java网络编程

• 页面请求文本数据

public String getContent(String url) {
    OkHttpClient okHttpClient=new OkHttpClient();
    Request request=new Request.Builder().url(url).build();
    Call call=okHttpClient.newCall(request);
    String result=null;
    try {
      result=call.execute().body().string();
    } catch (IOException e) {
      System.out.println("request "+url+" error");
      e.printStackTrace();
    }
    return result;
}
 public static void main(String[] args) {
    GetPage getPage = new GetPage();
    String url ="" ;
    String content =getPage.getContent(url) ;

    System.out.println("API调用结果");
    System.out.println(content);

  }

• 页面请求二进制数据

  public byte[] getContent(String url) {
      OkHttpClient okHttpClient=new OkHttpClient();
      Request request=new Request.Builder().url(url).build();
      Call call=okHttpClient.newCall(request);
      byte[] result=null;
      try {
        result=call.execute().body().byte();
      } catch (IOException e) {
        System.out.println("request "+url+" error");
        e.printStackTrace();
      }
      return result;
  }
  
  

依赖：

<!-- https://mvnrepository.com/artifact/com.squareup.okhttp3/okhttp -->
<dependency>
 <groupId>com.squareup.okhttp3</groupId>
 <artifactId>okhttp</artifactId>
 <version>4.1.0</version>
</dependency>

• okhttp3中的post操作

  1. post表单数据

  public String postContent(String url, Map<String, String> formData) {
      // okHttpClient 实例
      OkHttpClient okHttpClient = new OkHttpClient();
      //post方式提交的数据
    	Builder builder = new FormBody.Builder();
      // 放入表单数据
      for(String key: formData.keySet())
      {
        builder.add(key,formData.get(key));
      }
      // 构建 FormBody 对象
      FormBody formBody = builder.build();
      // 指定 post 方式提交FormBody
      Request request = new Request.Builder().url(url).post(formBody).build();
      // 使用client去请求
      Call call = okHttpClient.newCall(request);
      // 返回结果字符串
      String result = null;
      try {
        // 获得返回结果
        result = call.execute().body().string();
      } catch (IOException e) {
        // 抓取异常
        System.out.println("request " + url + " error . ");
        e.printStackTrace();
      }
      return result;
    }
  
    public static void main(String[] args) {
      String url = "";
      Map<String, String> formData = new HashMap();
      formData.put("","" );
  
      FormPoster poster = new FormPoster();
      String content = poster.postContent(url, formData);
  
      System.out.println("API调用结果");
      System.out.println(content);
    }
  

  2. postJSON数据

private static final MediaType JSON_TYPE=MediaType.parse("application/json; charset=utf-8");
  
  public String postContent(String url, Map<String, String> datas) {
    // okHttpClient 实例
    OkHttpClient okHttpClient = new OkHttpClient();
    // 数据对象转换成 json 格式字符串
    String jsonString = JSON.toJSONString(datas);
    //构建RequestBody对象
    RequestBody requestBody = RequestBody.create(JSON_TYPE, jsonString);
    //post方式提交的数据
    Request request = new Request.Builder().url(url).post(requestBody).build();
    // 使用client去请求
    Call call = okHttpClient.newCall(request);
    // 返回结果字符串
    String result = null;
    try {
      // 获得返回结果
      result = call.execute().body().string();
    } catch (IOException e) {
      // 抓取异常
      System.out.println("request " + url + " error . ");
      e.printStackTrace();
    }
    return result;
  }

  public static void main(String[] args) {
    String url ="" ;
    Map<String, String> datas = new HashMap();
    向datas里添加数据
    String content = new JsonPoster().postContent(url,datas);

    System.out.println("API调用结果");
    System.out.println(content);
  }

• // 用 CookieJar 实现 cookie 的存储，便于登录后请求其它 URL 可以复用
    private static final OkHttpClient okHttpClient = new OkHttpClient.Builder()
        .cookieJar(new CookieJar() {
          private final HashMap<String, List<Cookie>> cookieStore = new HashMap<>();
  
          @Override
          public void saveFromResponse(HttpUrl url, List<Cookie> cookies) {
            cookieStore.put("mtime.com", cookies);
            System.out.println("[saveFromResponse]url.host()=" + url.host());
          }
  
          @Override
          public List<Cookie> loadForRequest(HttpUrl url) {
            System.out.println("[loadForRequest]url.host()=" + url.host());
            List<Cookie> cookies = cookieStore.get("mtime.com");
            return cookies != null ? cookies : new ArrayList<>();
          }
        })
        .build();
  

• 文档地址：https://ham.youkeda.com/articles/detail/5f3757fd5e205f30b2c2b1f9

• json格式化工具：http://www.ab173.com/json/jsonviewernew.php

• Headers三大件：

  1. User-Agent浏览器标识

  2. Referer网页标识

  3. Host域名标识

• 写入文本文件

  
  // 文件对象
  File file = new File("foo.txt");
  
  // 写入内容
  FileWriter fileWritter = new FileWriter(file);
  fileWritter.write(content);
  
  // 关闭
  fileWritter.close();
  

• 写入二进制文件

  // 文件对象
  File file = new File("china-city-list.xlsx");
  
  // 写文件
  FileOutputStream fos = new FileOutputStream(file);
  fos.write(data);
  
  // 必须刷新并关闭
  fos.flush();
  fos.close();