Spring的两种常见的注入
spring有多种依赖注入的形式，下面仅介绍spring通过xml进行IOC配置的方式：
1, Set注入
需要配置的bean.xml文件
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN" "http://www.springframework.org/dtd/spring-beans-2.0.dtd"> <beans> <description>Spring quick start</description> <bean id="student" class="org.heinrich.action.Student"> <property name="user" ref="user"> </property> </bean> <bean id="user" class="org.heinrich.action.User"></bean> </beans>
两个实体类 Student , User
package org.heinrich.action;
public class User {
public void read(){
System.out.println("I am reading Book of Thinking Java");
}
}
package org.heinrich.action;
public class Student {
private User user;
public void testDi(){
user.read();
}
public void setUser(User user) {
this.user = user;
}
}
测试SpringTest类
package org.heinrich.action;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class SpringTest {
public static void main(String[] args) {
ApplicationContext ctx = new ClassPathXmlApplicationContext("bean.xml");
Student student = (Student)ctx.getBean("student");
student.testDi();
}
}
显示的结果
I am reading Book of Thinking Java
其中bean.xml还可以配置成
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN" "http://www.springframework.org/dtd/spring-beans-2.0.dtd"> <beans> <description>Spring quick start</description> <bean id="student" class="org.heinrich.action.Student"> <property name="user"> 重点: <bean id="user" class="org.heinrich.action.User"></bean> </property> </bean> </beans>
2, 构造器注入
主要代码Student类需要给一个构造方法,参数是需要注入的类型
package org.heinrich.action;
public class Student {
private User user;
public Student(User user) {
super();
this.user = user;
}
public void testDi() {
user.read();
}
}
然后配置bean.xml
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN" "http://www.springframework.org/dtd/spring-beans-2.0.dtd"> <beans> <description>Spring quick start</description> <bean id="student" class="org.heinrich.action.Student"> <constructor-arg ref="user"/> </bean> <bean id="user" class="org.heinrich.action.User"></bean> </beans>
bean.xml还有另外一个配置方式
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN" "http://www.springframework.org/dtd/spring-beans-2.0.dtd"> <beans> <description>Spring quick start</description> <bean id="student" class="org.heinrich.action.Student"> <constructor-arg> <bean id="user" class="org.heinrich.action.User"></bean> </constructor-arg> </bean> </beans>
测试结果
I am reading Book of Thinking Java