Spring源码之Resource加载源码解析(一)
2017-07-09 10:45
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Spring中资源处理架构
接口解析:
1. InputStreamSource: 支持对获取InputStreamSource流的扩展接口。
2. Resource: 用于从实际资源类型抽象出来的资源’描述’的接口
3. WritableResource :支持对其进行写入的资源的扩展接口。
4. ContextResource:从一个封闭的“上下文‘加载一个资源的扩展接口
抽象类解析:
1. AbstractResource 实现了基础的资源操作的抽象类
2. AbstractFileResolvingResource 抽象了对File资源操作的抽象类
各个类分工:
1. FileSystemResource:以文件的绝对路径方式进行访问,用来获取文件系统里面的资源。
2. ClassPathResourcee:以类路径的方式访问,可用来获取类路径下的资源文件。
3. UrlResource:以URL的方式访问,可用来代表URL对应的资源,它对URL做了一个简单的封装
4. ByteArrayResource:是针对于字节数组封装的资源,它的构建需要一个字节数组。
5. InputStreamResource:是针对于输入流封装的资源,它的构建需要一个输入流。
6. ServletContextResource:是针对于ServletContext封装的资源,用于访问ServletContext环境下的资源。ServletContextResource持有一个ServletContext的引用,其底层是通过ServletContext的getResource()方法和getResourceAsStream()方法来获取资源的。
7. VfsResource:对VFS资源的封装,提供对VFS资源访问及操作,内部则是调用VfsUtils实现的。
tip:vfs是Virtual File System虚拟文件系统,也称为虚拟文件系统开关(Virtual Filesystem Switch).是Linux档案系统对外的接口。任何要使用档案系统的程序都必须经由这层接口来使用它。(摘自百度百科…)它能一致的访问物理文件系统、jar资源、zip资源、war资源等,VFS能把这些资源一致的映射到一个目录上,访问它们就像访问物理文件资源一样,而其实这些资源不存在于物理文件系统。
8. DescriptiveResource: 包含资源的描述,但不指向实际的资源。例如:当API需要一个资源resource作为参数,但不一定用于实际读取,只用作占位符。
9. BeanDefinitionResource: 每个bean实际上也是资源的资源,而BeanDefinitionResource则是一个beanDefinition资源的封装。
资源工具类ResourceUtils
用途:用于将资源位置解析为文件系统中的文件的实用方法。主要用于Spring框架内的内部使用。/** * 该工具被下面这些类都用到啦,可以说很重要 * @see org.springframework.core.io.Resource * @see org.springframework.core.io.ClassPathResource * @see org.springframework.core.io.FileSystemResource * @see org.springframework.core.io.UrlResource * @see org.springframework.core.io.ResourceLoader **/ public abstract class ResourceUtils { //加载类路径前缀:“classpath:“ public static final String CLASSPATH_URL_PREFIX = "classpath:"; //从文件系统加载的URL前缀"file:" public static final String FILE_URL_PREFIX = "file:"; //文件系统中文件的URL协议: "file" public static final String URL_PROTOCOL_FILE = "file"; /** URL protocol for an entry from a jar file: "jar" */ public static final String URL_PROTOCOL_JAR = "jar"; /** URL protocol for an entry from a zip file: "zip" */ public static final String URL_PROTOCOL_ZIP = "zip"; /** URL protocol for an entry from a WebSphere jar file: "wsjar" */ public static final String URL_PROTOCOL_WSJAR = "wsjar"; /** URL protocol for an entry from a JBoss jar file: "vfszip" */ public static final String URL_PROTOCOL_VFSZIP = "vfszip"; /** URL protocol for a JBoss file system resource: "vfsfile" */ public static final String URL_PROTOCOL_VFSFILE = "vfsfile"; /** URL protocol for a general JBoss VFS resource: "vfs" */ public static final String URL_PROTOCOL_VFS = "vfs"; /** URL protocol for an entry from an OC4J jar file: "code-source" */ public static final String URL_PROTOCOL_CODE_SOURCE = "code-source"; //jar中的JAR URL和文件路径之间的分隔符 public static final String JAR_URL_SEPARATOR = "!/"; //返回给定资源的位置是一个网址:无论是一个特殊的“路径”伪URL或一个标准的URL。 public static boolean isUrl(String resourceLocation) { if (resourceLocation == null) { return false; } //特殊的“路径”伪URL:'classpath:' if (resourceLocation.startsWith(CLASSPATH_URL_PREFIX)) { return true; } try { //一个标准的URL new URL(resourceLocation); return true; } catch (MalformedURLException ex) { return false; } } //获取给定“资源定位”的URL public static URL getURL(String resourceLocation) throws FileNotFoundException { //非空校验 Assert.notNull(resourceLocation, "Resource location must not be null"); //特殊的“路径”伪URL:'classpath:' if (resourceLocation.startsWith(CLASSPATH_URL_PREFIX)) { //截取classpath:后面的一段 String path = resourceLocation.substring(CLASSPATH_URL_PREFIX.length()); //获取当前类加载器 ClassLoader cl = ClassUtils.getDefaultClassLoader(); //使用不同的类加载加载的根目录是不同的 URL url = (cl != null ? cl.getResource(path) : ClassLoader.getSystemResource(path)); if (url == null) { String description = "class path resource [" + path + "]"; throw new FileNotFoundException( description + " cannot be resolved to URL because it does not exist"); } return url; } try { // 直接尝试是否为“标准URL” return new URL(resourceLocation); } catch (MalformedURLException ex) { // no URL -> treat as file path try { //作为文件路径处理,再转换为URL return new File(resourceLocation).toURI().toURL(); } catch (MalformedURLException ex2) { throw new FileNotFoundException("Resource location [" + resourceLocation + "] is neither a URL not a well-formed file path"); } } } //获取给定“资源定位”的File