Guava（Resources用法） 读取 classpath 中的文件、读取HTTP

假设 classpath 中有个文件是： hello.txt

guava 读取其中的文件内容：

URL url = Resources.getResource(“hello.txt");
List<String> lines = Resources.asCharSource(url, Charsets.UTF_8).readLines();

 读取 http://www.iteye.com/ 的内容：

URL url = new URL("http://www.iteye.com/");
List<String> lines = Resources.asCharSource(url, Charsets.UTF_8).readLines();

下面是 Guava 中Resources的官网 API。

==============

com.google.common.io

Class Resources

• java.lang.Object
• • com.google.common.io.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 Summary

    All MethodsStatic MethodsConcrete Methods Modifier and Type Method and Description

    static ByteSource	asByteSource(URL url) Returns a  ByteSource that reads from the given URL.
    static CharSource	asCharSource(URL url, Charset charset) Returns a  CharSource that reads from the given URL using the given character set.
    static void	copy(URL from, OutputStream to) Copies all bytes from a URL to an output stream.
    static URL	getResource(Class<?> contextClass, String resourceName) Given a  resourceName that is relative to  contextClass, returns a  URL pointing to the named resource.
    static URL	getResource(String resourceName) Returns a  URL pointing to  resourceName if the resource is found using the  context class loader.
    static List<String>	readLines(URL url, Charset charset) Reads all of the lines from a URL.
    static <T> T	readLines(URL url, Charset charset, LineProcessor<T> callback) Streams lines from a URL, stopping when our callback returns false, or we have read all of the lines.
    static byte[]	toByteArray(URL url) Reads all bytes from a URL into a byte array.
    static String	toString(URL url, Charset charset) Reads all characters from a URL into a  String, using the given character set.

    • Methods inherited from class java.lang.Object

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

• • Method Detail

    • asByteSource

      public static ByteSource asByteSource(URL url)

      Returns a  ByteSource that reads from the given URL.
      Since:
      14.0

    • asCharSource

      public static CharSource asCharSource(URL url,
                                            Charset charset)

      Returns a  CharSource that reads from the given URL using the given character set.
      Since:
      14.0

    • 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

      public static <T> 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<String> readLines(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

      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

    • getResource

      public static URL getResource(Class<?> contextClass,
                                    String resourceName)

      Given a  resourceName that is relative to  contextClass, returns a  URL pointing to the named resource.
      Throws:
      IllegalArgumentException - if the resource is not found