开涛spring3(4.3) - 资源之 4.3 访问Resource

4.3.1 ResourceLoader接口

ResourceLoader接口用于返回Resource对象；其实现可以看作是一个生产Resource的工厂类。

public interface ResourceLoader {
       Resource getResource(String location);
       ClassLoader getClassLoader();
}

getResource接口用于根据提供的location参数返回相应的Resource对象；而getClassLoader则返回加载这些Resource的ClassLoader。

Spring提供了一个适用于所有环境的DefaultResourceLoader实现，可以返回ClassPathResource、 UrlResource；还提供一个用于web环境的ServletContextResourceLoader，它继承了 DefaultResourceLoader的所有功能，又额外提供了获取ServletContextResource的支持。

ResourceLoader在进行加载资源时需要使用前缀来指定需要加载：“classpath:path”表示返回 ClasspathResource，“http://path”和“file:path”表示返回UrlResource资源，如果不加前缀则需要根据当前上下文来决定，DefaultResourceLoader默认实现可以加载classpath资源，如代码所示

package lqy.springh4_3;
 
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
 
import org.junit.Assert;
import org.junit.Test;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.core.io.FileSystemResource;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.core.io.UrlResource;
 
public class ResourceTest  {
 
    public static void main(String[] args) throws IOException {
 
    }
 
    @Test
    public void testResourceLoad1() {
        ResourceLoader loader = new DefaultResourceLoader(); 
 
        Resource resource = loader.getResource("classpath:lqy/springh4_3/test1.txt");
        //验证返回的是ClassPathResource
        Assert.assertEquals(ClassPathResource.class, resource.getClass());
    }
    @Test
    public void testResourceLoad2() {
        ResourceLoader loader = new DefaultResourceLoader(); 
 
        Resource resource2 = loader.getResource("file:lqy/springh4_3/test1.txt");
        //验证返回的是ClassPathResource
        Assert.assertEquals(UrlResource.class, resource2.getClass()); 
 
    }
    @Test
    public void testResourceLoad3() {
        ResourceLoader loader = new DefaultResourceLoader(); 
 
        Resource resource3 = loader.getResource("lqy/springh4_3/test1.txt");
        //验证返默认可以加载ClasspathResource
        Assert.assertTrue(resource3 instanceof ClassPathResource);
    } 
 
}

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" 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对于目前所有ApplicationContext都实现了ResourceLoader，因此可以使用其来加载资源。

ClassPathXmlApplicationContext：不指定前缀将返回默认的ClassPathResource资源，否则将根据前缀来加载资源；

FileSystemXmlApplicationContext：不指定前缀将返回FileSystemResource，否则将根据前缀来加载资源；

WebApplicationContext：不指定前缀将返回ServletContextResource，否则将根据前缀来加载资源；

其他：不指定前缀根据当前上下文返回Resource实现，否则将根据前缀来加载资源。

4.3.2 ResourceLoaderAware接口

ResourceLoaderAware是一个标记接口，用于通过ApplicationContext上下文注入ResourceLoader。

public interface ResourceLoaderAware {
   void setResourceLoader(ResourceLoader resourceLoader);
}

1）首先准备测试Bean，我们的测试Bean还简单只需实现ResourceLoaderAware接口，然后通过回调将ResourceLoader保存下来就可以了：

package lqy.springh4_3;
 
import org.springframework.context.ResourceLoaderAware;
import org.springframework.core.io.ResourceLoader;
public class ResourceBean implements ResourceLoaderAware {  
 
    private ResourceLoader resourceLoader; 
 
    public void setResourceLoader(ResourceLoader resourceLoader) {
        this.resourceLoader = resourceLoader;
    }  
    public ResourceLoader getResourceLoader() {
        return resourceLoader;
    }
}

2）配置Bean定义

 <bean class="lqy.springh4_3.ResourceBean"/>

3）测试

package lqy.springh4_3;
 
import java.io.IOException;
 
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.ResourceLoader;
 
public class ResourceTest  {
 
    public static void main(String[] args) throws IOException {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("classpath:lqy/springh4_3/springh4_3.xml");
        ResourceBean resourceBean = ctx.getBean(ResourceBean.class);
        ResourceLoader loader = resourceBean.getResourceLoader();
        System.out.print(loader instanceof ApplicationContext);
 
    }
}

aaarticlea/png;base64,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" alt="" />

注意此处“loader instanceof ApplicationContext”，说明了ApplicationContext就是个ResoureLoader。

由于上述实现回调接口注入ResourceLoader的方式属于侵入式，所以不推荐上述方法，可以采用更好的自动注入方式，如“byType”和“constructor”，此处就不演示了。

4.3.3 注入Resource

通过回调或注入方式注入“ResourceLoader”，然后再通过“ResourceLoader”再来加载需要的资源对于只需要加载某个固定的资源是不是很麻烦，有没有更好的方法类似于前边实例中注入“java.io.File”类似方式呢？

Spring提供了一个PropertyEditor “ResourceEditor”用于在注入的字符串和Resource之间进行转换。因此可以使用注入方式注入Resource。

ResourceEditor完全使用ApplicationContext根据注入的路径字符串获取相应的Resource，说白了还是自己做还是容器帮你做的问题。

接下让我们看下示例：

1）准备Bean：

package lqy.springh4_3;
 
import org.springframework.core.io.Resource;
public class ResourceBean3 {
    private Resource resource;
    public Resource getResource() {
        return resource;
    }
    public void setResource(Resource resource) {
        this.resource = resource;
    }
}

2）准备配置文件

 <bean id="resourceBean1" class="lqy.springh4_3.ResourceBean3">
   <property name="resource" value="lqy/springh4_3/test1.properties"/>
</bean>
<bean id="resourceBean2" class="lqy.springh4_3.ResourceBean3">
<property name="resource"  value="classpath:lqy/springh4_3/test1.properties"/>
</bean>

注意此处“resourceBean1”注入的路径没有前缀表示根据使用的ApplicationContext实现进行选择Resource实现。

3）让我们来看下测试代码

package lqy.springh4_3;
 
import java.io.IOException;
 
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
 
public class ResourceTest  {
 
    public static void main(String[] args) throws IOException {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("classpath:lqy/springh4_3/springh4_3.xml");
 
        ResourceBean3 resourceBean1 = ctx.getBean("resourceBean1", ResourceBean3.class);
        ResourceBean3 resourceBean2 = ctx.getBean("resourceBean2", ResourceBean3.class); 
 
        System.out.println(resourceBean1.getResource() instanceof ClassPathResource);
        System.out.println(resourceBean2.getResource() instanceof ClassPathResource );
 
    }
}

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接下来一节让我们深入ApplicationContext对各种Resource的支持，及如何使用更便利的资源加载方式。