Reputation: 1488

Need to send multiple Volley Requests - in a sequence

I need to use volley to send a request to retrieve a membershipid then pass that membership id into the second volley request to retrieve stats on that member.

I have a problem with my first request working perfectly but the second request seems to start before the variable is returned to be passed. Anyone know how to prevent the second request from starting before value is returned?

Upvotes: 11

Answers (2)

JDOaktown

Reputation: 4467

Code for chaining asynch Volley requests. What's important is:
a) The call to nextRequest() in the mJsonResp listener.
nextRequest() ties each link in the chain together and is called by the listener.
b) The member mLinkedRequest.
c) The abstract function needing override getRequest().
d) How to instantiate ("usage") HTTP requests for registration:

// 1) POST registrations ->  2) PATCH registrations ->  3) GET devices

    pkRequest ChainReg3 = new LinkedRequest(pkURL.devices, null )   {
        @Override public JSONObject getRequest( final JSONObject response ){
        JSONObject retVal = new JSONObject();
        retVal.put( "MyAwesomeString", "This is the final request string in the chain" );
        return retVal;
}
    } ;

    pkRequest ChainReg2 = new LinkedRequest(pkURL.registrations2, ChainReg3  ){
        //pkRequest ChainReg2 = new pkRequest(pkURL.registrations2, null  ){
        @Override public JSONObject getRequest( final JSONObject response ){
        JSONObject retVal = new JSONObject();
        retVal.put( "MyAwesomeInt", 99 );
        return retVal;
    };

    JSONObject firstRequestBodyTest = new JSONObject( "test" );

    pkRequest ChainReg1 = new LinkedRequest(pkURL.registrations, firstRequestBodyTest , ChainReg2  ){
        @Override public JSONObject getRequest( final JSONObject response ){ return null; }
    };

    ChainReg1.submit();
}

/* FYI: I created an enum to deal w/ all the URLs. You may deal w/ them in some other fashion. The point of this post is to show how to chain together asynch volley requests.

package org.Somepackage;


import android.support.annotation.NonNull;
import android.widget.Toast;

import com.android.volley.*;
import com.android.volley.Request.*;
import com.android.volley.Response.ErrorListener;
import com.android.volley.toolbox.JsonObjectRequest;

import org.json.*;
import org.peacekeeper.util.pkUtility;

import java.net.*;
import java.util.*;


public abstract class LinkedRequest{

protected static org.slf4j.Logger mLog;
protected final static pkUtility mUtility = pkUtility.getInstance();
protected final static RequestQueue mRequestQueue = mUtility.getRequestQueue();
protected final static Toast mToast = Toast.makeText( mUtility.getBaseContext(), "", Toast.LENGTH_LONG );

static private HashMap< String, String > newHeader(){
    HashMap< String, String > newHeader = new HashMap<>();
    final String applicationjson = "application/json";

    newHeader.put( "Accept", applicationjson );
    newHeader.put( "Content-Type", applicationjson );
    return newHeader;
}

static private HashMap<String, String> mHeaders = newHeader()
        , registrations2Hdr = newHeader();
static{
    // http://stackoverflow.com/questions/19797842/patch-request-android-volley
    registrations2Hdr.put( "X-HTTP-Method-Override", "PATCH" );
}


//end static


private UUID msg_id = UUID.randomUUID();

//each enum needs priority and method, url, request, response, errlsnr

protected final Response.Listener< JSONObject > mJsonResp =  new Response.Listener< JSONObject >(){
    @Override public void onResponse( JSONObject response ){
        String respStr = "response:\t" + ((response == null)? "NULL" : response.toString() );
        mToast.setText( respStr );
        mToast.show();
        mLog.debug( "onResponse\t url:\t" + mPkURL.toString() + "\t:Response:\t" + respStr );

        nextRequest( response );
    }
};



protected final ErrorListener mErrLsnr = new ErrorListener(){
    @Override public void onErrorResponse( VolleyError error ){
        mToast.setText( "Error:\t" + error.getMessage() );
        mToast.show();
        mLog.error( "Error!:\t" + error.getMessage() );

        if( error.networkResponse != null){
            NetworkResponse response = error.networkResponse;
            int statusCode = error.networkResponse.statusCode;
            mLog.error( "statuscode:\t" + statusCode + ":\t" + new String(response.data) );
        }
    }
};


private HashMap< String, String > getAuthorizationHeader(){
    HashMap< String, String > newHeader = newHeader();
    //newHeader.put( "Authorization", SecurityGuard.getAuthToken() );
    newHeader.put( "Authorization", "test getAuthToken()" );
    mLog.debug( newHeader.toString() );
    return newHeader;
}

