背景
本文章是为了快速学习，更深入的了解一些内容而设定，一般地，复制代码即可运行。
Apache HttpClient
HttpClient是Apache Jakarta Common下子项目，用来提供高效的、最新的、功能丰富的支持HTTP协议的客户端编程工具包，并且支持HTTP协议最新的版本和建议。
Java Servlet实现服务器端
参考： Maven创建Web项目，Servlet、JSP，配置Tomcat运行
处理普通GET、POST请求的Servlet
package com.what21.servlet;
import com.fasterxml.jackson.databind.ObjectMapper;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.*;
@WebServlet("/service/general")
public class GeneralHttpServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
// 接收所有的header参数
Enumeration<String> headerEnumer = request.getHeaderNames();
System.out.println("-------------------------------------------------");
while (headerEnumer.hasMoreElements()) {
String name = headerEnumer.nextElement();
System.out.println(name + ":" + request.getHeader(name));
}
System.out.println("-------------------------------------------------");
Map<String, String[]> parameterMap = request.getParameterMap();
Set<String> keySet = parameterMap.keySet();
for (String key : keySet) {
System.out.println(key + ":" + Arrays.toString(parameterMap.get(key)));
}
System.out.println("-------------------------------------------------");
Map<String, Object> dataMap = new HashMap<>();
dataMap.put("code", "ok");
ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(dataMap);
response.setContentType("text/json;charset=UTF-8");
response.setCharacterEncoding("UTF-8");
PrintWriter writer = response.getWriter();
writer.print(json);
writer.flush();
}
}处理普通POST JSON请求的Servlet
package com.what21.servlet;
import com.fasterxml.jackson.databind.ObjectMapper;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.*;
@WebServlet("/service/json")
public class PostJsonHttpServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 接收所有的header参数
Enumeration<String> headerEnumer = request.getHeaderNames();
System.out.println("-------------------------------------------------");
while (headerEnumer.hasMoreElements()) {
String name = headerEnumer.nextElement();
System.out.println(name + ":" + request.getHeader(name));
}
System.out.println("-------------------------------------------------");
InputStream inputStream = request.getInputStream();
int len = -1;
byte buf[] = new byte[512];//缓冲区
ByteArrayOutputStream baos = new ByteArrayOutputStream();
while ((len = inputStream.read(buf)) != -1) {
baos.write(buf, 0, len);
}
String requestJson = new String(baos.toByteArray(), "UTF-8");
ObjectMapper objectMapper = new ObjectMapper();
Map<Object, Object> requestMap = objectMapper.readValue(requestJson, Map.class);
System.out.println("requestMap=" + requestMap);
System.out.println("-------------------------------------------------");
Map<String, Object> dataMap = new HashMap<>();
dataMap.put("code", "ok");
ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(dataMap);
response.setContentType("text/json;charset=UTF-8");
response.setCharacterEncoding("UTF-8");
PrintWriter writer = response.getWriter();
writer.print(json);
writer.flush();
}
}HttpClient4实现客户端调用
pom.xml
<dependencies> <!-- Web Dependencies --> <dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>3.1.0</version> <scope>provided</scope> </dependency> <!-- commons.lang3 --> <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-lang3</artifactId> <version>3.7</version> </dependency> <!-- 雪花算法 --> <dependency> <groupId>com.relops</groupId> <artifactId>snowflake</artifactId> <version>1.1</version> </dependency> <!-- jackson --> <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-core</artifactId> <version>2.13.1</version> </dependency> <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.13.1</version> </dependency> <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-annotations</artifactId> <version>2.13.1</version> </dependency> <!-- HttpClient--> <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient</artifactId> <version>4.5.13</version> </dependency> <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpmime</artifactId> <version>4.5.13</version> </dependency> <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpasyncclient</artifactId> <version>4.1</version> </dependency> <!--测试使用 --> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.11</version> <scope>test</scope> </dependency> <!-- lombok插件--> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.18.20</version> <scope>provided</scope> </dependency> </dependencies>
实现的工具类
package com.what21.httpclient4;
import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicHeader;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
