Java访问远程服务

  随着webService的崛起，我们开始中会越来越多的使用到访问远程webService服务。当然对于不同的webService框架一般都有自己的client包供使用，但是如果使用webService框架自己的client包，那么必然需要在自己的代码中引入它的包，如果同时调运了多个不同框架的webService，那么就需要同时引入多个不同的client包，这样做是很烦的。Java本生提供访问远程服务的包，在java.net.*下。接下来我们就用Java原生的package访问webService。

1、发送GET请求

class ReadByGet implements Runnable {
    public void run() {
        try {
            URL url = new URL(
                    "http://fanyi.youdao.com/openapi.do?keyfrom=gusi123123&key=1075925116&type=data&doctype=json&version=1.1&q=hello");//此处访问有道的webService服务，参数都在url中
            URLConnection connection = url.openConnection();//得到一个连接对象
            InputStream is = connection.getInputStream();
            InputStreamReader isr = new InputStreamReader(is, "UTF-8");
            BufferedReader br = new BufferedReader(isr);//用于读取返回的数据流
 
            StringBuffer sb = new StringBuffer();//用于接收返回的数据
            String line = null;
            while ((line = br.readLine()) != null) {
                sb.append(line);
            }
            System.out.println(sb.toString());
            br.close();//关闭各种连接
            isr.close();
            is.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

 2、发送POST请求

class ReadByPost implements Runnable {
    public void run() {
        try {
            URL url = new URL("http://fanyi.youdao.com/openapi.do");//此处通过post访问有道webService
            // URLConnection connection = url.openConnection();
            HttpURLConnection connection = (HttpURLConnection) url
                    .openConnection();//得到一个http的连接对象
            connection.addRequestProperty("encoding", "UTF-8");
            connection.setRequestMethod("POST");//设置请求方式
            connection.setDoInput(true);//设置可写入
            connection.setDoOutput(true);//设置可读取
 
            OutputStream os = connection.getOutputStream();
            OutputStreamWriter osw = new OutputStreamWriter(os, "UTF-8");
            BufferedWriter bw = new BufferedWriter(osw);//定义写入流对象
 
            bw.write("keyfrom=gusi123123&key=1075925116&type=data&doctype=xml&version=1.1&q=hello");
            bw.flush();//通过写入流对象写入请求参数
 
            InputStream is = connection.getInputStream();
            InputStreamReader isr = new InputStreamReader(is, "UTF-8");
            BufferedReader br = new BufferedReader(isr);//定义读取流对象
 
            StringBuffer sb = new StringBuffer();
            String line = null;
            while ((line = br.readLine()) != null) {
                sb.append(line);
            }//通过读取流读取返回数据
 
            //关闭各种连接对象
            br.close();
            isr.close();
            is.close();
            bw.close();
            osw.close();
            os.close();
 
            System.out.println(sb.toString());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

    通过上面也发现使用java原生的package访问webService比较麻烦，然后我们伟大的apache也给我们提供通用的访问webService的jar包，需要的jar包依赖是：（使用到的类在org.apache.http.*）

<dependency>

    <groupId>org.apache.httpcomponents</groupId>

    <artifactId>httpclient</artifactId>

    <version>4.3.6</version>

</dependency>

3、通过httpclient发送GET请求

public class ReadByClientGet implements Runnable {
    HttpClient client = HttpClients.createDefault();
 
    public void run() {
        String uri = "http://www.baidu.com";//访问百度
        HttpGet get = new HttpGet(uri);//得到请求对象
        try {
            HttpResponse response = client.execute(get);//执行访问请求
            HttpEntity entity = response.getEntity();//得到返回数据
            String result = EntityUtils.toString(entity, "UTF-8");//将返回数据输出
            System.out.println(result);
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

 4、通过httpclient发送POST请求

public class ReadByClientPost implements Runnable {
    HttpClient client = HttpClients.createDefault();//创建一个client对象
    public void run() {
        try {
            String uri = "http://fanyi.youdao.com/openapi.do";//post访问有道webService
            HttpPost post = new HttpPost(uri);//得到post请求对象
            //构造请求参数，通过NameValuePair对象（类似于Map集合）
            List<NameValuePair> parameters = new ArrayList<NameValuePair>();
            parameters.add(new BasicNameValuePair("keyfrom", "gusi123123"));
            parameters.add(new BasicNameValuePair("key", "1075925116"));
            parameters.add(new BasicNameValuePair("type", "data"));
            parameters.add(new BasicNameValuePair("doctype", "json"));
            parameters.add(new BasicNameValuePair("version", "1.1"));
            parameters.add(new BasicNameValuePair("q", "java"));
            post.setEntity(new UrlEncodedFormEntity(parameters,"UTF-8"));
 
            HttpResponse response = client.execute(post);//执行post请求，并且接收返回数据
            HttpEntity entity = response.getEntity();
            String result = EntityUtils.toString(entity, "UTF-8");
            System.out.println(result);//输出返回数据
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

     通过上面httpclient只是最简单的基本的访问webService服务。当然还有很多其他细节以及功能可以设计和处理。接下来通过测试方法测试上面的四种访问请求的结果：（输出结果不再粘贴）

public class Main {
    public static void main(String[] args) {
        // new Thread(new ReadByGet()).start();
        // new Thread(new ReadByPost()).start();
        // new Thread(new ReadByClientGet()).start();
        //new Thread(new ReadByClientPost()).start();
    }
}