02、Resource接口与资源加载

• 专栏目录

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一、资源抽象接口Resource

  Spring使用Resource装载各种资源，包括配置文件资源、国际化属性文件资源等。Resource接口位于org.springframework.core.io包下，继承interface Resource extends InputStreamSource，主要方法包含：

	/**
	 * Determine whether this resource actually exists in physical form.
	 * <p>This method performs a definitive existence check, whereas the
	 * existence of a {@code Resource} handle only guarantees a valid
	 * descriptor handle.
	 */
	boolean exists();
	
	/**
	 * Indicate whether this resource represents a handle with an open stream.
	 * If {@code true}, the InputStream cannot be read multiple times,
	 * and must be read and closed to avoid resource leaks.
	 * <p>Will be {@code false} for typical resource descriptors.
	 */
	default boolean isOpen() {
		return false;
	}
	
	/**
	 * Return a URL handle for this resource.
	 * @throws IOException if the resource cannot be resolved as URL,
	 * i.e. if the resource is not available as descriptor
	 */
	URL getURL() throws IOException;

	/**
	 * Return a File handle for this resource.
	 * @throws java.io.FileNotFoundException if the resource cannot be resolved as
	 * absolute file path, i.e. if the resource is not available in a file system
	 * @throws IOException in case of general resolution/reading failures
	 * @see #getInputStream()
	 */
	File getFile() throws IOException;

  Resource的具体实现类：

二、资源加载

1. 资源地址表达式

• Spring支持资源类型前缀：
  
  classpath:还可以成classpath*:，表示从多个模块中加载。例如：classpath*:com/demo/module*.xml表示加载com/demo/下的多个模块，而classpath:com/demo/module*.xml 表示加载com/demo/下的多个module开头，.xml结尾的配置文件。
• 资源路径匹配符
  

2. 资源加载器
   

• ResourcePatternResolver接口：继承interface ResourcePatternResolver extends ResourceLoader，支持带资源类型前缀及Ant风格的表达式。
• PathMatchingResourcePatternResolver类：实现class PathMatchingResourcePatternResolver implements ResourcePatternResolver，为Spring提供的标准实现类。
• Tips：项目打包后生成jar时，使用ResourceLoader().getResource(“classpath:<your_path>”).getFile() 可能会抛出FileNotFoundException，可以采用ResourceLoader().getResource(“classpath:<your_path>”).getInputStream() 方法读取。