In the actual development process, we often need to call the interface provided by the other party or test whether the interface written by ourselves is suitable. Therefore, the question is, how does Java call the interface? Many projects will encapsulate and specify the interface specifications of their own projects, so most of them need to call the interface provided by the other party or a third-party interface (text messages, weather, etc.). Of course, so does self-testing!

java How to call the interface

1. Open the connection to the url

URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();

2. Set general request attributes

conn.setRequestProperty("accept", "*/*");
conn.setRequestProperty("connection", "Keep-Alive");
conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");

3. Set whether to output to httpUrlConnection and whether to read from httpUrlConnection

In addition, sending a post request must be set. The two most commonly used Http requests are nothing more than get and post. The get request can obtain a static page, or you can put the parameters after the URL string and pass it to the servlet, post and get. The difference is that the post parameters are not placed in the URL string, but in the body of the http request.

conn.setDoOutput(true);
conn.setDoInput(true);

4. Disconnect

It is best to write that disconnect is only cut off when the underlying tcp socket link is idle. If it is being used by other threads, it will not be cut off. If multi-threading is fixed, if you do not disconnect, the number of links will increase until no more information can be sent or received. After writing disconnect, it becomes normal.

conn.disconnect();

Specific implementation code:

package com.c;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;

public class ToInterface {
    /**
     * 調(diào)用對方接口方法
     * @param path 對方或第三方提供的路徑
     * @param data 向?qū)Ψ交虻谌桨l(fā)送的數(shù)據(jù)，大多數(shù)情況下給對方發(fā)送JSON數(shù)據(jù)讓對方解析
     */
    public static void interfaceUtil(String path,String data) {
        try {
            URL url = new URL(path);
            //打開和url之間的連接
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            PrintWriter out = null;
            //請求方式
//          conn.setRequestMethod("POST");
//           //設(shè)置通用的請求屬性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)"); 
            //設(shè)置是否向httpUrlConnection輸出，設(shè)置是否從httpUrlConnection讀入，此外發(fā)送post請求必須設(shè)置這兩個
            //最常用的Http請求無非是get和post，get請求可以獲取靜態(tài)頁面，也可以把參數(shù)放在URL字串后面，傳遞給servlet，
            //post與get的 不同之處在于post的參數(shù)不是放在URL字串里面，而是放在http請求的正文內(nèi)。
            conn.setDoOutput(true);
            conn.setDoInput(true);
            //獲取URLConnection對象對應(yīng)的輸出流
            out = new PrintWriter(conn.getOutputStream());
            //發(fā)送請求參數(shù)即數(shù)據(jù)
            out.print(data);
            //緩沖數(shù)據(jù)
            out.flush();
            //獲取URLConnection對象對應(yīng)的輸入流
            InputStream is = conn.getInputStream();
            //構(gòu)造一個字符流緩存
            BufferedReader br = new BufferedReader(new InputStreamReader(is));
            String str = "";
            while ((str = br.readLine()) != null) {
                System.out.println(str);
            }
            //關(guān)閉流
            is.close();
            //斷開連接，最好寫上，disconnect是在底層tcp socket鏈接空閑時才切斷。如果正在被其他線程使用就不切斷。
            //固定多線程的話，如果不disconnect，鏈接會增多，直到收發(fā)不出信息。寫上disconnect后正常一些。
            conn.disconnect();
            System.out.println("完整結(jié)束");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    public static void main(String[] args) {
        interfaceUtil("http://api.map.baidu.com/telematics/v3/weather?location=嘉興&output=json&ak=5slgyqGDENN7Sy7pw29IUvrZ", "");
//        interfaceUtil("http://192.168.10.89:8080/eoffice-restful/resources/sys/oadata", "usercode=10012");
//        interfaceUtil("http://192.168.10.89:8080/eoffice-restful/resources/sys/oaholiday",
//                    "floor=first&year=2017&month=9&isLeader=N");
    }
}

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