org.springframework.util

## Class ResourceUtils

- java.lang.Object
- - org.springframework.util.ResourceUtils

-     public abstract class ResourceUtils
      extends Object

  Utility methods for resolving resource locations to files in the file system. Mainly for internal use within the framework.

  Consider using Spring's Resource abstraction in the core package for handling all kinds of file resources in a uniform manner. `ResourceLoader`'s `getResource` method can resolve any location to a `Resource` object, which in turn allows to obtain a `java.io.File` in the file system through its `getFile()` method.

  The main reason for these utility methods for resource location handling is to support `Log4jConfigurer`, which must be able to resolve resource locations before the logging system has been initialized. Spring' Resource abstraction in the core package, on the other hand, already expects the logging system to be available.

  Since:
    1.1.5
  Author:
    Juergen Hoeller
  See Also:
    `Resource`, `ClassPathResource`, `FileSystemResource`, `UrlResource`, `ResourceLoader`

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static String` | `CLASSPATH_URL_PREFIX` Pseudo URL prefix for loading from the class path: "classpath:"
    `static String` | `FILE_URL_PREFIX` URL prefix for loading from the file system: "file:"
    `static String` | `JAR_URL_SEPARATOR` Separator between JAR URL and file path within the JAR
    `static String` | `URL_PROTOCOL_CODE_SOURCE` URL protocol for an entry from an OC4J jar file: "code-source"
    `static String` | `URL_PROTOCOL_FILE` URL protocol for a file in the file system: "file"
    `static String` | `URL_PROTOCOL_JAR` URL protocol for an entry from a jar file: "jar"
    `static String` | `URL_PROTOCOL_VFS` URL protocol for a JBoss VFS resource: "vfs"
    `static String` | `URL_PROTOCOL_VFSZIP` URL protocol for an entry from a JBoss jar file: "vfszip"
    `static String` | `URL_PROTOCOL_WSJAR` URL protocol for an entry from a WebSphere jar file: "wsjar"
    `static String` | `URL_PROTOCOL_ZIP` URL protocol for an entry from a zip file: "zip"

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `ResourceUtils()`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `static URL` | `extractJarFileURL(URL jarUrl)` Extract the URL for the actual jar file from the given URL (which may point to a resource in a jar file or to a jar file itself).
    `static File` | `getFile(String resourceLocation)` Resolve the given resource location to a `java.io.File`, i.e.
    `static File` | `getFile(URI resourceUri)` Resolve the given resource URI to a `java.io.File`, i.e.
    `static File` | `getFile(URI resourceUri, String description)` Resolve the given resource URI to a `java.io.File`, i.e.
    `static File` | `getFile(URL resourceUrl)` Resolve the given resource URL to a `java.io.File`, i.e.
    `static File` | `getFile(URL resourceUrl, String description)` Resolve the given resource URL to a `java.io.File`, i.e.
    `static URL` | `getURL(String resourceLocation)` Resolve the given resource location to a `java.net.URL`.
    `static boolean` | `isFileURL(URL url)` Determine whether the given URL points to a resource in the file system, that is, has protocol "file" or "vfs".
    `static boolean` | `isJarURL(URL url)` Determine whether the given URL points to a resource in a jar file, that is, has protocol "jar", "zip", "wsjar" or "code-source".
    `static boolean` | `isUrl(String resourceLocation)` Return whether the given resource location is a URL: either a special "classpath" pseudo URL or a standard URL.
    `static URI` | `toURI(String location)` Create a URI instance for the given location String, replacing spaces with "%20" quotes first.
    `static URI` | `toURI(URL url)` Create a URI instance for the given URL, replacing spaces with "%20" quotes first.
    `static void` | `useCachesIfNecessary(URLConnection con)` Set the `"useCaches"` flag on the given connection, preferring `false` but leaving the flag at `true` for JNLP based resources.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### CLASSPATH_URL_PREFIX

          public static final String CLASSPATH_URL_PREFIX

      Pseudo URL prefix for loading from the class path: "classpath:"
      See Also:
        Constant Field Values

    - #### FILE_URL_PREFIX

          public static final String FILE_URL_PREFIX

      URL prefix for loading from the file system: "file:"
      See Also:
        Constant Field Values

    - #### URL_PROTOCOL_FILE

          public static final String URL_PROTOCOL_FILE

      URL protocol for a file in the file system: "file"
      See Also:
        Constant Field Values

    - #### URL_PROTOCOL_JAR

          public static final String URL_PROTOCOL_JAR

      URL protocol for an entry from a jar file: "jar"
      See Also:
        Constant Field Values

    - #### URL_PROTOCOL_ZIP

          public static final String URL_PROTOCOL_ZIP

      URL protocol for an entry from a zip file: "zip"
      See Also:
        Constant Field Values

    - #### URL_PROTOCOL_VFSZIP

          public static final String URL_PROTOCOL_VFSZIP

      URL protocol for an entry from a JBoss jar file: "vfszip"
      See Also:
        Constant Field Values

    - #### URL_PROTOCOL_VFS

          public static final String URL_PROTOCOL_VFS

      URL protocol for a JBoss VFS resource: "vfs"
      See Also:
        Constant Field Values

    - #### URL_PROTOCOL_WSJAR

          public static final String URL_PROTOCOL_WSJAR

      URL protocol for an entry from a WebSphere jar file: "wsjar"
      See Also:
        Constant Field Values

    - #### URL_PROTOCOL_CODE_SOURCE

          public static final String URL_PROTOCOL_CODE_SOURCE

      URL protocol for an entry from an OC4J jar file: "code-source"
      See Also:
        Constant Field Values

    - #### JAR_URL_SEPARATOR

          public static final String JAR_URL_SEPARATOR

      Separator between JAR URL and file path within the JAR
      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### ResourceUtils

          public ResourceUtils()

  - ### Method Detail

    - #### isUrl

          public static boolean isUrl(String resourceLocation)

      Return whether the given resource location is a URL: either a special "classpath" pseudo URL or a standard URL.
      Parameters:
        `resourceLocation` - the location String to check
      Returns:
        whether the location qualifies as a URL
      See Also:
        `CLASSPATH_URL_PREFIX`, `URL`

    - #### getURL

          public static URL getURL(String resourceLocation)
                            throws FileNotFoundException

      Resolve the given resource location to a `java.net.URL`.

