HttpClient4.6的使用

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1）简介：

　　HttpClient是apache的开源项目，弥补了Java自带的URLConnection功能不足，操作繁琐的缺点。

2）简单使用：

　　a）get方式请求

     /**
      * 发送get请求，get表单提交
      * 获取数返回的json数据
      */
     @Test
     public void httpGet() {

         //创建httpClient对象
         HttpClient httpClient = HttpClients.createDefault();//4.3之后的都采用该方法生成httpClient对象
         //创建url
         String url = "http://localhost:8080/day29_struts/dataconvert?user.name=yyq&user.age=20&user.birthday=2012-8-9";
         //创建httpGet对象
         HttpGet httpget = new HttpGet(url);
         System.out.println("URI：" + httpget.getURI());
         System.out.println("requestLine：" + httpget.getRequestLine());

         try {

             //执行get请求
             HttpResponse response = httpClient.execute(httpget);

             //打印响应状态
             System.out.println("响应状态：" + response.getStatusLine());

             //获取响应体
             HttpEntity entity = response.getEntity();
             if (entity != null) {
                 //打印响应内容长度
                 System.out.println("内容长度：" + entity.getContentLength());
                 //打印响应类型
                 System.out.println("返回类型：" + entity.getContentType());
                 //响应体内容
                 System.out.println("实体内容：" + EntityUtils.toString(entity));

             }

         } catch (ClientProtocolException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }

     }

结果：

URI：http://localhost:8080/day29_struts/dataconvert?user.name=yyq&user.age=20&user.birthday=2012-8-9
requestLine：GET http://localhost:8080/day29_struts/dataconvert?user.name=yyq&user.age=20&user.birthday=2012-8-9 HTTP/1.1
响应状态：HTTP/1.1 200 OK
内容长度：78
返回类型：Content-Type: text/html;charset=UTF-8
实体内容：{"user.name":yyq, "user.age":20, "user.birthday":Thu Aug 09 00:00:00 CST 2012}

　　

　　b）post方式提交（表单提交推荐使用，编码好处理，而且请求数据没有限制）

 /**
      * 推荐方式
      * 发送post请求，即表单post提交
      */
     @Test
     public void httpPost() {
         //创建HttpClient实例
         HttpClient httpClient = HttpClients.createDefault();
         //URL
         String url = "http://localhost:8080/test/TestServlet";
         //获取HttpPost实例
         HttpPost httpPost = new HttpPost(url);
         System.out.println(httpPost.getRequestLine());

         try {
             //设置post请求参数
             List<NameValuePair> params = new ArrayList<NameValuePair>();
             params.add(new BasicNameValuePair("id", "10"));
             params.add(new BasicNameValuePair("name", "yyq"));
             //把参数装进post请求体
             httpPost.setEntity(new UrlEncodedFormEntity(params, "utf-8"));

             //获取response实例
             HttpResponse response = httpClient.execute(httpPost);

             //响应状态
             System.out.println(response.getStatusLine());

             //获取响应体
             HttpEntity entity = response.getEntity();

             if (entity != null) {

                 System.out.println(EntityUtils.toString(entity, "utf-8"));

             }

         } catch (ClientProtocolException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }

     }

　　结果：

　　POST http://localhost:8080/test/TestServlet HTTP/1.1
　　HTTP/1.1 200 OK

　　

　　c）文件上传与下载

　　　　服务器端（采用tomcat）

 package servlet;

 import java.io.File;
 import java.io.IOException;
 import java.util.List;

 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import org.apache.commons.fileupload.FileItem;
 import org.apache.commons.fileupload.FileUploadException;
 import org.apache.commons.fileupload.disk.DiskFileItemFactory;
 import org.apache.commons.fileupload.servlet.ServletFileUpload;

 public class UploadServlet extends HttpServlet {

     public void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {

         request.setCharacterEncoding("utf-8");
         response.setContentType("text/html;charset=utf-8");

         //检测是不是存在上传文件，如果不存在则按一般方式解决
         boolean isMultipart = ServletFileUpload.isMultipartContent(request);
         if (isMultipart) {

             try {
                 DiskFileItemFactory factory = new DiskFileItemFactory();
                 //指定在内存中缓存数据大小,单位为byte,这里设为1Mb
                 factory.setSizeThreshold(1024*1024);
                 //设置一旦文件大小超过getSizeThreshold()的值时数据存放在硬盘的目录 ，老提示找不到路径，气得要死，无奈注释掉用tomcat自带的temp目录
                 //factory.setRepository(new File(getServletContext().getRealPath("uploadFile/tem")));  

                 //实例化文件上传对象
                 ServletFileUpload upload = new ServletFileUpload(factory);
                 //设置单个文件最大限制
                 upload.setFileSizeMax(500*1024*1024);
                 //设置总文件限制
                 upload.setSizeMax(200*1024*1024);
                 //设置编码
                 upload.setHeaderEncoding("utf-8");
                 //设置监视器，显示上传进度

