一. 实体类
在《Spring：使用构造方法创建对象》一文中，Book类中的属性都是简单类型，所以可以直接使用value赋值，但是如果一个类对象中的属性包含其他类，则不能使用value进行赋值。首先添加Person类：
package io.zhangjia.entity;
public class Person {
private String name;
private Integer age;
private Book book;
public Person() {
}
public Person(String name, Integer age, Book book) {
this.name = name;
this.age = age;
this.book = book;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public Book getBook() {
return book;
}
public void setBook(Book book) {
this.book = book;
}
@Override
public String toString() {
return "Person{" +
"name='" + name + '\'' +
", age=" + age +
", book=" + book +
'}';
}
}
此时的Person中的name和age属性还是简单类型，但是Book已经却是一个单独的Java类，所以此时的bean中不能再使用value为其赋值，需要使用ref属性通过引用其他的bean的方式为其赋值，ref的值就是 <bean id=”book” 的id的值
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean id="book" class="io.zhangjia.entity.Book"> <property name="bookId" value="2"/> <property name="name" value="Spring开发"/> <property name="price" value="19.9"/> <property name="author" value="张三"/> </bean> <bean id="person" class="io.zhangjia.entity.Person"> <!-- 简单类型可以使用value完成属性的赋值，且property是单标签--> <property name="name" value="张三" /> <property name="age" value="20" /> <!-- 使用ref引用其他的bean--> <property name="book" ref="book" /> </bean> </beans>
测试类：
public class Test {
public static void main(String[] args) throws Exception {
// 初始化Spring的IOC容器
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
// 根据id获取bean
Object person = context.getBean("person");
System.out.println("person = " + person);
}
}
输出：
person = Person{name='张三', age=20, book=Book{bookId=2, name='Spring开发', author='张三', price=19.9}}
除了上述方式外，我们可以通过内部bean的方式为其赋值：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean id="person2" class="io.zhangjia.entity.Person"> <property name="name" value="王五"/> <property name="age" value="21"/> <!-- 此时的property是双标签--> <property name="book"> <!-- 内部bean--> <bean id="book" class="io.zhangjia.entity.Book"> <property name="bookId" value="2"/> <property name="name" value="Spring开发"/> <property name="price" value="19.9"/> <property name="author" value="张三"/> </bean> </property> </bean> </beans>
测试类输出：
person2 = Person{name='王五', age=21, book=Book{bookId=2, name='Spring开发', author='张三', price=19.9}}
值得注意的是，内部bean不能再被其他bean引用
二. List
我们将Person类修改为：
public class Person {
private String name;
private Integer age;
private List<Book> books;
.....
}
和上面的Book实体类一样，Person类中类型为 List<Book> 的books也不能直接使用value赋值，我们需要借助ref标签来为其赋值
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean id="book" class="io.zhangjia.entity.Book"> <property name="bookId" value="2"/> <property name="name" value="Spring开发"/> <property name="price" value="19.9"/> <property name="author" value="张三"/> </bean> <bean id="book2" class="io.zhangjia.entity.Book"> <constructor-arg name="bookId" value="1"/> <constructor-arg name="name" value="Spring实战"/> <constructor-arg name="price" value="29.9"/> <constructor-arg name="author" value="王五"/> </bean> <bean id="person" class="io.zhangjia.entity.Person"> <property name="name" value="张三"/> <property name="age" value="20"/> <property name="books"> <list> <ref bean="book"/> <ref bean="book2"/> </list> </property> </bean> </beans>
测试类输出：
person = Person{name='张三', age=20, books=[Book{bookId=2, name='Spring开发', author='张三', price=19.9}, Book{bookId=1, name='Spring实战', author='王五', price=29.9}]}
除了上述方式，我们同样可以采用内部bean的方式为其赋值：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean id="person2" class="io.zhangjia.entity.Person"> <property name="name" value="张三"/> <property name="age" value="20"/> <property name="books"> <list> <bean class="io.zhangjia.entity.Book"> <property name="bookId" value="2"/> <property name="name" value="Spring开发"/> <property name="price" value="19.9"/> <property name="author" value="张三"/> </bean> <bean class="io.zhangjia.entity.Book"> <constructor-arg name="bookId" value="1"/> <constructor-arg name="name" value="Spring实战"/> <constructor-arg name="price" value="29.9"/> <constructor-arg name="author" value="王五"/> </bean> </list> </property> </bean> </beans>
测试类输出：
person2 = Person{name='张三', age=20, books=[Book{bookId=2, name='Spring开发', author='张三', price=19.9}, Book{bookId=1, name='Spring实战', author='王五', price=29.9}]}
三. Set
Set和上面的List几乎完全一样，这里只给出相关代码，不再赘述：
Person类：
public class Person {
private String name;
private Integer age;
private Set<Book> books;
....