public static File getFile(String resourceLocation) throws FileNotFoundException { //非空校验 Assert.notNull(resourceLocation, "Resource location must not be null"); //特殊的“路径”伪URL:'classpath:' if (resourceLocation.startsWith(CLASSPATH_URL_PREFIX)) { //截取classpath:后面的一段 String path = resourceLocation.substring(CLASSPATH_URL_PREFIX.length()); //生成一段描述,用于抛错提示 String description = "class path resource [" + path + "]"; //获取当前类加载器 ClassLoader cl = ClassUtils.getDefaultClassLoader(); URL url = (cl != null ? cl.getResource(path) : ClassLoader.getSystemResource(path)); if (url == null) { throw new FileNotFoundException( description + " cannot be resolved to absolute file path " + "because it does not reside in the file system"); } //获取加载文件对象 return getFile(url, description); } try { // 尝试利用URL获取File对象 return getFile(new URL(resourceLocation)); } catch (MalformedURLException ex) { //不是标准Url,则作为文件路径处理 return new File(resourceLocation); } } // 利用URL获取File对象 public static File getFile(URL resourceUrl) throws FileNotFoundException { return getFile(resourceUrl, "URL"); } // 尝试利用URL获取File对象 public static File getFile(URL resourceUrl, String description) throws FileNotFoundException { Assert.notNull(resourceUrl, "Resource URL must not be null"); if (!URL_PROTOCOL_FILE.equals(resourceUrl.getProtocol())) { throw new FileNotFoundException( description + " cannot be resolv b919 ed to absolute file path " + "because it does not reside in the file system: " + resourceUrl); } try { return new File(toURI(resourceUrl).getSchemeSpecificPart()); } catch (URISyntaxException ex) { // Fallback for URLs that are not valid URIs (should hardly ever happen). return new File(resourceUrl.getFile()); } } //通过给定URI获取文件对象 public static File getFile(URI resourceUri) throws FileNotFoundException { return getFile(resourceUri, "URI"); } //通过给定URI获取文件对象 public static File getFile(URI resourceUri, String description) throws FileNotFoundException { Assert.notNull(resourceUri, "Resource URI must not be null"); if (!URL_PROTOCOL_FILE.equals(resourceUri.getScheme())) { throw new FileNotFoundException( description + " cannot be resolved to absolute file path " + "because it does not reside in the file system: " + resourceUri); } return new File(resourceUri.getSchemeSpecificPart()); } //判断给定的URL指向文件系统中。协议包含:"file", "vfsfile" or "vfs". public static boolean isFileURL(URL url) { String protocol = url.getProtocol(); return (URL_PROTOCOL_FILE.equals(protocol) || URL_PROTOCOL_VFSFILE.equals(protocol) || URL_PROTOCOL_VFS.equals(protocol)); } //确定给定URL是否指向JAR文件中的资源。协议包含:"jar", "zip", "vfszip", "wsjar" or "code-source". public static boolean isJarURL(URL url) { String protocol = url.getProtocol(); return (URL_PROTOCOL_JAR.equals(protocol) || URL_PROTOCOL_ZIP.equals(protocol) || URL_PROTOCOL_VFSZIP.equals(protocol) || URL_PROTOCOL_WSJAR.equals(protocol) || (URL_PROTOCOL_CODE_SOURCE.equals(protocol) && url.getPath().contains(JAR_URL_SEPARATOR))); } //从给定URL中提取实际JAR文件的URL(它可以指向JAR文件中的资源或JAR文件本身) public static URL extractJarFileURL(URL jarUrl) throws MalformedURLException { //获取路径:‘jar:http://hostname/my.jar!/’ String urlFile = jarUrl.getFile(); int separatorIndex = urlFile.indexOf(JAR_URL_SEPARATOR); if (separatorIndex != -1) { //截取后为:‘jar:http://hostname/my.jar’ String jarFile = urlFile.substring(0, separatorIndex); try { return new URL(jarFile); } catch (MalformedURLException ex) { //可能在原始JAR URL中没有协议, 例如:‘jar:C:/mypath/myjar.jar’. //这通常表示JAR文件在文件系统中。 if (!jarFile.startsWith("/")) { //截取后:‘/mypath/myjar.jar’ jarFile = "/" + jarFile; } //标准URL加载:‘file:/mypath/myjar.jar’ return new URL(FILE_URL_PREFIX + jarFile); } } else { return jarUrl; } } public static URI toURI(URL url) throws URISyntaxException { return toURI(url.toString()); } public static URI toURI(String location) throws URISyntaxException { return new URI(StringUtils.replace(location, " ", "%20")); } /** * Set the {@link URLConnection#setUseCaches "useCaches"} flag on the * given connection, preferring {@code false} but leaving the * flag at {@code true} for JNLP based resources. * @param con the URLConnection to set the flag on */ public static void useCachesIfNecessary(URLConnection con) { con.setUseCaches(con.getClass().getSimpleName().startsWith("JNLP")); } }
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