Spring資源載入程式的getResource()範例

1. 檔案系統

Resource resource = appContext.getResource("file:c:\\testing.txt");

2. URL路徑

Resource resource = 
          appContext.getResource("url:http://www.yourdomain.com/testing.txt");

3. 類路徑

Resource resource = 
          appContext.getResource("classpath:com/yiibai/common/testing.txt");

package com.tw511.common;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.Resource;
public class App 
{
    public static void main( String[] args )
    {
    	ApplicationContext appContext = 
    	   new ClassPathXmlApplicationContext(new String[] {"If-you-have-any.xml"});

    	Resource resource = 
           appContext.getResource("classpath:com/yiibai/common/testing.txt");
    	
    try{
     	  InputStream is = resource.getInputStream();
          BufferedReader br = new BufferedReader(new InputStreamReader(is));
        	
          String line;
          while ((line = br.readLine()) != null) {
             System.out.println(line);
       	  } 
          br.close();
        	
    	}catch(IOException e){
    		e.printStackTrace();
    	}
    	
    }
}

bean資源載入器(ResourceLoaderAware)

因為 bean 沒有應用程式上下文的存取，一個bean如何存取資源？解決方法是實現 ResourceLoaderAware 介面，並為資源載入物件 setter 方法. Spring將盡的資源載入到bean。

package com.yiibai.customer.services;

import org.springframework.context.ResourceLoaderAware;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;

public class CustomerService implements ResourceLoaderAware
{
	private ResourceLoader resourceLoader;
	
	public void setResourceLoader(ResourceLoader resourceLoader) {
		this.resourceLoader = resourceLoader;
	}
		
	public Resource getResource(String location){
		return resourceLoader.getResource(location);
	}
}

Bean組態檔案

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

   <bean id="customerService" 
           class="com.yiibai.customer.services.CustomerService" />
   		
</beans>

執行它

package com.tw511.common;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.Resource;

import com.yiibai.customer.services.CustomerService;
public class App 
{
    public static void main( String[] args )
    {
    	ApplicationContext appContext = 
    	   new ClassPathXmlApplicationContext(new String[] {"Spring-Customer.xml"});
	
    	CustomerService cust = 
           (CustomerService)appContext.getBean("customerService");
    	
    	Resource resource = 
            cust.getResource("classpath:com/yiibai/common/testing.txt");
    	
    try{
          InputStream is = resource.getInputStream();
          BufferedReader br = new BufferedReader(new InputStreamReader(is));
        	
          String line;
          while ((line = br.readLine()) != null) {
     	       System.out.println(line);
          } 
          br.close();
        	
    	}catch(IOException e){
    		e.printStackTrace();
    	}
    	
    }
}

總結

如果沒有這個 getResource()方法，將需要處理不同的解決方案，如檔案物件的檔案系統資源，對URL資源的URL物件不同的資源。Spring真的很好地與這個超級通用的getResource()方法工作，它確實可以幫我們節省處理資源的時間。