java通过java.net.URL发送http请求调用接口

一般在*.html,*.jsp页面中我们通过使用ajax调用接口,这个是我们通常用的。对于这些接口，大都是本公司写的接口供自己调用，所以直接用ajax就可以。但是，如果是多家公司共同开发一个东西，一个功能可能要调多个接口，一两个ajax可以在jsp页面上显示,但是如果多了,就不能写这么多ajax在前端了。这时候需要封装一成一个接口，在接口里面如何调用其他接口呢？这就用到了java.net.URL这个类。

java.net.URL用法如下

　　　　 BufferedReader in=null;
        java.net.HttpURLConnection conn=null;
        String msg = "";// 保存调用http服务后的响应信息
        try
        {
　　　　　　  //实例化url
            java.net.URL url = new java.net.URL(path);
　　　　　　　//根据url获取HttpURLConnection
            conn = (java.net.HttpURLConnection) url.openConnection();
　　　　　　　//设置请求的参数
            conn.setRequestMethod("POST");
            conn.setConnectTimeout(5 * 1000);// 设置连接超时时间为5秒 
            conn.setReadTimeout(20 * 1000);// 设置读取超时时间为20秒 
            conn.setDoOutput(true);    // 使用 URL 连接进行输出，则将 DoOutput标志设置为 true
            conn.setDoInput(true);
            conn.setRequestProperty("Content-Type", "text/xml;charset=UTF-8");
            //conn.setRequestProperty("Content-Encoding","gzip");
            conn.setRequestProperty("Content-Length", String.valueOf(params.length()));  //设置请求内容(长度)长度
            OutputStream outStream = conn.getOutputStream();   // 返回写入到此连接的输出流
            outStream.write(params.getBytes());    //将参数写入流中
            outStream.close();//关闭流

            if (conn.getResponseCode() == 200) {
                // HTTP服务端返回的编码是UTF-8,故必须设置为UTF-8,保持编码统一,否则会出现中文乱码
                in = new BufferedReader(new InputStreamReader((InputStream) conn.getInputStream(), "UTF-8"));
                msg = in.readLine();
            }
        }catch(Exception ex)
        {
            ex.printStackTrace();
        }finally
        {
            if(null!=in)
            {
                in.close();
            }
            if(null!=conn)
            {
                conn.disconnect();
            }
        }
        return msg;

HttpUtil工具类 

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import java.net.HttpURLConnection;
import java.net.URL;


/**
 * http工具
 *
 */
public final class HttpUtil {
    /**
     * 模拟http协议发送get请求
     **/
    public static String sendGetRequest(String url) {
        String result = "";
        InputStream in = null;

        HttpURLConnection connection = null;

        try {
            URL httpUrl = new URL(url);
            connection = (HttpURLConnection) httpUrl.openConnection();
            connection.setRequestProperty("accept", "*/*");
            connection.setRequestProperty("Charset", "UTF-8");
            connection.setRequestProperty("connection", "Keep-Alive");
            connection.setRequestProperty("user-agent",
                "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            connection.setRequestMethod("GET");
            connection.connect();

            if (connection.getResponseCode() == 200) {
                in = connection.getInputStream();

                ByteArrayOutputStream bs = new ByteArrayOutputStream();
                int n = 0;
                byte[] datas = new byte[2048];

                while ((n = in.read(datas)) != -1) {
                    bs.write(datas, 0, n);
                }

                bs.flush();
                result = new String(bs.toByteArray(), "utf-8");
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
            try {
                if (in != null) {
                    in.close();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }

            try {
                connection.disconnect();
            } catch (Exception ex) {
            }
        }

        return result;
    }

    /**
    * 模拟http协议发送post请求
    **/
    public static String sendPostRequest(String url, String param) {
        InputStream in = null;
        String result = "";
        HttpURLConnection connection = null;

        try {
            URL httpUrl = new URL(url);
            connection = (HttpURLConnection) httpUrl.openConnection();
            connection.setRequestProperty("accept", "*/*");
            connection.setRequestProperty("Charset", "UTF-8");
            connection.setRequestProperty("connection", "Keep-Alive");
            connection.setRequestProperty("user-agent",
                "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            connection.setRequestMethod("POST");
            connection.setDoOutput(true);
            connection.setDoInput(true);
            connection.setUseCaches(false);
            connection.getOutputStream().write(param.getBytes("utf-8"));
            connection.getOutputStream().flush();

            if (connection.getResponseCode() == 200) {
                in = connection.getInputStream();

                ByteArrayOutputStream bs = new ByteArrayOutputStream();
                int n = 0;
                byte[] datas = new byte[2048];

                while ((n = in.read(datas)) != -1) {
                    bs.write(datas, 0, n);
                }

                bs.flush();
                result = new String(bs.toByteArray(), "utf-8");
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
            try {
                if (in != null) {
                    in.close();
                }
            } catch (IOException ex) {
                ex.printStackTrace();
            }

            try {
                connection.disconnect();
            } catch (Exception ex) {
            }
        }

        return result;
    }

    /**
     * 普通post文件上传
     */
    public static String upLoadAttachment(String url, String fileName, File file) {
        String result = null;

