Spring依赖注入之Resource和Component

Resource是j2ee的内容，如果要使用注解@Resource，必须引入jar文件common-annotations.jar

@Resource注解在set方法上，默认是通过ByType形式进行注入

class代码如下：

@Resource2     public void setBookDAO(BookDAO bookDAO) {
        System.out.println("******************setBookDAO");
        this.bookDAO = bookDAO;
        System.out.println(this.bookDAO.getClass().toString());        
    }

xml文件如下：

<bean id="BookDAOImpl" class="com.test.dao.impl.BookDAOImpl">
    
  </bean>

@Resource注解在set方法上，也可以通过ByName指定bean

class代码如下：

@Resource(name="u")
    public void setBookDAO(BookDAO bookDAO) {
        System.out.println("******************setBookDAO");
        this.bookDAO = bookDAO;
        System.out.println(this.bookDAO.getClass().toString());        
    }

xml文件如下：

<bean id="u" class="com.test.dao.impl.BookDAOImpl">   
  </bean>

@Component是Spring本身包含的功能，无需引入其它额外的jar文件
使用注解@Component之前，xml的头必须加上如下信息：

<!-- 扫描“com.test”包下面的所有class文件，如果含有注解@Componeent的class类创建实例 -->
       <context:component-scan base-package="com.test" />

@Component是标记是class类上面，class代码如下：

 

package com.test.service.impl;

import java.util.ArrayList;

import javax.annotation.Resource;

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


import com.test.dao.BookDAO;
import com.test.domain.Book;
import com.test.service.BookService;

@Component("bookService")
public class BookServiceImpl implements BookService{
    
    private BookDAO bookDAO;    
    public BookServiceImpl(){
        System.out.println("BookServiceImpl init!");
    }

    public BookDAO getBookDAO() {
        return bookDAO;
    }
    
    @Resource(name="BookDAOImpl")
    public void setBookDAO(BookDAO bookDAO) {
        System.out.println("******************setBookDAO");
        this.bookDAO = bookDAO;
        System.out.println(this.bookDAO.getClass().toString());        
    }

    public ArrayList<Book> getBooks() {
        // TODO Auto-generated method stub
        return null;
    }

    public void add(Book book) {
        System.out.println(bookDAO.getClass().toString());
        bookDAO.saveBook(book);

        
    }            

}

@Component("bookService")是指定名字"bookService"，也就等同于在xml配置一个bean,如：

<bean id="bookService" class="com.test.service.impl.BookServiceImpl">   
</bean>

可以通过context.getBean("bookService")获取到该实例
也可以通过@Resource(name="bookSercie")注解在set方法上，注入到变量中

下面代码是将BookDAOImpl类实例化，key变量为bookDAO

package com.test.dao.impl;

import java.util.List;
import org.springframework.stereotype.Component;
import com.test.dao.BookDAO;
import com.test.domain.Book;

@Component("bookDAO")
public class BookDAOImpl implements BookDAO {
    
    public void saveBook(Book book) {        
        System.out.println("save book success!");        
    }
    
    public BookDAOImpl(){
        System.out.println("BookDAOImpl inti!");
    }
    
    public List<Book> getBookList() {        
        return null;
    }
}

下面的代码是通@Resource，指定name为bookDAO的实例类通过set方法注入到bookDAO变量中　　

package com.test.service.impl;

import java.util.ArrayList;
import javax.annotation.Resource;
import org.springframework.stereotype.Component;
import com.test.dao.BookDAO;
import com.test.domain.Book;
import com.test.service.BookService;

@Component("bookService")
public class BookServiceImpl implements BookService{    
    private BookDAO bookDAO;    
    public BookServiceImpl(){
        System.out.println("BookServiceImpl init!");
    }

    public BookDAO getBookDAO() {
        return bookDAO;
    }
    
    @Resource(name="bookDAO")
    public void setBookDAO(BookDAO bookDAO) {
        System.out.println("******************setBookDAO");
        this.bookDAO = bookDAO;
        System.out.println(this.bookDAO.getClass().toString());        
    }

    public ArrayList<Book> getBooks() {
        return null;
    }

    public void add(Book book) {
        System.out.println(bookDAO.getClass().toString());
        bookDAO.saveBook(book);        
    }            
}