使用HttpClient发送post请求时会遇到服务端收不到参数的情况，查找了一下原因是因为大部分使用Httpclient模拟post请求时都会把参数放在Entity里面，示例如下：
// 创建Http Post请求
HttpPost httpPost = new HttpPost(url);
// 创建参数列表
if (param != null) {
List<NameValuePair> paramList = new ArrayList<>();
for (String key : param.keySet()) {
paramList.add(new BasicNameValuePair(key, param.get(key)));
}
// 模拟表单
UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList);
httpPost.setEntity(entity);
}
// 执行http请求
response = httpClient.execute(httpPost);
resultString = EntityUtils.toString(response.getEntity(),"utf-8");
上面的这种设置参数的方式通过request.getParameter("key")的方式获取不到参数，所以如果想通过request.getParameter("key")获取参数，则需要修改HttpClient模拟post请求时设置参数的方式，示例如下：
private static HttpPost postForm(String url, Map<String, String> params) {
URIBuilder builder;
HttpPost httpost = null;
try {
builder = new URIBuilder(url);
List<NameValuePair> nvps = new ArrayList <NameValuePair>();
Set<String> keySet = params.keySet();
for(String key : keySet) {
nvps.add(new BasicNameValuePair(key, params.get(key)));
}
builder.setCharset(Consts.UTF_8);
builder.setParameters(nvps);
httpost = new HttpPost(builder.build());
} catch (URISyntaxException e) {
e.printStackTrace();
}
return httpost;
}
使用URIBuilder将参数加到parameters里面，这样就可以通过request.getParameter("key")的方式获取到参数，或者是Spring框架里面直接使用实体类来接收参数。
最后附上完整的HttpUtils类
package com.jeeplus.modules.tools.utils;
import java.io.IOException;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.apache.http.Consts;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.entity.ContentType;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
import org.apache.log4j.Logger;
/**
* ClassName: HttpPostTest <br/>
* Function: update CloseableHttpClient <br/>
* date: Mar 20, 2019 11:09:00 AM <br/>
*
* @author idaidai
* @version 2.0
* @since JDK 1.8
*/
public class HttpPostTest {
private static Logger log = Logger.getLogger(HttpPostTest.class);
Map<String, String> params;
String url;
static String code;
public static String post(String url, Map<String, String> params) {
CloseableHttpClient httpclient = HttpClientBuilder.create().build();
String body = null;
log.info("create httppost:" + url);
HttpPost post = postForm(url, params);
body = invoke(httpclient, post);
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
return body;
}
public HttpPostTest(String url, Map<String, String> params){
this.url = url;
this.params = params;
}
public static String get(String url) {
CloseableHttpClient httpclient = HttpClientBuilder.create().build();
String body = null;
log.info("create httppost:" + url);
HttpGet get = new HttpGet(url);
body = invoke(httpclient, get);
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
return body;
}
private static String invoke(CloseableHttpClient httpclient,
HttpUriRequest httpost) {
HttpResponse response = sendRequest(httpclient, httpost);
String body = paseResponse(response);
return body;
}
private static String paseResponse(HttpResponse response) {
log.info("get response from http server..");
HttpEntity entity = response.getEntity();
log.info("response status: " + response.getStatusLine());
String charset = ContentType.get(entity).getCharset().name();
log.info(charset);
String body = null;
try {
body = EntityUtils.toString(entity);
log.info(body);
} catch (ParseException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
code = "response status: " + response.getStatusLine() +"\n";
return body;
}
private static HttpResponse sendRequest(CloseableHttpClient httpclient,
HttpUriRequest httpost) {
log.info("execute post...");
HttpResponse response = null;
try {
response = httpclient.execute(httpost);
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return response;
}
private static HttpPost postForm(String url, Map<String, String> params) {
URIBuilder builder;
HttpPost httpost = null;
try {
builder = new URIBuilder(url);
List<NameValuePair> nvps = new ArrayList <NameValuePair>();
Set<String> keySet = params.keySet();
for(String key : keySet) {
nvps.add(new BasicNameValuePair(key, params.get(key)));
}
builder.setCharset(Consts.UTF_8);
builder.setParameters(nvps);
httpost = new HttpPost(builder.build());
} catch (URISyntaxException e) {
e.printStackTrace();
}
return httpost;
}
public String postWithCode(){
String xml = HttpPostTest.post(url, params);
return code + xml;
}
}