVOmp">
<parameter property="id" jdbcType="int"/>
<parameter property="name" jdbcType="varchar"/>
<parameter property="address" jdbcType="varchar"/>
</parameterMap>
<insert id="createCustomer" parameterMap="customerVOmp">
<selectKey keyProperty="id" type="post" resultClass="int">
select @@IDENTITY as value
</selectKey>
insert into customer(id,name,address) values(?,?,?)
</insert>
<resultMap class="customerVO" id="getCustomer">
<result column="id" property="id" jdbcType="int"/>
<result column="name" property="name" jdbcType="varchar"/>
<result column="address" property="address" jdbcType="varchar"/>
<result property="orders" column="id" select="orders.getOrdersByCid"/>
</resultMap>
<select id="getCustomerByName" parameterClass="java.lang.String" resultMap="getCustomer">
select * from customer where name=#value#
</select>
</sqlMap>
订单实体的配置文件
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sqlMap
PUBLIC "-//ibatis.apache.org//DTD SQL Map 2.0//EN"
"http://ibatis.apache.org/dtd/sql-map-2.dtd">
<sqlMap namespace="orders">
<typeAlias alias="ordersVO" type="com.bean.onetomany.Orders"/>
<parameterMap class="ordersVO" id="ordersVOmp">
<parameter property="id" jdbcType="int"/>
<parameter property="code" jdbcType="varchar"/>
<parameter property="customerid" jdbcType="int"/>
</parameterMap>
<insert id="createOrders" parameterMap="ordersVOmp">
<selectKey>
select @@IDENTITY as value
</selectKey>
insert into orders(id,code,customerid) values(?,?,?)
</insert>
<select id="getOrdersByCid" parameterClass="int" resultClass="ordersVO">
select * from orders where customerid = #value#
</select>
</sqlMap>
测试方法新增操作 与onetoone的新增没有本质区别
预习了一下之前的批次处理的方式
Reader reader = Resources.getResourceAsReader("SqlMapConfig.xml");
SqlMapClient sqlMap = SqlMapClientBuilder.buildSqlMapClient(reader);
Customer c1 = new Customer();
c1.setName("customer1");
c1.setAddress("c1_address1");
sqlMap.startTransaction();
sqlMap.insert("customer.createCustomer", c1);
sqlMap.startBatch();
for(int i = 0;i<10;i++){
Orders o = new Orders();
o.setCustomerid(c1.getId());
o.setCode("code_c1 "+i);
sqlMap.insert("orders.createOrders", o);
}
sqlMap.executeBatch();
sqlMap.commitTransaction();
查询方法 实现了customer 到orders 的一对多查询
Reader reader = Resources.getResourceAsReader("SqlMapConfig.xml");
SqlMapClient sqlMap = SqlMapClientBuilder.buildSqlMapClient(reader);
Customer customer = (Customer)sqlMap.queryForObject("customer.getCustomerByName", "customer1");
System.out.println(customer.getAddress());
List<Orders> orders = customer.getOrders();
for(int i = 0 ; i<orders.size();i++){
Orders o = orders.get(i);
System.out.println(o.getCode());
}
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