How to Call Web Service in Android Using SOAP

Introduction

 

In this tutorial, we will learn how to call a Web Service using SOAP (Simple Object Access Protocol).

 

Prerequisites

 

Web Service, SOAP envelope, WSDL (Web Service Definition Language)

 

What is SOAP?

 

SOAP is a protocol specification for exchanging structured information in the implementation of Web Services in computer networks. It relies on Extensible Markup Language (XML) for its message format and usually relies on other Application Layer protocols, most notably Hypertext Transfer Protocol (HTTP) and Simple Mail Transfer Protocol (SMTP), for message negotiation and transmission. The following is the structure of the SOAP Envelope:

 

 

Step 1

 

First, create a "New Android Project". Name it "WebServiceDemo" like below.

 

 

 

 

Step 2

 

Now right-click on your "WebServiceDemo" project and select "New -> Folder"

 

 

Now, give it a name it "lib". We need to add a SOAP library into this directory.

 

 

Step 3

 

Now download the attached library named "ksoap2-android-assembly-2.6.0-jar-with-dependencies.jar". Copy that file and paste it into the "lib" directory.

 

After copying, do the following steps:

1. Right-click on the project.
2. Go "Build Path -> Configure Build Path"
     
    
3. Now, click on "Add Jars" and select the ".jar" file from the "project -> lib" directory.
    
    
4. Click on "Ok" to finish the procedure of adding the library to the Android application.

Step 4

 

Next, we need to create a layout of a screen. To do so, go to "WebServiceDemo -> res -> layout -> main.xml"

Open this XML file in editing mode, and place the below code.

 

Main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Fahrenheit"
        android:textAppearance="?android:attr/textAppearanceLarge" />
    <EditText
        android:id="@+id/txtFar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
        <requestFocus />
    </EditText>
    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Celsius"
        android:textAppearance="?android:attr/textAppearanceLarge" />
    <EditText
        android:id="@+id/txtCel"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <LinearLayout
        android:id="@+id/linearLayout1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
        <Button
            android:id="@+id/btnFar"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="0.5"
            android:text="Convert To Celsius" />
        <Button
            android:id="@+id/btnCel"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="0.5"
            android:text="Convert To Fahrenheit" />
    </LinearLayout>
    <Button
        android:id="@+id/btnClear"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Clear" />
</LinearLayout>

This will create simple following screen.

 

 

Step 5

 

Now, find out any Web Service, make sure that you can view its WSDL file by writing "?wsdl" after that address.

 

For example, you have a web service like http://www.w3schools.com/webservices/tempconvert.asmx",  so to view the WSDL file, simply write "?wsdl" after this address like:

 

http://www.w3schools.com/webservices/tempconvert.asmx?WSDL". 

 

You are now done with the Web Service part from the internet. Now you need to extend some portion of the WSDL file. Open the first link in your browser, it will display 2 conversions for you: 

• CelsiusToFahrenheit
• FahrenheitToCelsius

Select anyone of them, and you will see following screen:

 

 

For CelsiusToFahrenheit

1. SOAP_ACTION = "http://tempuri.org/CelsiusToFahrenheit";
2. NAMESPACE = "http://tempuri.org/";
3. METHOD_NAME = "CelsiusToFahrenheit";
4. URL = "http://www.w3schools.com/webservices/tempconvert.asmx?WSDL";

For FahrenheitToCelsius

1. SOAP_ACTION = "http://tempuri.org/FahrenheitToCelsius";
2. NAMESPACE = "http://tempuri.org/";
3. METHOD_NAME = " FahrenheitToCelsius ";
4. URL = "http://www.w3schools.com/webservices/tempconvert.asmx?WSDL";

Step 6

 

You need to understand some classes before proceeding to use a Web Service.

1. SoapObject (

   A simple dynamic object that can be used to build SOAP calls without implementing KvmSerializable. Essentially, this is what goes inside the body of a SOAP envelope - it is the direct subelement of the body and all further sub-elements. Instead of this class, custom classes can be used if they implement the KvmSerializable interface.

    

   Constructor

   SoapObject (java.lang.String namespace, java.lang.String method)

    
2. SoapSerializationEnvelope

   This class extends the SoapEnvelope with Soap Serialization functionality.

    

   Constructor

   SoapSerializationEnvelope (int version)

    

     Fields

   Type	Field	Description
   boolean	dotNet	Set this variable to true for compatibility with what seems to be the default encoding for .Net-Services.

