HttpClient: Content-Length header already present解决及分析-蒲公英云

HttpClient: Content-Length header already present解决及分析

快来打我* 2023-06-16 02:22 62阅读 0赞

在用HttpClient的时候出现如下问题：

org.apache.http.client.ClientProtocolException
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:822)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:754)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:732)
……
Caused by: org.apache.http.ProtocolException: Content-Length header already present
at org.apache.http.protocol.RequestContent.process(RequestContent.java:67)
at org.apache.http.protocol.ImmutableHttpProcessor.process(ImmutableHttpProcessor.java:108)
at org.apache.http.protocol.HttpRequestExecutor.preProcess(HttpRequestExecutor.java:174)
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:462)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:820)
... 27 more

出现上面的问题是发送请求的时候设置了请求头Content-Length参数。
解决办法：把设置的请求头Content-Length参数去掉。

分析原因：
跟踪代码:查看HttpClient中RequestContent类的process方法，看到当body非空时，会自动加上Content-Length请求头及其对应值，不需要自己手动加上它。加上就会抛出上面的异常。
源码：

public class RequestContent implements HttpRequestInterceptor {

private final boolean overwrite;
public RequestContent() { 
    this(false);
}
public RequestContent(boolean overwrite) { 
    this.overwrite = overwrite;
}
public void process(HttpRequest request, HttpContext context) throws HttpException, IOException { 
    Args.notNull(request, "HTTP request");
    if (request instanceof HttpEntityEnclosingRequest) { 
        if (this.overwrite) { 
            request.removeHeaders("Transfer-Encoding");
            request.removeHeaders("Content-Length");
        } else { 
            if (request.containsHeader("Transfer-Encoding")) { 
                throw new ProtocolException("Transfer-encoding header already present");
            }
            if (request.containsHeader("Content-Length")) { 
                throw new ProtocolException("Content-Length header already present");
            }
        }
        ProtocolVersion ver = request.getRequestLine().getProtocolVersion();
        HttpEntity entity = ((HttpEntityEnclosingRequest)request).getEntity();
        if (entity == null) { 
            request.addHeader("Content-Length", "0");
            return;
        }
        if (!entity.isChunked() && entity.getContentLength() >= 0L) { 
            //计算请求头的长度
            request.addHeader("Content-Length", Long.toString(entity.getContentLength()));
        } else { 
            if (ver.lessEquals(HttpVersion.HTTP_1_0)) { 
                throw new ProtocolException("Chunked transfer encoding not allowed for " + ver);
            }
            request.addHeader("Transfer-Encoding", "chunked");
        }
        if (entity.getContentType() != null && !request.containsHeader("Content-Type")) { 
            request.addHeader(entity.getContentType());
        }
        if (entity.getContentEncoding() != null && !request.containsHeader("Content-Encoding")) { 
            request.addHeader(entity.getContentEncoding());
        }
    }
}