//PLACE ALL URL NAMES HERE
public enum pkURL{
    //each link in the chain should be of ever increasing priority to reflect its progression.
    devices(Method.GET, Priority.IMMEDIATE)
    // http://stackoverflow.com/questions/28314160/error-in-volley-patch
    // java.net.ProtocolException: Unknown method 'PATCH'; must be one of [OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE]
    // http://stackoverflow.com/questions/19797842/patch-request-android-volley
    , registrations2( Method.POST, Priority.HIGH, LinkedRequest.registrations2Hdr)
    , registrations(Method.POST, Priority.NORMAL )
    , status
    ;

    //each enum needs priority and method, url, request, response, errlsnr
    protected Priority mPriority;
    protected int mMethod;
    public HashMap< String, String > mHeader;
    protected String URLstr;

    pkURL(){
        mMethod = Method.GET;
        mPriority = Priority.LOW;
        mHeader = LinkedRequest.mHeaders;
    }

    pkURL(int aMethod, Priority aPriority ){
        mMethod = aMethod;
        mPriority = aPriority;
        mHeader = LinkedRequest.mHeaders;
    }

    pkURL(int aMethod,
          Priority aPriority,
          HashMap< String, String > aHeader){
        this(aMethod, aPriority);
        mHeader = aHeader;
    }

}//enum pkURL



public pkURL mPkURL;

private JsonObjectRequest mJsonRequest = null;//The current request of this link. For future Request override getRequest().
private LinkedRequest mLinkedRequest = null;
//This constructor is only used for intermediate and last links in the chain.
public LinkedRequest( @NonNull pkURL aPkURL, LinkedRequest aLinkedRequest ){
    mLog = org.slf4j.LoggerFactory.getLogger( getClass() );
    mPkURL = aPkURL;

    if ( aLinkedRequest != null ){
        mLinkedRequest = aLinkedRequest;
        mLinkedRequest.msg_id = this.msg_id;
    }
}//cstr



//This constructor is  only used for the first link in the chain or singleton requests.
public LinkedRequest( @NonNull final pkURL aPkURL, @NonNull JSONObject aRequestBody, LinkedRequest aLinkedRequest ){
    this( aPkURL, aLinkedRequest );

    try{ aRequestBody.put( "_id", msg_id.toString() ); } catch ( Exception ignore ){}

    mJsonRequest = //this is the current request of this link. For future Requests override getRequest().
    new JsonObjectRequest( aPkURL.mMethod, toURL(), aRequestBody, mJsonResp, mErrLsnr ){
        @Override public Priority getPriority() { return mPkURL.mPriority; }
        @Override public Map<String, String> getHeaders() throws AuthFailureError{ return aPkURL.mHeader; }
    };

    mJsonRequest.setShouldCache( false );
}//cstr


private static final String URLhead = "http://192.168.1.156/";
private String toURL(){ //} throws JSONException{
//private < E extends Enum< E > > URL toURL( E URLPostOrGet ){
    URL url;

    switch ( mPkURL){
    case registrations2:
        this.mPkURL.URLstr = "registrations/" + this.msg_id;
        this.mPkURL.mHeader = registrations2Hdr;
        break;

    case devices:
        final String deviceID = "testdeviceId" //SecurityGuard.getEntry( entryType.deviceId )
                    , keeperID = "testkeeperId" //SecurityGuard.getEntry( entryType.keeperId )
                ;

//GET http://192.168.1.156:80/devices/bbdef07b-9360-4d7b-8448-21c4daca4711?where=keeperId=="b0c486e5-13b1-4555-ba5f-d54bb1f0a6f7"
        this.mPkURL.URLstr = new StringBuilder( "devices/" )
                .append( deviceID )
                .append( "?where=keeperId==\"" )
                .append( keeperID + "\"" )
                .toString();

        this.mHeaders = getAuthorizationHeader();
        break;

    default: this.mPkURL.URLstr = mPkURL.name();
    }//switch

    try{
        url =  new URL(URLhead + this.mPkURL.URLstr + "/" );
    }
    catch ( MalformedURLException e ){
        mLog.error( "Error!:\t" + e.getMessage() );
        url = null;
    }
    return url.toString();
}//toURL