}
方法一：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean id="book" class="io.zhangjia.entity.Book"> <property name="bookId" value="2"/> <property name="name" value="Spring开发"/> <property name="price" value="19.9"/> <property name="author" value="张三"/> </bean> <bean id="book2" class="io.zhangjia.entity.Book"> <constructor-arg name="bookId" value="1"/> <constructor-arg name="name" value="Spring实战"/> <constructor-arg name="price" value="29.9"/> <constructor-arg name="author" value="王五"/> </bean> <bean id="person" class="io.zhangjia.entity.Person"> <property name="name" value="张三"/> <property name="age" value="20"/> <property name="books"> <set> <ref bean="book"/> <ref bean="book2"/> </set> </property> </bean> </beans>
测试类输出：
person = Person{name='张三', age=20, books=[Book{bookId=2, name='Spring开发', author='张三', price=19.9}, Book{bookId=1, name='Spring实战', author='王五', price=29.9}]}
方法二：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean id="person2" class="io.zhangjia.entity.Person"> <property name="name" value="张三"/> <property name="age" value="20"/> <property name="books"> <set> <bean class="io.zhangjia.entity.Book"> <property name="bookId" value="2"/> <property name="name" value="Spring开发"/> <property name="price" value="19.9"/> <property name="author" value="张三"/> </bean> <bean class="io.zhangjia.entity.Book"> <constructor-arg name="bookId" value="1"/> <constructor-arg name="name" value="Spring实战"/> <constructor-arg name="price" value="29.9"/> <constructor-arg name="author" value="王五"/> </bean> </set> </property> </bean> </beans>
测试类输出：
person2 = Person{name='张三', age=20, books=[Book{bookId=2, name='Spring开发', author='张三', price=19.9}, Book{bookId=1, name='Spring实战', author='王五', price=29.9}]}
三. Map
Map和List以及Set稍有不同，map标签中不再使用ref标签，而使用entry标签，其中key就是Map的key，value就是map的value
实体类：
public class Person {
private String name;
private Integer age;
private Map<String,Object> books;
....
}
applicationContext.xml：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean id="person" class="io.zhangjia.entity.Person"> <property name="name" value="张三"/> <property name="age" value="20"/> <property name="books"> <map> <entry key="bookId" value="3" /> <entry key="name" value="css开发" /> <entry key="price" value="10" /> <entry key="author" value="李四" /> </map> </property> </bean> </beans>
测试类输出：
person = Person{name='张三', age=20, books={bookId=3, name=css开发, price=10, author=李四}}
四. Properties
实体类：
public class Person {
private String name;
private Integer age;
private Properties jdbcProperties;
....
}
Properties类继承了Hashtable，所以也可以将其看做一个map，其中prop标签中的key便是map的key，而prop标签的内容，便是map的value。applicationContext.xml：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean id="person" class="io.zhangjia.entity.Person"> <property name="name" value="张三"/> <property name="age" value="20"/> <property name="jdbcProperties"> <props> <prop key="jdbc.driver">com.mysql.jdbc.Driver</prop> <prop key="jdbc.ur1">jdbc:mysql://localhost:3306/demo</prop> <prop key="jdbc.username">root</prop> <prop key="jdbc.password">zhangjia</prop> </props> </property> </bean> </beans>
测试类输出：
person = Person{name='张三', age=20, jdbcProperties={jdbc.username=root, jdbc.ur1=jdbc:mysql://localhost:3306/demo, jdbc.driver=com.mysql.jdbc.Driver, jdbc.password=zhangjia}}
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