Java Consume REST API

Description: Java Consume REST API (GET/POST/PUT/DELETE)

Imports

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

Url Connection

Need add throws declaration or surround with try/catch;

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

Sets the general request property. If a property with the key already exists, overwrite its value with the new value.

RequestMethod:

GET;
POST;
PUT;
DELETE;

conn.setRequestProperty("Accept", "application/json");
conn.setRequestProperty("Content-Type", "application/json");
conn.setRequestMethod("POST");

To enable Output (Request Body) setting: true

If your request requires a body, the default RequestMethod is POST;

conn.setDoOutput(true);

To enable Output (Response Body) setting: true

conn.setDoInput(true);

When a request requires a body (request Body) it is necessary to use OutputStreamWriter to send the data.

OutputStreamWriter output = new OutputStreamWriter(conn.getOutputStream());
output.write(resquestBody.toString());
output.flush();

Gets the status code from an HTTP response message.

conn.getResponseCode()
conn.getResponseMessage()

Output

Status: 200 - OK

When a request receives a body (response Body), it is necessary to use the InputStreamReader to receive the data.

InputStreamReader input = new InputStreamReader(conn.getInputStream());
BufferedReader br = new BufferedReader(input);
String line = null;
StringBuilder responseBody = new StringBuilder();
responseBody.append("responseBody:\n");
while ((line = br.readLine()) != null) {
    responseBody.append("\t" + line + "\n");
}

When finished, just disconnect the connection.

conn.disconnect();

Java Consume REST API

Url Connection

Code snippet

Exceptions

Some links for more in depth learning