Class Resources


  • @Beta
    @GwtIncompatible
    public final class Resources
    extends Object
    Provides utility methods for working with resources in the classpath. Note that even though these methods use URL parameters, they are usually not appropriate for HTTP or other non-classpath resources.

    All method parameters must be non-null unless documented otherwise.

    Since:
    1.0
    Author:
    Chris Nokleberg, Ben Yu, Colin Decker
    • Method Detail

      • toByteArray

        public static byte[] toByteArray​(URL url)
                                  throws IOException
        Reads all bytes from a URL into a byte array.
        Parameters:
        url - the URL to read from
        Returns:
        a byte array containing all the bytes from the URL
        Throws:
        IOException - if an I/O error occurs
      • toString

        public static String toString​(URL url,
                                      Charset charset)
                               throws IOException
        Reads all characters from a URL into a String, using the given character set.
        Parameters:
        url - the URL to read from
        charset - the charset used to decode the input stream; see Charsets for helpful predefined constants
        Returns:
        a string containing all the characters from the URL
        Throws:
        IOException - if an I/O error occurs.
      • readLines

        @CanIgnoreReturnValue
        public static <T extends @Nullable Object> T readLines​(URL url,
                                                               Charset charset,
                                                               LineProcessor<T> callback)
                                                        throws IOException
        Streams lines from a URL, stopping when our callback returns false, or we have read all of the lines.
        Parameters:
        url - the URL to read from
        charset - the charset used to decode the input stream; see Charsets for helpful predefined constants
        callback - the LineProcessor to use to handle the lines
        Returns:
        the output of processing the lines
        Throws:
        IOException - if an I/O error occurs
      • readLines

        public static List<StringreadLines​(URL url,
                                             Charset charset)
                                      throws IOException
        Reads all of the lines from a URL. The lines do not include line-termination characters, but do include other leading and trailing whitespace.

        This method returns a mutable List. For an ImmutableList, use Resources.asCharSource(url, charset).readLines().

        Parameters:
        url - the URL to read from
        charset - the charset used to decode the input stream; see Charsets for helpful predefined constants
        Returns:
        a mutable List containing all the lines
        Throws:
        IOException - if an I/O error occurs
      • copy

        public static void copy​(URL from,
                                OutputStream to)
                         throws IOException
        Copies all bytes from a URL to an output stream.
        Parameters:
        from - the URL to read from
        to - the output stream
        Throws:
        IOException - if an I/O error occurs
      • getResource

        @CanIgnoreReturnValue
        public static URL getResource​(String resourceName)
        Returns a URL pointing to resourceName if the resource is found using the context class loader. In simple environments, the context class loader will find resources from the class path. In environments where different threads can have different class loaders, for example app servers, the context class loader will typically have been set to an appropriate loader for the current thread.

        In the unusual case where the context class loader is null, the class loader that loaded this class (Resources) will be used instead.

        Throws:
        IllegalArgumentException - if the resource is not found