      Does not check whether the URL actually exists; simply returns the URL that the given location would correspond to.

      Parameters:
        `resourceLocation` - the resource location to resolve: either a "classpath:" pseudo URL, a "file:" URL, or a plain file path
      Returns:
        a corresponding URL object
      Throws:
        `FileNotFoundException` - if the resource cannot be resolved to a URL

    - #### getFile

          public static File getFile(String resourceLocation)
                              throws FileNotFoundException

      Resolve the given resource location to a `java.io.File`, i.e. to a file in the file system.

      Does not check whether the fil actually exists; simply returns the File that the given location would correspond to.

      Parameters:
        `resourceLocation` - the resource location to resolve: either a "classpath:" pseudo URL, a "file:" URL, or a plain file path
      Returns:
        a corresponding File object
      Throws:
        `FileNotFoundException` - if the resource cannot be resolved to a file in the file system

    - #### getFile

          public static File getFile(URL resourceUrl)
                              throws FileNotFoundException

      Resolve the given resource URL to a `java.io.File`, i.e. to a file in the file system.
      Parameters:
        `resourceUrl` - the resource URL to resolve
      Returns:
        a corresponding File object
      Throws:
        `FileNotFoundException` - if the URL cannot be resolved to a file in the file system

    - #### getFile

          public static File getFile(URL resourceUrl,
                     String description)
                              throws FileNotFoundException

      Resolve the given resource URL to a `java.io.File`, i.e. to a file in the file system.
      Parameters:
        `resourceUrl` - the resource URL to resolve
        `description` - a description of the original resource that the URL was created for (for example, a class path location)
      Returns:
        a corresponding File object
      Throws:
        `FileNotFoundException` - if the URL cannot be resolved to a file in the file system

    - #### getFile

          public static File getFile(URI resourceUri)
                              throws FileNotFoundException

      Resolve the given resource URI to a `java.io.File`, i.e. to a file in the file system.
      Parameters:
        `resourceUri` - the resource URI to resolve
      Returns:
        a corresponding File object
      Throws:
        `FileNotFoundException` - if the URL cannot be resolved to a file in the file system

    - #### getFile

          public static File getFile(URI resourceUri,
                     String description)
                              throws FileNotFoundException

      Resolve the given resource URI to a `java.io.File`, i.e. to a file in the file system.
      Parameters:
        `resourceUri` - the resource URI to resolve
        `description` - a description of the original resource that the URI was created for (for example, a class path location)
      Returns:
        a corresponding File object
      Throws:
        `FileNotFoundException` - if the URL cannot be resolved to a file in the file system

    - #### isFileURL

          public static boolean isFileURL(URL url)

      Determine whether the given URL points to a resource in the file system, that is, has protocol "file" or "vfs".
      Parameters:
        `url` - the URL to check
      Returns:
        whether the URL has been identified as a file system URL

    - #### isJarURL

          public static boolean isJarURL(URL url)

      Determine whether the given URL points to a resource in a jar file, that is, has protocol "jar", "zip", "wsjar" or "code-source".

      "zip" and "wsjar" are used by BEA WebLogic Server and IBM WebSphere, respectively, but can be treated like jar files. The same applies to "code-source" URLs on Oracle OC4J, provided that the path contains a jar separator.

      Parameters:
        `url` - the URL to check
      Returns:
        whether the URL has been identified as a JAR URL

    - #### extractJarFileURL

          public static URL extractJarFileURL(URL jarUrl)
                                       throws MalformedURLException

      Extract the URL for the actual jar file from the given URL (which may point to a resource in a jar file or to a jar file itself).
      Parameters:
        `jarUrl` - the original URL
      Returns:
        the URL for the actual jar file
      Throws:
        `MalformedURLException` - if no valid jar file URL could be extracted

    - #### toURI

          public static URI toURI(URL url)
                           throws URISyntaxException

      Create a URI instance for the given URL, replacing spaces with "%20" quotes first.

      Furthermore, this method works on JDK 1.4 as well, in contrast to the `URL.toURI()` method.

      Parameters:
        `url` - the URL to convert into a URI instance
      Returns:
        the URI instance
      Throws:
        `URISyntaxException` - if the URL wasn't a valid URI
      See Also:
        `URL.toURI()`

    - #### toURI

          public static URI toURI(String location)
                           throws URISyntaxException

      Create a URI instance for the given location String, replacing spaces with "%20" quotes first.
      Parameters:
        `location` - the location String to convert into a URI instance
      Returns:
        the URI instance
      Throws:
        `URISyntaxException` - if the location wasn't a valid URI

    - #### useCachesIfNecessary

          public static void useCachesIfNecessary(URLConnection con)

      Set the `"useCaches"` flag on the given connection, preferring `false` but leaving the flag at `true` for JNLP based resources.
      Parameters:
        `con` - the URLConnection to set the flag on