资源和资源加载器

changelog.md

@@ -176,4 +176,75 @@ public class PopulateBeanWithPropertyValuesTest {
 }
 ```
 
-## 资源和资源加载器
+## 资源和资源加载器
+Resource是资源的抽象和访问接口，简单写了三个实现类
+
+![](./assets/resource.png)
+
+- FileSystemResource，文件系统资源的实现类
+- ClassPathResource，classpath下资源的实现类
+- UrlResource，对java.net.URL进行资源定位的实现类
+
+ResourceLoader接口则是资源查找定位策略的抽象，DefaultResourceLoader是其默认实现类
+
+测试：
+```
+public class ResourceAndResourceLoaderTest {
+
+	@Test
+	public void testResourceLoader() throws Exception {
+		DefaultResourceLoader resourceLoader = new DefaultResourceLoader();
+
+		//加载classpath下的资源
+		Resource resource = resourceLoader.getResource("classpath:hello.txt");
+		InputStream inputStream = resource.getInputStream();
+		String content = IoUtil.readUtf8(inputStream);
+		System.out.println(content);
+		assertThat(content).isEqualTo("hello world");
+
+		//加载文件系统资源
+		resource = resourceLoader.getResource("src/test/resources/hello.txt");
+		assertThat(resource instanceof FileSystemResource).isTrue();
+		inputStream = resource.getInputStream();
+		content = IoUtil.readUtf8(inputStream);
+		System.out.println(content);
+		assertThat(content).isEqualTo("hello world");
+
+		//加载url资源
+		resource = resourceLoader.getResource("https://www.baidu.com");
+		assertThat(resource instanceof UrlResource).isTrue();
+		inputStream = resource.getInputStream();
+		content = IoUtil.readUtf8(inputStream);
+		System.out.println(content);
+	}
+}
+```
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src/main/java/org/springframework/core/io/ClassPathResource.java

@@ -3,44 +3,27 @@
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
-import java.net.URL;
 
 /**
- * 类路径下的资源
+ * classpath下的资源
  *
  * @author derekyi
  * @date 2020/11/25
  */
-public class ClassPathResource extends AbstractResource {
+public class ClassPathResource implements Resource {
 
 	private final String path;
 
-	private ClassLoader classLoader;
-
 	public ClassPathResource(String path) {
 		this.path = path;
-		this.classLoader = ClassPathResource.class.getClassLoader();
 	}
 
 	@Override
 	public InputStream getInputStream() throws IOException {
-		InputStream is = this.classLoader.getResourceAsStream(this.path);
+		InputStream is = this.getClass().getClassLoader().getResourceAsStream(this.path);
 		if (is == null) {
-			throw new FileNotFoundException("resource cannot be opened because it does not exist");
+			throw new FileNotFoundException(this.path + " cannot be opened because it does not exist");
 		}
 		return is;
 	}
-
-	@Override
-	public URL getURL() throws IOException {
-		URL url = this.classLoader.getResource(this.path);
-		if (url == null) {
-			throw new FileNotFoundException("resource cannot be resolved to URL because it does not exist");
-		}
-		return url;
-	}
-
-	public String getPath() {
-		return path;
-	}
 }

src/main/java/org/springframework/core/io/DefaultResourceLoader.java

@@ -0,0 +1,34 @@
+package org.springframework.core.io;
+
+import java.net.MalformedURLException;
+import java.net.URL;
+
+/**
+ * @author derekyi
+ * @date 2020/11/25
+ */
+public class DefaultResourceLoader implements ResourceLoader {
+
+	public static final String CLASSPATH_URL_PREFIX = "classpath:";
+
+	@Override
+	public Resource getResource(String location) {
+		if (location.startsWith(CLASSPATH_URL_PREFIX)) {
+			//classpath下的资源
+			return new ClassPathResource(location.substring(CLASSPATH_URL_PREFIX.length()));
+		} else {
+			try {
+				//尝试当成url来处理
+				URL url = new URL(location);
+				return new UrlResource(url);
+			} catch (MalformedURLException ex) {
+				//当成文件系统下的资源处理
+				String path = location;
+				if (location.startsWith("/")) {
