关于HttpClient 4从4.2版本Deprecated UTF-8等编码常量的说明

HttpClient4在HTTP类里原先定义了一系列编码集常量UTF-8,UTF-16等，但从4.2版本开始，这些常量被标识了deprecated标志。

 /**
     * @deprecated (4.2)
     */
    @Deprecated
    public static final String UTF_8 = "UTF-8";
    /**
     * @deprecated (4.2)
     */
    @Deprecated
    public static final String UTF_16 = "UTF-16";
    /**
     * @deprecated (4.2)
     */
    @Deprecated
    public static final String US_ASCII = "US-ASCII";
    /**
     * @deprecated (4.2)
     */
    @Deprecated
    public static final String ASCII = "ASCII";

    这是由于从JDK7起，引入了StandardCharsets类，标识了这些编码集常量

   

/**
 * Constant definitions for the standard {@link Charset Charsets}. These
 * charsets are guaranteed to be available on every implementation of the Java
 * platform.
 *
 * @see <a href="Charset#standard">Standard Charsets</a>
 * @since 1.7
 */
public final class StandardCharsets {

    private StandardCharsets() {
        throw new AssertionError("No java.nio.charset.StandardCharsets instances for you!");
    }
    /**
     * Seven-bit ASCII, a.k.a. ISO646-US, a.k.a. the Basic Latin block of the
     * Unicode character set
     */
    public static final Charset US_ASCII = Charset.forName("US-ASCII");
    /**
     * ISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1
     */
    public static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
    /**
     * Eight-bit UCS Transformation Format
     */
    public static final Charset UTF_8 = Charset.forName("UTF-8");
    /**
     * Sixteen-bit UCS Transformation Format, big-endian byte order
     */
    public static final Charset UTF_16BE = Charset.forName("UTF-16BE");
    /**
     * Sixteen-bit UCS Transformation Format, little-endian byte order
     */
    public static final Charset UTF_16LE = Charset.forName("UTF-16LE");
    /**
     * Sixteen-bit UCS Transformation Format, byte order identified by an
     * optional byte-order mark
     */
    public static final Charset UTF_16 = Charset.forName("UTF-16");
}

所以之后咱们使用HttpClient 4发送POST请求，设定编码集时，不须要再使用HTTP类中的编码集常量，直接使用StandardCharsets类中的编码集常量便可