Android™

curl with Variable Substitution in a JSON Request Body

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This example shows how to use variables inside a JSON request body using the {{variable_name}} syntax. When the HTTP request’s Content-Type indicates JSON, Chilkat automatically applies proper JSON escaping to each substituted value, ensuring the resulting JSON remains valid. Android™

// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    boolean success = false;

    // Variable names are enclosed between {{ and }}
    // Important: The variable {{var_name}} should be placed inside the quotes.

    // This is correct:
    // curl -X POST https://api.example.com/messages \
    //   -H "Content-Type: application/json" \
    //   -d '{"text":"{{message}}"}'

    // This is incorrect:
    //   -d '{"text":{{message}}}'

    CkStringBuilder sbCurl = new CkStringBuilder();
    sbCurl.AppendLn("curl -X POST https://api.example.com/messages \\");
    sbCurl.AppendLn("  -H \"Content-Type: application/json\" \\");
    sbCurl.AppendLn("  -d '{\"text\":\"{{message}}\"}'");

    CkHttpCurl curl = new CkHttpCurl();

    // In this example, the value we'll provide for the "message" variable
    // will contain chars that require JSON escaping.
    curl.SetVar("message","He said \"Hello, world!\"");

    // To demonstrate how the variables are replaced, this example does not execute the curl command. 
    // Instead, it generates the raw HTTP request that would be sent if the curl command were run.
    CkStringBuilder sbRawRequest = new CkStringBuilder();
    success = curl.ToRawRequest(sbCurl.getAsString(),sbRawRequest);
    if (success == false) {
        Log.i(TAG, curl.lastErrorText());
        return;
        }

    Log.i(TAG, sbRawRequest.getAsString());

    // The output is shown below.
    // Notice that the quote chars around "Hello World!" are properly JSON escaped.

    // POST /messages HTTP/1.1
    // Host: api.example.com
    // Content-Type: application/json
    // Content-Length: 36
    // 
    // {"text":"He said \"Hello, world!\""}

  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}