Java发起http请求并解析JSON返回数据

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http 协议

https://www.cnblogs.com/mqy1/p/13884964.html

发起 http 请求并获得返回数据

📑来源

代码源自博客《JAVA如何调用对方http接口得到返回数据》

https://cloud.tencent.com/developer/article/2081582

public String getURLContent(String urlWithNoPara, String para) throws Exception {

    String strURL =  urlWithNoPara + para;
    URL url = new URL(strURL);
    HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
    
    // 设置请求方法
    httpConn.setRequestMethod("GET");

    // POST请求必须设置下面两项
    httpConn.setDoOutput(true);
    httpConn.setDoInput(true);

    httpConn.connect();

    // 读取文件并将内容转换为字符输出
    InputStream inStream = httpConn.getInputStream();
    int n;
    while ((n = inStream.read()) != -1){
        System.out.print((char)n);
    }

    BufferedReader reader = new BufferedReader(new InputStreamReader(httpConn.getInputStream()));
    String line;
    StringBuffer buffer = new StringBuffer();
    while ((line = reader.readLine()) != null) {
        buffer.append(line);
    }
    
    reader.close();
    httpConn.disconnect();
    
    String res = buffer.toString();
    // 输出字符串形式的返回数据
    System.out.println(res);
    
    return res;
}

添加 http 请求头

在前文 HttpURLConnection httpConn = (HttpURLConnection) url.openConnection(); 和 httpConn.connect(); 之间添加以下代码

httpConn.setRequestProperty(key,value); // key 和 value 是你需要添加的头信息的键与值

忽略验证 https 中 SSL 证书

一般用于 SSL 证书失效却又不得不以 https 去请求的情况如报错 java.security.cert.CertificateException: No subject alternative names matching IP address xxx.xxx.xxx.xxx found

在发起 https 请求前调用下文 disableSslVerification() 函数

📑来源

代码源自博客

https://www.cnblogs.com/Springmoon-venn/p/7504901.html

private static void disableSslVerification() {
    try
    {
        // Create a trust manager that does not validate certificate chains
        TrustManager[] trustAllCerts = new TrustManager[] {new X509TrustManager() {
            public java.security.cert.X509Certificate[] getAcceptedIssuers() {
                return null;
            }
            public void checkClientTrusted(X509Certificate[] certs, String authType) {
            }
            public void checkServerTrusted(X509Certificate[] certs, String authType) {
            }
        }
                                                          };

        // Install the all-trusting trust manager
        SSLContext sc = SSLContext.getInstance("SSL");
        sc.init(null, trustAllCerts, new java.security.SecureRandom());
        HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());

        // Create all-trusting host name verifier
        HostnameVerifier allHostsValid = new HostnameVerifier() {
            public boolean verify(String hostname, SSLSession session) {
                return true;
            }
        };

        // Install the all-trusting host verifier
        HttpsURLConnection.setDefaultHostnameVerifier(allHostsValid);
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    } catch (KeyManagementException e) {
        e.printStackTrace();
    }
}

解析 JSON 字符串形式的返回数据

需先在 Maven 的 pom.xml 加上依赖

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.47</version>
</dependency>

后在 Java 中引入包

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;

并在前文 String res = buffer.toString(); 和 return res; 之间添加以下代码

📑来源

代码源自博客

https://blog.csdn.net/qq_43370892/article/details/114805511

    //先转换成JSONObject类型
    JSONObject jsonObj = JSON.parseObject(str);
    //1.通过JSONObject中的getString("key")方法得到对应的值如{"code":"0","error":null,"msg":"success"}这种类型
    System.out.println("code"+jsonObj.getString("code"));

    //2.字符串中含有数组的下文以array为例
    JSONArray jsonInfo = JSONObject.parseArray(jsonObj.getString("array"));//将jsonObj解析成json数组
    for (int i = 0; i < jsonInfo.size(); i++) {//遍历数组
        JSONObject jsonDetailInfo = jsonInfo.getJSONObject(i);//根据下标以此拿数据每一个数组元素又是一个JSONObject对象所以用JSONObject接收
        String x = jsonDetailInfo.getString("x");
        String y = jsonDetailInfo.getString("y");
        //输出当前获取的数据
        System.out.println("x"+x+";y:"+y);
    }