Creating HTTP Post

[Alan Blass]

Hi! I am creating a HTTP Post using the following code:

import java.io.*;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.omg.CORBA.NameValuePair;

public class VodComms {
    public static void main(String[] args) {
        List<NameValuePair> formparams = new ArrayList<NameValuePair>();
        formparams.add(new NameValuePair("param1", "value1"));
        formparams.add(new NameValuePair("param2", "value2"));
        UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formparams, "UTF-8");
        
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost("http://localhost/myproject/");
        try {
            httpclient.execute(httpPost);
        } catch (ClientProtocolException ex) {
            Logger.getLogger(VodComms.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IOException ex) {
            Logger.getLogger(VodComms.class.getName()).log(Level.SEVERE, null, ex);
        }

    }
}

But on line 23, it says: cannot find symbol: httpclient.execute().
Also on line 16 and 17, also cannot find symbol: for constructor NameValuePair().

What is the correct way of creating the HTTP post?

Can someone help?

Thanks.

[Ulf Dittmer]

You are importing the wrong NameValuePair class - look at the package name.

Declare the client object as DefaultHttpClient, not HttpClient (which has abstract methods only).

[Christophe Verré]

There's an example at HttpClient homepage. It's a GET, but you should be able to figure out how to change it for POST.

[Alan Blass]

Hi Christophe,

Your example is on version 3.1. Now is version 4.0.3. They are different.

Hi Ulf,

I have only 2 options:
1) org.omg.CORBA.NameValuePair
2) org.omg.DynamicAny.NameValuePair

which one is it? I have tried both, both gave me errors. I have also tried:

formparams.add(new BasicNameValuePair("param1", "value1"));
But it says cannot find symbol.

I thought I have already declared the client object as DefaultHttpClient?
HttpClient httpclient = new DefaultHttpClient();

Please advise. Thanks.

[Rob Spoor]

Line 23 should work, as HttpClient has a method execute(HttpUriRequest request) and HttpPost implements HttpUriRequest.

NameValuePair has two constructors. One takes no arguments, the other takes a String and an org.omg.COBRA.Any. You are providing two Strings. So you need to wrap that second String into an Any. Unfortunately, I see no sub classes for Any so you'll need to create one yourself.

Edit: indeed the wrong NameValuePair. But that would make me think the creation of entity would already cause an error. Odd...

[Ulf Dittmer]

Your example is on version 3.1. Now is version 4.0.3. They are different.

Yup, the 4.x URL is http://hc.apache.org/. Somewhere around there are tutorials and code examples.

formparams.add(new BasicNameValuePair("param1", "value1"));
But it says cannot find symbol.

That's the one. Which import did you add to your code?

I thought I have already declared the client object as DefaultHttpClient?
HttpClient httpclient = new DefaultHttpClient();

You created a DefaultHttpClient object, but you declared it to be HttpClient.

[Rob Spoor]

Ulf Dittmer wrote:Declare the client object as DefaultHttpClient, not HttpClient (which has abstract methods only).

What about declaring against interfaces? I wouldn't declare it as DefaultHttpClient unless I needed to call methods not declared in HttpClient.

[Alan Blass]

Rob Prime wrote:Line 23 should work, as HttpClient has a method execute(HttpUriRequest request) and HttpPost implements HttpUriRequest.

errmm...it is still giving me "cannot find symbol". Am I right to say that I cast httpPost into HttpUriRequest to make it work?

NameValuePair has two constructors. One takes no arguments, the other takes a String and an org.omg.COBRA.Any. You are providing two Strings. So you need to wrap that second String into an Any. Unfortunately, I see no sub classes for Any so you'll need to create one yourself.

Edit: indeed the wrong NameValuePair. But that would make me think the creation of entity would already cause an error. Odd...

How do I wrap the second String into an Any?

Please advise. Thanks.

[Christophe Verré]

Alan Blass wrote:
errmm...it is still giving me "cannot find symbol". Am I right to say that I cast httpPost into HttpUriRequest to make it work?

Are you compiling with the right JARs in your classpath ? Aren't there any older libraries somewhere ?

(sorry for posting a link to the old library)

[Rob Spoor]

Alan Blass wrote:

Rob Prime wrote:Line 23 should work, as HttpClient has a method execute(HttpUriRequest request) and HttpPost implements HttpUriRequest.

errmm...it is still giving me "cannot find symbol". Am I right to say that I cast httpPost into HttpUriRequest to make it work?

Update your libraries. I downloaded version 4.0.3, made changes to the declaration and instantiation of NameValuePair, and it compiled successfully. Well, apart from an uncaught exception.

NameValuePair has two constructors. One takes no arguments, the other takes a String and an org.omg.COBRA.Any. You are providing two Strings. So you need to wrap that second String into an Any. Unfortunately, I see no sub classes for Any so you'll need to create one yourself.

Edit: indeed the wrong NameValuePair. But that would make me think the creation of entity would already cause an error. Odd...

How do I wrap the second String into an Any?

I you've read my update you'd seen that you used the wrong NameValuePair, and I looked at this wrong one. You need to import org.apache.http.NameValuePair instead, and instantiate as org.apache.http.message.BasicNameValuePair:

        formparams.add(new BasicNameValuePair("param1", "value1"));
        formparams.add(new BasicNameValuePair("param2", "value2"));

After this the creation of entity still fails because an uncaught exception but the other lines compile just fine.

[Alan Blass]

Hi Rob,

I have checked and my libraries are httpclient-4.0.3.jar and httpmime-4.0.3.jar for this project.

The httpclient.execute(httpPost); is still giving me "cannot find symbol". Any ideas?

The formparams.add(new BasicNameValuePair("param2", "value2")); is also giving me "cannot find symbol".

But formparams.add(new NameValuePair("param1", "value1")); is not.

Please advise. Thanks.

[Rob Spoor]

Did you add all dependencies of HttpClient as well? I'm missing httpcore there, which is definitely in the ZIP file with the dependencies.

[Ulf Dittmer]

Post the list of import statements. Make sure all classes you're using are covered by those imports, and that none of them is from the org.omg.CORBA.* hierarchy.

[Alan Blass]

Hi!

I downloaded the HttpClient and the dependencies:
Library Files:

httpclient-4.0.3.jar
httpmime-4.0.3.jar
apache-mime4j-0.6.jar
commons-codec-1.3.jar
commons.logging-1.1.1.jar
httpcore-logging-1.1.1.jar

httpclient.execute(httpPost); now works.

My source code now:

import java.io.*;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.NameValuePair;

public class VodComms {
    public static void main(String[] args) {
        List<NameValuePair> formparams = new ArrayList<NameValuePair>();
        formparams.add(new BasicNameValuePair("param1", "value1"));
        formparams.add(new BasicNameValuePair("param2", "value2"));        

        DefaultHttpClient httpclient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost("http://localhost/");
        try {
            UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formparams, "UTF-8");
            httpclient.execute(httpPost);
        } catch (ClientProtocolException ex) {
            Logger.getLogger(VodComms.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IOException ex) {
            Logger.getLogger(VodComms.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

But on line 15 and 16, it says "cannot find symbol". Am I missing something here?

In addition, how should I use entity on line 21?

Thanks.

[Ulf Dittmer]

But on line 15 and 16, it says "cannot find symbol". Am I missing something here?

Yes, the import statement for BasicNameValuePair. Note that it's in a different package than NameValuePair.

[Alan Blass]

Hi!

How about line 21?

Thanks

[Alan Blass]

Found it:

httpPost.setEntity(entity);