spring(四)依赖注入及bean的作用域
4、依赖注入(DI)
4.1 构造器注入
前面已经过了
4.2 Set方式注入【重点】
依赖注入:本质是set方法注入
- 依赖:bean对象的创建依赖于容器
- 注入:bean对象中的所有属性,由容器来注入
环境搭建
1、复杂类型
1、引用对象
public class Address {
private String address;
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "Address{" +
"address='" + address + '\'' +
'}';
}
}
2、实际测试对象
public class Student {
private String name;
private Address address;
private String [] books;
private List<String> hobbies;
private Map<String, String> card;
private Set<String> games;
private String wife;
private Properties info;
// 以及getter、setter、toString方法
}
3、applicationContext.xml(重点)
<?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="address" class="com.wen.pojo.Address">
<property name="address" value="天堂"/>
</bean>
<bean name="student" class="com.wen.pojo.Student">
<!--普通值注入,value-->
<property name="name" value="神仙"/>
<!--引用类型注入,ref-->
<property name="address" ref="address"/>
<!--数组注入-->
<property name="books">
<array>
<value>红楼梦</value>
<value>西游记</value>
<value>水浒传</value>
<value>三国演义</value>
</array>
</property>
<!--List-->
<property name="hobbies">
<list>
<value>敲代码</value>
<value>看电影</value>
<value>读书</value>
</list>
</property>
<!--Map-->
<property name="card">
<map>
<entry key="身份证" value="232121312"/>
<entry key="银行卡" value="293823801"/>
</map>
</property>
<!--Set-->
<property name="games">
<set>
<value>LOL</value>
<value>CS</value>
</set>
</property>
<!--null值注入-->
<property name="wife">
<null/>
</property>
<!--Properties
key = value-->
<property name="info">
<props>
<prop key="学号">20210327</prop>
<prop key="性别">男</prop>
</props>
</property>
</bean>
</beans>
4、测试类
@Test
public void test(){
ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
System.out.println(context.getBean("student", "Student.class"));
}
/*
Student{
name='神仙',
address=Address{address='天堂'},
books=[红楼梦, 西游记, 水浒传, 三国演义],
hobbies=[敲代码, 看电影, 读书],
card={身份证=232121312, 银行卡=293823801},
games=[LOL, CS], wife='null',
info={学号=20210327, 性别=男}
}
*/
4.3 p、c标签注入
p命名和c命名空间需要导入约束
Shortcut with the p-namespace
xmlns:p="http://www.springframework.org/schema/p"
Shortcut with the c-namespace
必须要有有参和无参构造器
xmlns:c="http://www.springframework.org/schema/c"
4.4 Bean作用域
1、单例模式(默认机制)
<bean id="accountService" class="com.something.DefaultAccountService"/>
<!-- the following is equivalent, though redundant (singleton scope is the default) -->
<bean id="accountService" class="com.something.DefaultAccountService" scope="singleton"/>
2.原型模式:每次从容器中get对象时,都重新创建
3.其余的request、session、application、websocket这些只能在web开发中使用