import java.io.IOException;
import java.util.*;
public class HttpClientHelperUtils {
/**
* @param url
* @return
*/
public static String get(String url) {
String result = null;
HttpEntity httpEntity = null;
try {
CloseableHttpClient httpClient = HttpClients.createDefault();
// 创建POST
HttpGet httpGet = new HttpGet(url);
httpGet.setConfig(getRequestConfig());
// 设置头参数
Header header = new BasicHeader("Accept-Encoding", null);
httpGet.setHeader(header);
CloseableHttpResponse httpResponse = httpClient.execute(httpGet);
httpEntity = httpResponse.getEntity();
result = EntityUtils.toString(httpEntity);
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
EntityUtils.consume(httpEntity);
} catch (IOException e) {
// http请求释放资源异常
e.printStackTrace();
}
}
return result;
}
/**
* @param url
* @param paramsMap
* @return
*/
public static String post(String url, Map<String, String> paramsMap) {
String result = null;
HttpEntity httpEntity = null;
try {
CloseableHttpClient httpClient = HttpClients.createDefault();
// 创建POST
HttpPost httpPost = new HttpPost(url);
httpPost.setConfig(getRequestConfig());
// 设置头参数
Header header = new BasicHeader("Accept-Encoding", null);
httpPost.setHeader(header);
// 添加参数
List<NameValuePair> nameValuePairs = new ArrayList<>();
if (paramsMap != null && paramsMap.size() > 0) {
Set<String> keySet = paramsMap.keySet();
Iterator it = keySet.iterator();
while (it.hasNext()) {
String key = (String) it.next();
String value = paramsMap.get(key);
nameValuePairs.add(new BasicNameValuePair(key, value));
}
}
httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
// 执行
CloseableHttpResponse httpResponse = httpClient.execute(httpPost);
httpEntity = httpResponse.getEntity();
result = EntityUtils.toString(httpEntity);
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
EntityUtils.consume(httpEntity);
} catch (IOException e) {
// http请求释放资源异常
e.printStackTrace();
}
}
return result;
}
/**
* @param url
* @param json
* @return
*/
public static String postByContentTypeToJson(String url, String json) {
String result = null;
HttpEntity httpEntity = null;
try {
CloseableHttpClient httpClient = HttpClients.createDefault();
// 创建POST
HttpPost httpPost = new HttpPost(url);
httpPost.setConfig(getRequestConfig());
// 设置头参数
Header header = new BasicHeader("Accept-Encoding", null);
httpPost.setHeader(header);
// 头设置报文和通讯格式
StringEntity stringEntity = new StringEntity(json, ContentType.APPLICATION_JSON);
stringEntity.setContentEncoding("UTF-8");
httpPost.setEntity(stringEntity);
CloseableHttpResponse httpResponse = httpClient.execute(httpPost);
httpEntity = httpResponse.getEntity();
result = EntityUtils.toString(httpEntity);
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
EntityUtils.consume(httpEntity);
} catch (IOException e) {
// http请求释放资源异常
e.printStackTrace();
}
}
return result;
}
/**
* @return
*/
public static RequestConfig getRequestConfig() {
RequestConfig requestConfig = RequestConfig.custom()
.setSocketTimeout(180 * 1000) // 连接超时时间
.setConnectTimeout(180 * 1000) // 请求超时时间
.setConnectionRequestTimeout(180 * 1000) // 连接请求超时时间
.setRedirectsEnabled(true) // 重定向开关
.build();
return requestConfig;
}
}工具类的调用案例
package com.what21.httpclient4;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.util.HashMap;
import java.util.Map;
public class HttpClientHelperUtilsDemo {
public static void main(String[] args) {
// get调用
String getUrl = "http://localhost:9090/web/service/general?id=xfd&name=小奋斗";
String getResult = HttpClientHelperUtils.get(getUrl);
System.out.println(getResult);
//===================================================================//
// post context-type
String postUrl = "http://localhost:9090/web/service/general";
Map<String, String> paramsMap = new HashMap<>();
paramsMap.put("id", "xfd");
paramsMap.put("name", "小奋斗");
String postResult = HttpClientHelperUtils.post(postUrl, paramsMap);
System.out.println(postResult);
//===================================================================//
String postUrl2 = "http://localhost:9090/web/service/json";
String json = "{}";
try {
Map<String, String> jsonMap = new HashMap<>();
jsonMap.put("id", "xfd");
jsonMap.put("name", "小奋斗");
ObjectMapper mapper = new ObjectMapper();
json = mapper.writeValueAsString(jsonMap);
} catch (JsonProcessingException e) {
e.printStackTrace();
}
String postResultToJson = HttpClientHelperUtils.postByContentTypeToJson(postUrl2, json);
System.out.println(postResultToJson);
}
}
