Spring-Context的注解实现依赖注入功能

使用Spring-Context的注解实现依赖注入功能.

Demo要点：

本例子中主要使用Annotation功能来实现对MoviceService的注入。我们将Cinema.java的头部标注为@Component说明该类交由Spring托管。而Cinema.java中的属性MoviceService标注为@Autowired，则Spring在初始化Cinema类时会从Application Context中找到类型为MovieService的Bean，并赋值给Cinema。在Application.java中我们声明了一个类型为MovieService的Bean。并且标注Application.java为@Configuration,这是告诉Spring在Application.java中定义了一个或多个@Bean方法，让Spring容器可以在运行时生成这些Bean。@ComponentScan则会让Spring容器自动扫描当前package下的标有@Component的class，这些class都将由Spring托管。此时 就要注意Application.java需要在一个较为上层的包，不然会报错找不到类。

项目结构：

Pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" 
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"    
    
    >
    <modelVersion>4.0.0</modelVersion>
    <groupId>MarkDemo</groupId>
    <artifactId>MarkDemo.SpringContext</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <build />
    
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.1.1.RELEASE</version>
        </dependency>
    </dependencies>
    
</project>

MovieService.java

package MarkDemo.service;


public interface MovieService {

    String getMovieName();
}

DefaultMovieService.java

package MarkDemo.service;

public class DefaultMovieService implements MovieService {

    public String getMovieName() {
        return "INTO THE WILD, HELLO SPRING CONTEXT";
    }
}

Cinema.java

package MarkDemo.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;

@Component
public class Cinema {
    
    @Autowired
    private MovieService movieService;

    public void printMovieName() {
        System.out.println(movieService.getMovieName());
    }

    public MovieService getMovieService() {
        return movieService;
    }

    public void setMovieService(MovieService movieService) {
        this.movieService = movieService;
    }
    
}

Application.java

package MarkDemo.service;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan
public class Application {

    @Bean
    public MovieService getMovieService() {
        return new DefaultMovieService();
    }

    public static void main(String[] args) throws Exception {
        // TODO Auto-generated method stub
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(Application.class);
        Cinema cinema = applicationContext.getBean(Cinema.class);
        cinema.printMovieName();
        applicationContext.close();

    }

}

没有annotation支持之前则需要applicationContext.xml文件。

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:p="http://www.springframework.org/schema/p" xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
               http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

    <bean id="movieService" class="MarkDemo.service.DefaultMovieService"></bean>

    <bean id="cinema" class="MarkDemo.service.Cinema">
        <property name="movieService" ref="movieService"></property>
    </bean>

</beans>

application.java的main方法

public static void main(String[] args) throws Exception {
        // TODO Auto-generated method stub
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(Application.class);
        Cinema cinema = applicationContext.getBean(Cinema.class);
        cinema.printMovieName();
        applicationContext.close();
        
        //不使用annotation，使用配置文件。
        System.out.println(ClassLoader.getSystemResource(""));
        @SuppressWarnings("resource")
        ApplicationContext appContext= new ClassPathXmlApplicationContext("classpath:/MarkDemo/service/applicationContext.xml");
        Cinema cinema1=appContext.getBean("cinema",MarkDemo.service.Cinema.class);
        cinema1.printMovieName();    
        
    }

参考文章：http://www.2cto.com/kf/201403/284656.html