用到的包

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;

GET请求

/**
* 从网络获取json数据,(String byte[})

* @param path
* @return
*/
public static String getJsonByInternet(String path) throws Exception{
    try {
        URL url = new URL(path.trim());
        //打开连接
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

        if(200 == urlConnection.getResponseCode()){
            //得到输入流
            InputStream is =urlConnection.getInputStream();
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            byte[] buffer = new byte[1024];
            int len = 0;
            while(-1 != (len = is.read(buffer))){
                baos.write(buffer,0,len);
                baos.flush();
            }
            return baos.toString("utf-8");
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

POST测试

/**
* POST请求获取数据
*/
public static String postDownloadJson(String path,String post){
    URL url = null;
    try {
        url = new URL(path);
        HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
        httpURLConnection.setRequestMethod("POST");// 提交模式
        // conn.setConnectTimeout(10000);//连接超时 单位毫秒
        // conn.setReadTimeout(2000);//读取超时 单位毫秒
        // 发送POST请求必须设置如下两行
        httpURLConnection.setDoOutput(true);
        httpURLConnection.setDoInput(true);
        // 获取URLConnection对象对应的输出流
        PrintWriter printWriter = new PrintWriter(httpURLConnection.getOutputStream());
        // 发送请求参数
        printWriter.write(post);//post的参数 xx=xx&yy=yy
        // flush输出流的缓冲
        printWriter.flush();
        //开始获取数据
        BufferedInputStream bis = new BufferedInputStream(httpURLConnection.getInputStream());
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        int len;
        byte[] arr = new byte[1024];
        while((len=bis.read(arr))!= -1){
            bos.write(arr,0,len);
            bos.flush();
        }
        bos.close();
            return bos.toString("utf-8");
        } catch (Exception e) {
            e.printStackTrace();
        }
    return null;
}

调用

public static void main(String[] args) {
    String x = postDownloadJson("http://118.89.45.116/Book/index.php/API/GetAllBook/","");
    System.out.println(x);
}