Spring 提供一个Resource接口来统一这些底层资源一致的访问,而且提供了一些便利的接口,从而能提供我们的生产力。
public interface InputStreamSource {
InputStream getInputStream() throws IOException;
}
public interface Resource extends InputStreamSource {
boolean exists();
boolean isReadable();
boolean isOpen();
URL getURL() throws IOException;
URI getURI() throws IOException;
File getFile() throws IOException;
long contentLength() throws IOException;
long lastModified() throws IOException;
Resource createRelative(String relativePath) throws IOException;
String getFilename();
String getDescription();
}
Resource接口提供了足够的抽象,足够满足我们日常使用。而且提供了很多内置Resource实现:ByteArrayResource、InputStreamResource 、FileSystemResource 、UrlResource 、ClassPathResource、ServletContextResource、VfsResource等。
实现了Resource接口的这些类都同意能够返回InputStream,因此我们可以通过这点对这些资源做统一的访问。
样例
package cn.javass.spring.chapter4;
import java.io.IOException;
import java.io.InputStream;
import org.junit.Test;
import org.springframework.core.io.ByteArrayResource;
import org.springframework.core.io.Resource;
public class ResourceTest {
@Test
public void testByteArrayResource() {
Resource resource = new ByteArrayResource("Hello World!".getBytes());
if(resource.exists()) {
dumpStream(resource);
}
}
}
private void dumpStream(Resource resource) {
InputStream is = null;
try {
//1.获取文件资源
is = resource.getInputStream();
//2.读取资源
byte[] descBytes = new byte[is.available()];
is.read(descBytes);
System.out.println(new String(descBytes));
} catch (IOException e) {
e.printStackTrace();
}
finally {
try {
//3.关闭资源
is.close();
} catch (IOException e) {
}
}
}
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。
package cn.javass.spring.chapter4.bean;
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;
}
}
<bean id="resourceBean1" class="cn.javass.spring.chapter4.bean.ResourceBean3">
<property name="resource" value="cn/javass/spring/chapter4/test1.properties"/>
</bean>
<bean id="resourceBean2" class="cn.javass.spring.chapter4.bean.ResourceBean3">
<property name="resource"
value="classpath:cn/javass/spring/chapter4/test1.properties"/>
</bean>
@Test
public void test() {
ApplicationContext ctx =
new ClassPathXmlApplicationContext("chapter4/resourceInject.xml");
ResourceBean3 resourceBean1 = ctx.getBean("resourceBean1", ResourceBean3.class);
ResourceBean3 resourceBean2 = ctx.getBean("resourceBean2", ResourceBean3.class);
Assert.assertTrue(resourceBean1.getResource() instanceof ClassPathResource);
Assert.assertTrue(resourceBean2.getResource() instanceof ClassPathResource);
}