EntityUtils 工具类

EntityUtils对象是org.apache.http.util下的一个工具类，用官方的解释是为HttpEntity对象提供的静态帮助类

package org.apache.http.util;import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.nio.charset.UnsupportedCharsetException;import org.apache.http.HeaderElement;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
import org.apache.http.entity.ContentType;
import org.apache.http.protocol.HTTP;/*** Static helpers for dealing with {@link HttpEntity}s.** @since 4.0*/
public final class EntityUtils {private EntityUtils() {}/*** Ensures that the entity content is fully consumed and the content stream, if exists,* is closed. The process is done, <i>quietly</i> , without throwing any IOException.** @param entity the entity to consume.*** @since 4.2*/public static void consumeQuietly(final HttpEntity entity) {try {consume(entity);} catch (final IOException ignore) {}}/*** Ensures that the entity content is fully consumed and the content stream, if exists,* is closed.** @param entity the entity to consume.* @throws IOException if an error occurs reading the input stream** @since 4.1*/public static void consume(final HttpEntity entity) throws IOException {if (entity == null) {return;}if (entity.isStreaming()) {final InputStream instream = entity.getContent();if (instream != null) {instream.close();}}}/*** Updates an entity in a response by first consuming an existing entity, then setting the new one.** @param response the response with an entity to update; must not be null.* @param entity the entity to set in the response.* @throws IOException if an error occurs while reading the input stream on the existing* entity.* @throws IllegalArgumentException if response is null.** @since 4.3*/public static void updateEntity(final HttpResponse response, final HttpEntity entity) throws IOException {Args.notNull(response, "Response");consume(response.getEntity());response.setEntity(entity);}/*** Read the contents of an entity and return it as a byte array.** @param entity the entity to read from=* @return byte array containing the entity content. May be null if*   {@link HttpEntity#getContent()} is null.* @throws IOException if an error occurs reading the input stream* @throws IllegalArgumentException if entity is null or if content length &gt; Integer.MAX_VALUE*/public static byte[] toByteArray(final HttpEntity entity) throws IOException {Args.notNull(entity, "Entity");final InputStream instream = entity.getContent();if (instream == null) {return null;}try {Args.check(entity.getContentLength() <= Integer.MAX_VALUE,"HTTP entity too large to be buffered in memory");int i = (int)entity.getContentLength();if (i < 0) {i = 4096;}final ByteArrayBuffer buffer = new ByteArrayBuffer(i);final byte[] tmp = new byte[4096];int l;while((l = instream.read(tmp)) != -1) {buffer.append(tmp, 0, l);}return buffer.toByteArray();} finally {instream.close();}}/*** Obtains character set of the entity, if known.** @param entity must not be null* @return the character set, or null if not found* @throws ParseException if header elements cannot be parsed* @throws IllegalArgumentException if entity is null** @deprecated (4.1.3) use {@link ContentType#getOrDefault(HttpEntity)}*/@Deprecatedpublic static String getContentCharSet(final HttpEntity entity) throws ParseException {Args.notNull(entity, "Entity");String charset = null;if (entity.getContentType() != null) {final HeaderElement values[] = entity.getContentType().getElements();if (values.length > 0) {final NameValuePair param = values[0].getParameterByName("charset");if (param != null) {charset = param.getValue();}}}return charset;}/*** Obtains MIME type of the entity, if known.** @param entity must not be null* @return the character set, or null if not found* @throws ParseException if header elements cannot be parsed* @throws IllegalArgumentException if entity is null** @since 4.1** @deprecated (4.1.3) use {@link ContentType#getOrDefault(HttpEntity)}*/@Deprecatedpublic static String getContentMimeType(final HttpEntity entity) throws ParseException {Args.notNull(entity, "Entity");String mimeType = null;if (entity.getContentType() != null) {final HeaderElement values[] = entity.getContentType().getElements();if (values.length > 0) {mimeType = values[0].getName();}}return mimeType;}private static String toString(final HttpEntity entity,final ContentType contentType) throws IOException {final InputStream instream = entity.getContent();if (instream == null) {return null;}try {Args.check(entity.getContentLength() <= Integer.MAX_VALUE,"HTTP entity too large to be buffered in memory");int i = (int)entity.getContentLength();if (i < 0) {i = 4096;}Charset charset = null;if (contentType != null) {charset = contentType.getCharset();if (charset == null) {final ContentType defaultContentType = ContentType.getByMimeType(contentType.getMimeType());charset = defaultContentType != null ? defaultContentType.getCharset() : null;}}if (charset == null) {charset = HTTP.DEF_CONTENT_CHARSET;}final Reader reader = new InputStreamReader(instream, charset);final CharArrayBuffer buffer = new CharArrayBuffer(i);final char[] tmp = new char[1024];int l;while((l = reader.read(tmp)) != -1) {buffer.append(tmp, 0, l);}return buffer.toString();} finally {instream.close();}}/*** Get the entity content as a String, using the provided default character set* if none is found in the entity.* If defaultCharset is null, the default "ISO-8859-1" is used.** @param entity must not be null* @param defaultCharset character set to be applied if none found in the entity,* or if the entity provided charset is invalid or not available.* @return the entity content as a String. May be null if*   {@link HttpEntity#getContent()} is null.* @throws ParseException if header elements cannot be parsed* @throws IllegalArgumentException if entity is null or if content length &gt; Integer.MAX_VALUE* @throws IOException if an error occurs reading the input stream* @throws java.nio.charset.UnsupportedCharsetException Thrown when the named entity's charset is not available in* this instance of the Java virtual machine and no defaultCharset is provided.*/public static String toString(final HttpEntity entity, final Charset defaultCharset) throws IOException, ParseException {Args.notNull(entity, "Entity");ContentType contentType = null;try {contentType = ContentType.get(entity);} catch (final UnsupportedCharsetException ex) {if (defaultCharset == null) {throw new UnsupportedEncodingException(ex.getMessage());}}if (contentType != null) {if (contentType.getCharset() == null) {contentType = contentType.withCharset(defaultCharset);}} else {contentType = ContentType.DEFAULT_TEXT.withCharset(defaultCharset);}return toString(entity, contentType);}/*** Get the entity content as a String, using the provided default character set* if none is found in the entity.* If defaultCharset is null, the default "ISO-8859-1" is used.** @param entity must not be null* @param defaultCharset character set to be applied if none found in the entity* @return the entity content as a String. May be null if*   {@link HttpEntity#getContent()} is null.* @throws ParseException if header elements cannot be parsed* @throws IllegalArgumentException if entity is null or if content length &gt; Integer.MAX_VALUE* @throws IOException if an error occurs reading the input stream* @throws java.nio.charset.UnsupportedCharsetException Thrown when the named charset is not available in* this instance of the Java virtual machine*/public static String toString(final HttpEntity entity, final String defaultCharset) throws IOException, ParseException {return toString(entity, defaultCharset != null ? Charset.forName(defaultCharset) : null);}/*** Read the contents of an entity and return it as a String.* The content is converted using the character set from the entity (if any),* failing that, "ISO-8859-1" is used.** @param entity the entity to convert to a string; must not be null* @return String containing the content.* @throws ParseException if header elements cannot be parsed* @throws IllegalArgumentException if entity is null or if content length &gt; Integer.MAX_VALUE* @throws IOException if an error occurs reading the input stream* @throws java.nio.charset.UnsupportedCharsetException Thrown when the named charset is not available in* this instance of the Java virtual machine*/public static String toString(final HttpEntity entity) throws IOException, ParseException {Args.notNull(entity, "Entity");return toString(entity, ContentType.get(entity));}}

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