@Override public String toString(){
    String toURL = toURL();

    if (mJsonRequest == null) return "toString() NULL mJsonRequest:\t" + toURL;
    String hdrs;
    try{ hdrs = this.mJsonRequest.getHeaders().toString(); }
    catch ( AuthFailureError aAuthFailureError ){ hdrs = "ERROR: getHeaders()"; }


    return new StringBuilder( "\nmethod:\t:" + mJsonRequest.getMethod() )
            .append( "\nheaders:\t" + hdrs )
            .append( "\nbody:\t" +  new String( mJsonRequest.getBody()) )
            .append( "\nBodyContentType:\t" +  mJsonRequest.getBodyContentType() )
            .append( "\nPriority:\t" +  mJsonRequest.getPriority() )
            .append( "\ngetUrl():\t" +  mJsonRequest.getUrl() )
            .append( "\ntoURL():\t" + toURL )
            .append( "\n" )
            .toString();

}//toString()


//getRequest is used for the FUTURE request of mLinkedRequest.
//for CURRENT request of this() use the constructor
abstract public JSONObject getRequest( final JSONObject response );

private Request nextRequest(final JSONObject aResponse ){//nextRequest() ties each link in the chain together and is called by the listener.
    mLog.debug( "nextRequest:\t" + aResponse.toString() );
    Request retVal = null;
// * * * * * * This is how and where the the "future" request must be called/constructed. * * * * * *
    if ( mLinkedRequest != null ){
        final int mMethod = mLinkedRequest.mPkURL.mMethod;
        final String aURL = mLinkedRequest.toURL();

        final JSONObject requestBody = mLinkedRequest.getRequest( aResponse );

        final Priority priority = mLinkedRequest.mPkURL.mPriority;
        final Map<String, String> header = mLinkedRequest.mPkURL.mHeader;

        this.mJsonRequest = new JsonObjectRequest( mMethod, aURL,
                                                      requestBody,
                                                      mJsonResp, mErrLsnr ){
            @Override public Priority getPriority() { return priority; }
            @Override public Map<String, String> getHeaders() throws AuthFailureError{ return header; }
        };

        mJsonRequest.setShouldCache( false );
        this.mLinkedRequest = mLinkedRequest.mLinkedRequest;
        retVal =  submit();
    }//if
// * * * * * *  * * * * * * * * * * * *  * * * * * * * * * * * *  * * * * * * * * * * * * * * * * * *

return retVal;
}//nextRequest()


public Request submit(){
    mLog.debug( "submit:\n" );
    mLog.debug( this.toString() );
    if ( mLinkedRequest != null ) mLog.debug( "mLinkedRequest:\t" + mLinkedRequest.toString() );
    if ( mJsonRequest!= null ) return mRequestQueue.add( mJsonRequest );
    return null;
}//submit()
}//class LinkedRequest

Upvotes: 0

Angad Tiwari

Reputation: 1768

you can't just write each request sequentially and wait to perform each after each success response ... you have to call second request inside first service response... ie

public void firstServiceCall(String url)
{
      JsonObjectRequest jsonObjReq = new JsonObjectRequest(
            Request.Method.GET, url, null,
            new Response.Listener<JSONObject>() {

                @Override
                public void onResponse(JSONObject response) {
                     int membershipid=response.getInt("membershipid");
                     //suppose the membershipid comes under main json with key "membershipid"
                     secondServiceCall(membershipid,<url2>);
                     // on the response of first service ... call to the second service ... and continue so on... if required
                }
            }, new Response.ErrorListener() {

        @Override
        public void onErrorResponse(VolleyError error) {
        }
    });
    Volley.newRequestQueue(getApplicationContext()).add(jsonObjReq);
  }
  public void secondServiceCall(int membershipid,String url)
  {
       // use this var membershipid acc to your need ... 
       JsonObjectRequest jsonObjReq = new JsonObjectRequest(
            Request.Method.GET, url, null,
            new Response.Listener<JSONObject>() {

                @Override
                public void onResponse(JSONObject response) {
                }
            }, new Response.ErrorListener() {

        @Override
        public void onErrorResponse(VolleyError error) {
        }
    });
    Volley.newRequestQueue(getApplicationContext()).add(jsonObjReq);
  }

also the request call is asynchronous hence... the other process won't wait for service call to finish...hence your second service starts before the first service response

Upvotes: 13

Need to send multiple Volley Requests - in a sequence

Answers (2)

/* FYI: I created an enum to deal w/ all the URLs. You may deal w/ them in some other fashion. The point of this post is to show how to chain together asynch volley requests.

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