Use annotations instead of Spring configuration files

Use annotations instead of Spring configuration files Specific steps

Create a WEB project - import package - introduce a new namespace (constraint) for the main configuration file - enable the use of annotation proxy configuration file - use annotations in the class to complete the configuration

1 guide package

springsource.org.aopalliance-1.0.0.jar
springsource.org.apache.commons.logging-1.1.1.jar
springsource.org.apache.log4j-1.2.15.jar
springsource.org.aspectj.weaver-1.6.8.RELEASE.jar
spring-aop-4.2.4.RELEASE.jar
spring-aspects-4.2.4.RELEASE.jar
spring-beans-4.2.4.RELEASE.jar
spring-context-4.2.4.RELEASE.jar
spring-core-4.2.4.RELEASE.jar
spring-expression-4.2.4.RELEASE.jar
spring-test-4.2.4.RELEASE.jar

2 Introduce a new namespace (constraint)-context constraint to the main configuration file

3 Enable the use of annotation proxy configuration files

<!-- Specifies to scan annotations in all classes under the com.hciot.bean package. Note: When scanning the package, it will scan all descendant packages under the specified report -->

<context:component-scan base-package="com.hciot.bean"></context:component-scan>

4 Use annotations in the class to complete the configuration

4.1 Register the object with the container

// Equivalent to <bean name="user" class="com.hciot.bean.User"></bean> in the configuration file
  @Component("user")
//@Service("user")		//service层
//@Controller("user")		//web层
//@Repository("user")		//Dao层

Test result User [name=null, age=null, car=null]

4.2 Modifying the scope of an object

 //Specify the scope of the object
    //@Scope(scopeName="prototype")
      @Scope(scopeName="singleton")

4.3 value type injection

//Inject the property value into the object
	@Value("tom")
	public void setName(String name) {
		this.name = name;
	}
	@Value("28")
	public void setAge(Integer age) {
		this.age = age;
	}

Test result User [name=tom, age=28, car=null]

4.4 reference type injection

Inject the car object into the container

package com.hciot.bean;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component("car")
public class Car {
	private String name;
	private String color;
	
	@Value("BMW")
	public void setName(String name) {
		this.name = name;
	}
	@Value("Yellow")
	public void setColor(String color) {
		this.color = color;
	}
	@Override
	public String toString() {
		return "Car [name=" + name + ", color=" + color + "]";
	}
}

@Autowired // Automatic assembly, but when there are multiple objects of the same type, it will not be possible to choose which object to inject
     private Car car;

Test result User [name=tom, age=28, car=Car [name=BMW, color=yellow]]

	@Autowired
	@Qualifier("car2")//Use the Qualifier annotation to tell the spring container which object to autowire
	private Car car;

Test result User [name=tom, age=28, car=Car [name=Benz, color=yellow]]

	@Resource(name="car2") //Manual injection, specify which object to inject
	private Car car;

4.5 Initialization|Destruction method

@PostConstruct//Called after the object is created
     public void init(){
      System.out.println("I am the initialization method");
     }

@PreDestroy//Called before the object is destroyed

public void destroy(){ System.out.println("Destruction method"); }

I am the initialization method
    User [name=tom, age=28, car=Car [name=Benz, color=yellow]]
    Destruction method

appendix

test code

package com.hciot.a_annotation;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.hciot.bean.User;

public class Demo {
	@Test
	public void fun1(){
		//1. Create a container object
		ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
		//ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");

		//2. Ask the container for the user object
		User u = (User) ac.getBean("user");
		User u2 = (User) ac.getBean("user");
		User u3 = (User) ac.getBean("user");
		//3. Print the user object
		System.out.println(u2);
		ac.close();
		//System.out.println(u2==u3);
	}
}

User object

package com.hciot.bean;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import javax.annotation.Resource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Controller;
import org.springframework.stereotype.Repository;
import org.springframework.stereotype.Service;

// Equivalent to <bean name="user" class="com.hciot.bean.User"></bean> in the configuration file
@Component("user")
//@Service("user")		//service层
//@Controller("user")		//web层
//@Repository("user")		//Dao层
//Specify the scope of the object
//@Scope(scopeName="prototype")
@Scope(scopeName="singleton")
public class User {
		private String name;
		private Integer age;
		//@Autowired
		//@Qualifier("car2")//Use the Qualifier annotation to tell the spring container which object to autowire
		@Resource(name="car2")
		private Car car;
		
		public String getName() {
			return name;
		}
		public Integer getAge() {
			return age;
		}
		//Inject the property value into the object
		@Value("tom")
		public void setName(String name) {
			this.name = name;
		}
		@Value("28")
		public void setAge(Integer age) {
			this.age = age;
		}
		
		public Car getCar() {
			return car;
		}
		public void setCar(Car car) {
			this.car = car;
		}
		
		@PostConstruct//Called after the object is created
		public void init(){
			System.out.println("I am the initialization method");
		}
		@PreDestroy//Called before the object is destroyed
		public void destroy(){
			System.out.println("Destruction method");
		}
		
		@Override
		public String toString() {
			return "User [name=" + name + ", age=" + age + ", car=" + car + "]";
		}
}

configuration file

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.2.xsd ">

<!-- Specifies to scan annotations in all classes under the com.hciot.bean package. Note: When scanning the package, it will scan all descendant packages under the specified report -->

<context:component-scan base-package="com.hciot.bean"></context:component-scan>

<bean name="car2" class="com.hciot.bean.Car">
	<property name="name" value="奔驰"></property>
	<property name="color" value="黄色"></property>
</bean>
</beans>

Use annotations instead of Spring configuration files

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