+					path = location.substring(1);
+				}
+				return new FileSystemResource(location);
+			}
+		}
+	}
+}

src/main/java/org/springframework/core/io/FileSystemResource.java

@@ -0,0 +1,33 @@
+package org.springframework.core.io;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.NoSuchFileException;
+import java.nio.file.Path;
+
+/**
+ * @author derekyi
+ * @date 2020/11/25
+ */
+public class FileSystemResource implements Resource {
+
+	private final String filePath;
+
+	public FileSystemResource(String filePath) {
+		this.filePath = filePath;
+	}
+
+	@Override
+	public InputStream getInputStream() throws IOException {
+
+		try {
+			Path path = new File(this.filePath).toPath();
+			return Files.newInputStream(path);
+		} catch (NoSuchFileException ex) {
+			throw new FileNotFoundException(ex.getMessage());
+		}
+	}
+}

src/main/java/org/springframework/core/io/Resource.java

@@ -1,23 +1,16 @@
 package org.springframework.core.io;
 
-import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
-import java.net.URL;
 
 /**
- * 资源的抽象接口
+ * 资源的抽象和访问接口
  *
  * @author derekyi
  * @date 2020/11/25
  */
 public interface Resource {
 
-	boolean exists();
-
-	File getFile() throws IOException;
-
 	InputStream getInputStream() throws IOException;
 
-	URL getURL() throws IOException;
 }

src/main/java/org/springframework/core/io/ResourceLoader.java

@@ -0,0 +1,12 @@
+package org.springframework.core.io;
+
+/**
+ * 资源加载器接口
+ *
+ * @author derekyi
+ * @date 2020/11/25
+ */
+public interface ResourceLoader {
+
+	Resource getResource(String location);
+}

src/main/java/org/springframework/core/io/UrlResource.java

@@ -0,0 +1,29 @@
+package org.springframework.core.io;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.net.URLConnection;
+
+/**
+ * @author derekyi
+ * @date 2020/11/25
+ */
+public class UrlResource implements Resource {
+
+	private final URL url;
+
+	public UrlResource(URL url) {
+		this.url = url;
+	}
+
+	@Override
+	public InputStream getInputStream() throws IOException {
+		URLConnection con = this.url.openConnection();
+		try {
+			return con.getInputStream();
+		} catch (IOException ex) {
+			throw ex;
+		}
+	}
+}

src/test/java/org/springframework/test/ioc/ResourceAndResourceLoaderTest.java

@@ -0,0 +1,43 @@
+package org.springframework.test.ioc;
+
+import cn.hutool.core.io.IoUtil;
+import org.junit.Test;
+import org.springframework.core.io.*;
+
+import java.io.InputStream;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author derekyi
+ * @date 2020/11/25
+ */
+public class ResourceAndResourceLoaderTest {
+
+	@Test
+	public void testResourceLoader() throws Exception {
+		DefaultResourceLoader resourceLoader = new DefaultResourceLoader();
+
+		//加载classpath下的资源
+		Resource resource = resourceLoader.getResource("classpath:hello.txt");
+		InputStream inputStream = resource.getInputStream();
+		String content = IoUtil.readUtf8(inputStream);
+		System.out.println(content);
+		assertThat(content).isEqualTo("hello world");
+
+		//加载文件系统资源
+		resource = resourceLoader.getResource("src/test/resources/hello.txt");
+		assertThat(resource instanceof FileSystemResource).isTrue();
+		inputStream = resource.getInputStream();
+		content = IoUtil.readUtf8(inputStream);
+		System.out.println(content);
+		assertThat(content).isEqualTo("hello world");
+
+		//加载url资源
+		resource = resourceLoader.getResource("https://www.baidu.com");
+		assertThat(resource instanceof UrlResource).isTrue();
+		inputStream = resource.getInputStream();
+		content = IoUtil.readUtf8(inputStream);
+		System.out.println(content);
+	}
+}

src/test/resources/hello.txt

@@ -0,0 +1 @@
+hello world