                 //解析请求
                 List<FileItem> items = upload.parseRequest(request);
                 //解析表单
                 if (items != null) {
                     System.out.println(items.size());

                     for (FileItem fileItem : items) {

                         //如果是普通表单格式
                         if (fileItem.isFormField()) {

                             response.getWriter().print("---普通文本内容---");
                             System.out.println("文本类型：" + fileItem.getContentType());
                             System.out.println("表单属性名：" + fileItem.getFieldName());
                             System.out.println("表单值：" + fileItem.getString("utf-8"));

                         } else {

                             System.out.println("表单属性名：" + fileItem.getFieldName());
                             //上传的文件名
                             String fileName = fileItem.getName();
                             //把文件写在当前应用的upload目录
                             String basePath = getServletContext().getRealPath("/upload");
                             fileItem.write(new File(basePath, fileName));
                             //删除缓存区
                             fileItem.delete();

                         }

                     }

                 }

             } catch (FileUploadException e) {
                 e.printStackTrace();
             } catch (Exception e) {
                 e.printStackTrace();
             }

         } else {

         }

     }

     @Override
     protected void doPost(HttpServletRequest req, HttpServletResponse resp)
             throws ServletException, IOException {
         doGet(req, resp);
     }

 }

　　　　客户端：

     /**
      * 上传文件，post方式
      * 包含普通内容和上传的文件
      */
     @Test
     public void fileUpload() {

         HttpClient httpClient = HttpClients.createDefault();

          String url = "http://localhost:8080/test/UploadServlet";
          HttpPost httpPost = new HttpPost(url);

          /**
           *  封装到HttpEneity中
           * 使用MultipartEntityBuilder.create().build()生成该对象
           * 原来的new MultipartEntity()已废弃
           *
           * 封装请求体的两种方式：
           * 1，可以创建StringBody和FileBody封装文本和文件
           * 2，直接使用MultipartEntityBuilder.create()
           * 的addBinaryBody(name, File)封装文件
           * addTextBody(name, text, ContentType)封装文本
           */
          //普通数据的封装
          StringBody sb = new StringBody("yyq",
                  ContentType.create("text/plain", "utf-8"));

          //文件封装
          FileBody fb = new FileBody(new File("E:/App/CodeBlocks.zip"));
          HttpEntity reqEntity = MultipartEntityBuilder.create()
 //             .addPart("name", sb)
             .addTextBody("name", "yyq2",  ContentType.create("text/plain", "utf-8"))
 //             .addPart("file", fb)
              .addBinaryBody("name", new File("E:/App/CodeBlocks.zip"))
              .build();

          //4，请求体封装到post中
          httpPost.setEntity(reqEntity);

          try {
             HttpResponse response = httpClient.execute(httpPost);

             HttpEntity entity = response.getEntity();

             if (response.getStatusLine().getStatusCode() == 200) {
                 System.out.println(EntityUtils.toString(entity, "utf-8"));
             }

         } catch (ClientProtocolException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }

     }

附：HTTPUtils，同步方式，异步还是okhttp吧

 public class HttpClientUtil {

     public static String doGet(String url, Map<String, String> param) {

         // 创建Httpclient对象
         CloseableHttpClient httpclient = HttpClients.createDefault();

         String resultString = "";
         CloseableHttpResponse response = null;
         try {
             // 创建uri
             URIBuilder builder = new URIBuilder(url);
             if (param != null) {
                 for (String key : param.keySet()) {
                     builder.addParameter(key, param.get(key));
                 }
             }
             URI uri = builder.build();

             // 创建http GET请求
             HttpGet httpGet = new HttpGet(uri);

             // 执行请求
             response = httpclient.execute(httpGet);
             // 判断返回状态是否为200
             if (response.getStatusLine().getStatusCode() == 200) {
                 resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
             }
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
             try {
                 if (response != null) {
                     response.close();
                 }
                 httpclient.close();
             } catch (IOException e) {
                 e.printStackTrace();
             }
         }
         return resultString;
     }

     public static String doGet(String url) {
         return doGet(url, null);
     }

     public static String doPost(String url, Map<String, String> param) {
         // 创建Httpclient对象
         CloseableHttpClient httpClient = HttpClients.createDefault();
         CloseableHttpResponse response = null;
         String resultString = "";
         try {
             // 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");
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
             try {
                 response.close();
             } catch (IOException e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
             }
         }

         return resultString;
     }

     public static String doPost(String url) {
         return doPost(url, null);
     }

     public static String doPostJson(String url, String json) {
         // 创建Httpclient对象
         CloseableHttpClient httpClient = HttpClients.createDefault();
         CloseableHttpResponse response = null;
         String resultString = "";
         try {
             // 创建Http Post请求
             HttpPost httpPost = new HttpPost(url);
             // 创建请求内容
             StringEntity entity = new StringEntity(json, ContentType.APPLICATION_JSON);
             httpPost.setEntity(entity);
             // 执行http请求
             response = httpClient.execute(httpPost);
             resultString = EntityUtils.toString(response.getEntity(), "utf-8");
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
             try {
                 response.close();
             } catch (IOException e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
             }
         }

         return resultString;
     }
 }