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 * to you under the Apache License, Version 2.0 (the
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 * KIND, either express or implied.  See the License for the
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package org.apache.http.protocol;

import java.io.IOException;

import org.apache.http.HttpEntity;
import org.apache.http.HttpException;
import org.apache.http.HttpResponse;
import org.apache.http.HttpResponseInterceptor;
import org.apache.http.HttpStatus;
import org.apache.http.HttpVersion;
import org.apache.http.ProtocolException;
import org.apache.http.ProtocolVersion;
import org.apache.http.annotation.ThreadingBehavior;
import org.apache.http.annotation.Contract;
import org.apache.http.util.Args;

ResponseContent is the most important interceptor for outgoing responses. It is responsible for delimiting content length by adding Content-Length or Transfer-Content headers based on the properties of the enclosed entity and the protocol version. This interceptor is required for correct functioning of server side protocol processors. 
Since:
4.0/**
 * ResponseContent is the most important interceptor for outgoing responses.
 * It is responsible for delimiting content length by adding
 * {@code Content-Length} or {@code Transfer-Content} headers based
 * on the properties of the enclosed entity and the protocol version.
 * This interceptor is required for correct functioning of server side protocol
 * processors.
 *
 * @since 4.0
 */
@Contract(threading = ThreadingBehavior.IMMUTABLE)
public class ResponseContent implements HttpResponseInterceptor {

    private final boolean overwrite;

    
Default constructor. The Content-Length or Transfer-Encoding will cause the interceptor to throw ProtocolException if already present in the response message. /**
     * Default constructor. The {@code Content-Length} or {@code Transfer-Encoding}
     * will cause the interceptor to throw {@link ProtocolException} if already present in the
     * response message.
     */
    public ResponseContent() {
        this(false);
    }

    
Constructor that can be used to fine-tune behavior of this interceptor.
Params:
overwrite – If set to true the Content-Length and Transfer-Encoding headers will be created or updated if already present. If set to false the Content-Length and Transfer-Encoding headers will cause the interceptor to throw ProtocolException if already present in the response message.
Since:
4.2/**
     * Constructor that can be used to fine-tune behavior of this interceptor.
     *
     * @param overwrite If set to {@code true} the {@code Content-Length} and
     * {@code Transfer-Encoding} headers will be created or updated if already present.
     * If set to {@code false} the {@code Content-Length} and
     * {@code Transfer-Encoding} headers will cause the interceptor to throw
     * {@link ProtocolException} if already present in the response message.
     *
     * @since 4.2
     */
     public ResponseContent(final boolean overwrite) {
         super();
         this.overwrite = overwrite;
    }

    
Processes the response (possibly updating or inserting) Content-Length and Transfer-Encoding headers.
Params:
response – The HttpResponse to modify.
context – Unused.
Throws:
ProtocolException – If either the Content-Length or Transfer-Encoding headers are found.
IllegalArgumentException – If the response is null./**
     * Processes the response (possibly updating or inserting) Content-Length and Transfer-Encoding headers.
     * @param response The HttpResponse to modify.
     * @param context Unused.
     * @throws ProtocolException If either the Content-Length or Transfer-Encoding headers are found.
     * @throws IllegalArgumentException If the response is null.
     */
    @Override
    public void process(final HttpResponse response, final HttpContext context)
            throws HttpException, IOException {
        Args.notNull(response, "HTTP response");
        if (this.overwrite) {
            response.removeHeaders(HTTP.TRANSFER_ENCODING);
            response.removeHeaders(HTTP.CONTENT_LEN);
        } else {
            if (response.containsHeader(HTTP.TRANSFER_ENCODING)) {
                throw new ProtocolException("Transfer-encoding header already present");
            }
            if (response.containsHeader(HTTP.CONTENT_LEN)) {
                throw new ProtocolException("Content-Length header already present");
            }
        }
        final ProtocolVersion ver = response.getStatusLine().getProtocolVersion();
        final HttpEntity entity = response.getEntity();
        if (entity != null) {
            final long len = entity.getContentLength();
            if (entity.isChunked() && !ver.lessEquals(HttpVersion.HTTP_1_0)) {
                response.addHeader(HTTP.TRANSFER_ENCODING, HTTP.CHUNK_CODING);
            } else if (len >= 0) {
                response.addHeader(HTTP.CONTENT_LEN, Long.toString(entity.getContentLength()));
            }
            // Specify a content type if known
            if (entity.getContentType() != null && !response.containsHeader(
                    HTTP.CONTENT_TYPE )) {
                response.addHeader(entity.getContentType());
            }
            // Specify a content encoding if known
            if (entity.getContentEncoding() != null && !response.containsHeader(
                    HTTP.CONTENT_ENCODING)) {
                response.addHeader(entity.getContentEncoding());
            }
        } else {
            final int status = response.getStatusLine().getStatusCode();
            if (status != HttpStatus.SC_NO_CONTENT
                    && status != HttpStatus.SC_NOT_MODIFIED
                    && status != HttpStatus.SC_RESET_CONTENT) {
                response.addHeader(HTTP.CONTENT_LEN, "0");
            }
        }
    }

}