网络编程的实践

来源：互联网发布：人像摄影技巧知乎编辑：程序博客网时间：2024/05/17 07:16

一个应用程序可能在很多地方要用到网络功能
所以需要把通用的网络操作写到一个公共的类里：
如：

package com.example.networktest;import java.io.BufferedReader;import java.io.InputStream;import java.io.InputStreamReader;import java.net.HttpURLConnection;import java.net.URL;/** * Created by yuwei on 2016/10/5. */public class HttpUtil {    public static String  sendHttpRequest(String address) {        HttpURLConnection connection = null ;        try{            URL url = new URL(address);            connection = (HttpURLConnection) url.openConnection();            connection.setRequestMethod("GET");            connection.setConnectTimeout(8000);            connection.setReadTimeout(8000);            connection.setDoInput(true);            connection.setDoOutput(true);            InputStream in = connection.getInputStream();            BufferedReader reader = new BufferedReader(new InputStreamReader(in));            StringBuilder response = new StringBuilder();            String line;            while ((line = reader.readLine())!=null){                response.append(line);            }            return response.toString();        }catch (Exception e){            e.printStackTrace();            return e.getMessage();        }finally {            if(connection!=null){                connection.disconnect();            }        }    }}

这时调用时：只需要
String address = “http://www.baidu.com”；
String response = HttpUtil.sendHttpRequest（address）；
但是一般网络请求都是耗时操作，这样可能导致，主线程被堵塞

直接在sendHttpRequest（）内部开启一个子线程是不行的，因为耗时是在子线程中进行，sendHttpRequest（）可能在服务器还没响应的时候就已经执行结束了。

所以解决方案是接口的使用
public interface HttpCallbackListener{
void onFinish(String response);
void onError(Exception e);
}
修改原HttpUtil：

package com.example.networktest;import java.io.BufferedReader;import java.io.InputStream;import java.io.InputStreamReader;import java.net.HttpURLConnection;import java.net.URL;/** * Created by yuwei on 2016/10/5. */public class HttpUtil {    public static String  sendHttpRequest(final String address , final HttpCallbackListener listener) {       new Thread(new Runnable() {           @Override           public void run() {               HttpURLConnection connection = null ;               try{                   URL url = new URL(address);                   connection = (HttpURLConnection) url.openConnection();                   connection.setRequestMethod("GET");                   connection.setConnectTimeout(8000);                   connection.setReadTimeout(8000);                   connection.setDoInput(true);                   connection.setDoOutput(true);                   InputStream in = connection.getInputStream();                   BufferedReader reader = new BufferedReader(new InputStreamReader(in));                   StringBuilder response = new StringBuilder();                   String line;                   while ((line = reader.readLine())!=null){                       response.append(line);                   }                  // return response.toString();子线程无法通过return返回数据                   if (listener!=null){                       listener.onFinish(response.toString());                   }               }catch (Exception e){                   e.printStackTrace();                   if (listener!=null){                       listener.onError(e);                   }                 //  return e.getMessage();               }finally {                   if(connection!=null){                       connection.disconnect();                   }               }           }       }).start();    }    public interface  HttpCallbackListener{        void onFinish(String response);        void onError(Exception e);    }}

这时的调用为：
String address = “http://www.baidu.com”；
String response = HttpUtil.sendHttpRequest（address，new HttpCallbackListener（）{
public void onFinish（String response）{
根据返回的内容执行具体的逻辑
}

public void oNError（Exception e）{
对异常情况进行处理
}

}）；

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