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– Start

事实上，Spring 还支持自动依赖注入。

基于 XML 的自动依赖注入

package shangbo.spring.example31;public interface MessageService {	String getMessage();}

package shangbo.spring.example31;public class MessageServiceImpl implements MessageService {	public String getMessage() {		return "Hello World";	}}

package shangbo.spring.example31;public class MessagePrinter {    private MessageService service;    public void setService(MessageService service) {		this.service = service;	}	public void printMessage() {        System.out.println(service.getMessage());    }}

package shangbo.spring.example31;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;public class App {	public static void main(String[] args) {		// 实例化 Spring IoC 容器		ApplicationContext context = new ClassPathXmlApplicationContext("example.xml", MessagePrinter.class);				// 从容器中获得 MessagePrinter 的实例		MessagePrinter printer = context.getBean(MessagePrinter.class);				// 使用对象		printer.printMessage();	}}

除此之外，我们还可以全局设定自动注入方式。

基于注解的自动依赖注入

package shangbo.spring.example33;public interface MessageService {	String getMessage();}

package shangbo.spring.example33;public class MessageServiceImpl implements MessageService {	public String getMessage() {		return "Hello World";	}}

package shangbo.spring.example33;import org.springframework.beans.factory.annotation.Autowired;public class MessagePrinter {    private MessageService service;	// 自动注入    @Autowired    public void setService(MessageService service) {		this.service = service;	}	public void printMessage() {        System.out.println(service.getMessage());    }}

package shangbo.spring.example33;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;@Configurationpublic class AppConfig {	@Bean	public MessageService messageService() {		return new MessageServiceImpl();	}		@Bean	public MessagePrinter messagePrinter() {		return new MessagePrinter();	}}

package shangbo.spring.example33;import org.springframework.context.ApplicationContext;import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class App {    public static void main( String[] args )    {		// 实例化 Spring IoC 容器，也可以一次读取多个Java配置文件		ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);				// 从容器中获得 MessagePrinter 的实例		MessagePrinter printer = context.getBean(MessagePrinter.class);				// 使用对象		printer.printMessage();    }}

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