        HttpURLConnection connection = null;
        BufferedReader reader = null;

        try {
            URL httpUrl = new URL(url);
            connection = (HttpURLConnection) httpUrl.openConnection();
            connection.setRequestProperty("accept", "*/*");
            connection.setRequestProperty("Charset", "UTF-8");
            connection.setRequestProperty("connection", "Keep-Alive");
            connection.setRequestProperty("user-agent",
                "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            connection.setRequestMethod("POST");
            connection.setConnectTimeout(5000);
            connection.setReadTimeout(5000);
            connection.setDoOutput(true);
            connection.setDoInput(true);
            connection.setUseCaches(false);

            String bound = "----------" + System.currentTimeMillis();
            connection.setRequestProperty("Content-Type",
                "multipart/form-data; boundary=" + bound);

            StringBuilder sb = new StringBuilder();
            sb.append("--");
            sb.append(bound);
            sb.append("
");
            sb.append("Content-Disposition: form-data;name="" + fileName +
                "";filename="" + file.getName() + ""
");
            sb.append("Content-Type:application/octet-stream

");

            byte[] data = sb.toString().getBytes("utf-8");
            OutputStream out = new DataOutputStream(connection.getOutputStream());
            out.write(data);

            DataInputStream in = new DataInputStream(new FileInputStream(file));
            int bytes = 0;
            byte[] bufferOut = new byte[1024];

            while ((bytes = in.read(bufferOut)) != -1) {
                out.write(bufferOut, 0, bytes);
            }

            in.close();

            byte[] foot = ("
--" + bound + "--
").getBytes("utf-8"); // 定义最后数据分隔线
            out.write(foot);
            out.flush();
            out.close();

            InputStream inn = connection.getInputStream();
            ByteArrayOutputStream bs = new ByteArrayOutputStream();
            int n = 0;
            byte[] datas = new byte[2048];

            while ((n = inn.read(datas)) != -1) {
                bs.write(datas, 0, n);
            }

            bs.flush();
            result = new String(bs.toByteArray(), "utf-8");

            return result;
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
            try {
                connection.disconnect();
            } catch (Exception ex) {
            }
        }

        return null;
    }
    
   /**
     * post文件上传 - 使用InputStream输入流(例如MultipartFile从前端获取文件后转发给其他的服务器)
     */
    public static String upLoadAttachment(String url,String keyName, String fileName, InputStream fins) {
        String result = null;

        HttpURLConnection connection = null;
        BufferedReader reader = null;

        try {
            URL httpUrl = new URL(url);
            connection = (HttpURLConnection) httpUrl.openConnection();
            connection.setRequestProperty("accept", "*/*");
            connection.setRequestProperty("Charset", "UTF-8");
            connection.setRequestProperty("connection", "Keep-Alive");
            connection.setRequestProperty("user-agent",
                    "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            connection.setRequestMethod("POST");
            connection.setConnectTimeout(5000);
            connection.setReadTimeout(5000);
            connection.setDoOutput(true);
            connection.setDoInput(true);
            connection.setUseCaches(false);

            String bound = "----------" + System.currentTimeMillis();
            connection.setRequestProperty("Content-Type",
                    "multipart/form-data; boundary=" + bound);

            StringBuilder sb = new StringBuilder();
            sb.append("--");
            sb.append(bound);
            sb.append("
");
            sb.append("Content-Disposition: form-data;name="" + keyName +
                    "";filename="" + fileName + ""
");
            sb.append("Content-Type:application/octet-stream

");

            byte[] data = sb.toString().getBytes("utf-8");
            OutputStream out = new DataOutputStream(connection.getOutputStream());
            out.write(data);

            DataInputStream in = new DataInputStream(fins);
            int bytes = 0;
            byte[] bufferOut = new byte[1024];

            while ((bytes = in.read(bufferOut)) != -1) {
                out.write(bufferOut, 0, bytes);
            }

            in.close();

            byte[] foot = ("
--" + bound + "--
").getBytes("utf-8"); // 定义最后数据分隔线
            out.write(foot);
            out.flush();
            out.close();

            InputStream inn = connection.getInputStream();
            ByteArrayOutputStream bs = new ByteArrayOutputStream();
            int n = 0;
            byte[] datas = new byte[2048];

            while ((n = inn.read(datas)) != -1) {
                bs.write(datas, 0, n);
            }

            bs.flush();
            result = new String(bs.toByteArray(), "utf-8");

            return result;
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
            try {
                connection.disconnect();
            } catch (Exception ex) {
            }
        }

        return null;
    }
}