google datastore Insert Date as null value using java

Question

package com.example.guestbook;

import com.google.appengine.api.datastore.DatastoreService;
import com.google.appengine.api.datastore.DatastoreServiceFactory;
import com.google.appengine.api.datastore.Entity;

import java.io.IOException;
import java.util.Date;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 Key addTask(String description, DateTime receiveddate) {
             Key key = datastore.allocateId(keyFactory.newKey());
          Entity task = Entity.newBuilder(key)
            .set("description", StringValue.newBuilder(description).
      setExcludeFromIndexes(true).build())
            .set("receiveddate",(receiveddate))    
            .set("created", DateTime.now())
            .set("done", false)
         .build();
        datastore.put(task);
    return key;
     }
    void handleCommandLine(String commandLine) {
    String[] args = commandLine.split("\\s+");

    if (args.length < 1) {
      throw new IllegalArgumentException("not enough args");
    }

    String command = args[0];
    switch (command) {
      case "new":

        args = commandLine.split("\\s+", 3);
        if (args.length != 3) {
          throw new IllegalArgumentException("missing description");
        }
        addTask(args[1],DateTime.copyFrom());
        System.out.println("task added");
        break;
     public static void main(String[] args) throws Exception {
    TaskList taskList = new TaskList();
    System.out.println("Cloud Datastore Task List");
    System.out.println();
    printUsage();
    while (true) {
      String commandLine = System.console().readLine("> ");
      if (commandLine.trim().isEmpty()) {
        break;
      }
      try {
        taskList.handleCommandLine(commandLine);
      } catch (IllegalArgumentException e) {
        System.out.println(e.getMessage());
        printUsage();
      }
    }
    System.out.println("exiting");
    System.exit(0);
   }

    private static void printUsage() {
    System.out.println("Usage:");
    System.out.println();
    System.out.println("  new <description>  Adds a task with a description         <description>");
     System.out.println("  done <task-id>     Marks a task as done");
     System.out.println("  list               Lists all tasks by creation time");
     System.out.println("  delete <task-id>   Deletes a task");
       System.out.println();
     }
    }

Trying to insert DateTime field as 0 or null value for a partiular record While using Google Cloud Datastore, I need to insert a few records into the database with NULL as the date value. I've tried different ways but it is reflecting errors in inserting. /*

  As per this link  https://github.com/GoogleCloudPlatform/java-docs-samples/blob/master/datastore/src/main/java/com/google/datastore/snippets/TaskList.java

Answer 1

Updates since latest edits

(I do not think the code in your latest update will compile, but ignoring that... :-) )

Are you sure these are the correct imports (I am referring to the APIs for appengine-api-1.0-sdk-1.9.24)?

Your example uses:

import com.google.appengine.api.datastore.DatastoreService;
import com.google.appengine.api.datastore.DatastoreServiceFactory;
import com.google.appengine.api.datastore.Entity;

However you seem to be coding to a different API (perhaps the low-level external API). This is meant for use outside appengine, it might work but it might be easier if you just use the regular appengine api as I showed in my original answer below (Notice I am using setProperty not set).

Overlooking the above, I suspect that in these lines:

.set("receiveddate",(receiveddate))    
.set("created", DateTime.now())

you should have used a value builder as you did in this line:

.set("description", StringValue.newBuilder(description).

I believe you are using the com.google.cloud.datastore API. Try using NullValue see below:

// beware untested code!
import com.google.cloud.datastore.Datastore;
import com.google.cloud.datastore.DatastoreOptions;
import com.google.cloud.datastore.DateTime;
import com.google.cloud.datastore.Entity;
import com.google.cloud.datastore.KeyFactory;
import com.google.cloud.datastore.NullValue;

Datastore datastore =
        DatastoreOptions.getDefaultInstance().getService();
KeyFactory keyFactory = datastore.newKeyFactory().setKind("Dummy");
Entity.Builder entity0 = Entity.newBuilder(keyFactory.newKey("abc"));
DateTime receiveddate = null /* or some other value */;
entity0.set("receiveddate", receiveddate == null ? NullValue.of() : receiveddate);
entity0.set("created", DateTime.now());

Original Answer

This seems to work. Just invoke the handler and then see the two entities in the datastore viewer (tested on dev_appserver):

package com.example.guestbook;

import com.google.appengine.api.datastore.DatastoreService;
import com.google.appengine.api.datastore.DatastoreServiceFactory;
import com.google.appengine.api.datastore.Entity;

import java.io.IOException;
import java.util.Date;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class GuestbookServlet extends HttpServlet {
    @Override
    public void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws IOException {
        DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
        Entity entity0 = new Entity("Dummy", "abc");
        entity0.setProperty("created", new Date());
        datastore.put(entity0);
        Entity entity1 = new Entity("Dummy", "xyz");
        entity1.setProperty("created", null);
        datastore.put(entity1);
    }
}

Is there something fundamentally different about what you are doing?