   Methods

   Return Type	Method Name	Description
   void	setOutputSoapObject(java.lang.Object soapObject)	Assigns the object to the envelope as the outbound message for the soap call.

3. HttpTransportSE (org.ksoap2.transport.HttpTransportSE)

   A J2SE based HTTP transport layer.
    

   Constructor

   HttpTransportSE(java.lang.String url)

    

   Method

   Return Type	Method	Description
   void	call(java.lang.String SoapAction, SoapEnvelope envelope)	set the desired soapAction header field

Step 7

 

Open your "WebServiceDemo -> src -> WebServiceDemoActivity.java" file and enterr following code.

 

WebServiceDemoActivity.java

import org.ksoap2.SoapEnvelope;
import org.ksoap2.serialization.SoapObject;
import org.ksoap2.serialization.SoapSerializationEnvelope;
import org.ksoap2.transport.HttpTransportSE;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class WebServiceDemoActivity extends Activity
{
    /** Called when the activity is first created. */
    private static String SOAP_ACTION1 = "http://tempuri.org/FahrenheitToCelsius";
    private static String SOAP_ACTION2 = "http://tempuri.org/CelsiusToFahrenheit";
    private static String NAMESPACE = "http://tempuri.org/";
    private static String METHOD_NAME1 = "FahrenheitToCelsius";
    private static String METHOD_NAME2 = "CelsiusToFahrenheit";
    private static String URL = "http://www.w3schools.com/webservices/tempconvert.asmx?WSDL";
    Button btnFar,btnCel,btnClear;
    EditText txtFar,txtCel;
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        btnFar = (Button)findViewById(R.id.btnFar);
        btnCel = (Button)findViewById(R.id.btnCel);
        btnClear = (Button)findViewById(R.id.btnClear);
        txtFar = (EditText)findViewById(R.id.txtFar);
        txtCel = (EditText)findViewById(R.id.txtCel);
        btnFar.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                //Initialize soap request + add parameters
                SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME1);
                //Use this to add parameters
                request.addProperty("Fahrenheit",txtFar.getText().toString());
                //Declare the version of the SOAP request
                SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);
                envelope.setOutputSoapObject(request);
                envelope.dotNet = true;
                try {
                        HttpTransportSE androidHttpTransport = new HttpTransportSE(URL);
                        //this is the actual part that will call the webservice
                        androidHttpTransport.call(SOAP_ACTION1, envelope);
                        // Get the SoapResult from the envelope body.
                        SoapObject result = (SoapObject)envelope.bodyIn;
                        if(result != null)
                        {
                              //Get the first property and change the label text
                              txtCel.setText(result.getProperty(0).toString());
                        }
                        else
                        {
                              Toast.makeText(getApplicationContext(), "No Response",Toast.LENGTH_LONG).show();
                        }
                  } catch (Exception e) {
                        e.printStackTrace();
                  }
                  }

            });
        btnCel.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                //Initialize soap request + add parameters
                SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME2);
                //Use this to add parameters
                request.addProperty("Celsius",txtCel.getText().toString());
                //Declare the version of the SOAP request
                SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);
                envelope.setOutputSoapObject(request);
                envelope.dotNet = true;
                try {
                        HttpTransportSE androidHttpTransport = new HttpTransportSE(URL);
                        //this is the actual part that will call the webservice
                        androidHttpTransport.call(SOAP_ACTION2, envelope);
                        // Get the SoapResult from the envelope body.
                        SoapObject result = (SoapObject)envelope.bodyIn;
                        if(result != null)
                        {
                              //Get the first property and change the label text
                              txtFar.setText(result.getProperty(0).toString());
                        }
                        else
                        {
                              Toast.makeText(getApplicationContext(), "No Response",Toast.LENGTH_LONG).show();
                        }
                  } catch (Exception e) {
                        e.printStackTrace();
                  }
                  }
            });
        btnClear.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                txtCel.setText("");
                txtFar.setText("");
            }
        });
    }
}

Step 8

 

Now, open your "WebServiceDemo -> android.manifest" file. Add the following line before the <application> tag:

 

<uses-permission android:name="android.permission.INTERNET" />

 

This will allow the application to use the internet.

 

Step 9

 

Run your application in the Android Cell. You will get the following outcome:

 

Note

In the emulator, we need to fix a proxy, so try the application in an Android Cell.

 

 

Summary

 

In this brief tutorial, we learned about Web Services, SOAP envelopes, WSDL files, HTTP transport, and how to use them in an Android application.