elemental2 indexeddb example?

[rhodebump]

I am interested in using indexeddb from within GWT.  I found the following library that indicates that it provides indexeddb support https://github.com/google/elemental2

Does anyone have an example of opening a database? 

Thanks,

Phillip

[Thomas Broyer]

Elemental2 API map directly to the native browser APIs, so you'll start with IndexedDBGlobal.indexedDB and walk your way almost exactly like you'd do in JS.

Javadoc can be found here fwiw: https://javadoc.io/doc/com.google.elemental2/elemental2-indexeddb/1.0.0-RC1

[rhodebump]

Thanks, I did make some progress.   I dug around a little in the javadoc and found the IndexedDbGlobal, which I was able to use to create a new database.

elemental2.indexeddb.IDBFactory indexedDB = elemental2.indexeddb.IndexedDbGlobal.indexedDB;

elemental2.indexeddb.IDBOpenDBRequest openDBRequest = indexedDB.open("mydbtest", 1.0);

So far so good.

With a open database call, I get a returned object of elemental2.indexeddb.IDBOpenDBRequest (https://static.javadoc.io/com.google.elemental2/elemental2-indexeddb/1.0.0-RC1/elemental2/indexeddb/IDBOpenDBRequest.html)

In the google documentation that I have found that describes the indexedDB open operation, https://developers.google.com/web/ilt/pwa/working-with-indexeddb#opening_a_database

They provide the following code:

  var dbPromise = idb.open('test-db2', 1, function(upgradeDb) {
    console.log('making a new object store');
    if (!upgradeDb.objectStoreNames.contains('firstOS')) {
      upgradeDb.createObjectStore('firstOS');
    }
  });

I want to register a function to execute when the database is upgraded.  I see there is a openDBRequest.onupgradeneeded(), but I just can't the syntax right.

elemental2.indexeddb.IDBFactory indexedDB = elemental2.indexeddb.IndexedDbGlobal.indexedDB;

elemental2.indexeddb.IDBOpenDBRequest openDBRequest = indexedDB.open("mydbtest", 1.0);

//how to i call a function for upgrade?  I want to create some object stores.

openDBRequest. onupgradeneeded = doUpgrade();

Thanks for your help.

[Thomas Broyer]

On Monday, January 28, 2019 at 12:49:41 AM UTC+1, rhodebump wrote:

Thanks, I did make some progress.   I dug around a little in the javadoc and found the IndexedDbGlobal, which I was able to use to create a new database.

elemental2.indexeddb.IDBFactory indexedDB = elemental2.indexeddb.IndexedDbGlobal.indexedDB;

elemental2.indexeddb.IDBOpenDBRequest openDBRequest = indexedDB.open("mydbtest", 1.0);

So far so good.

With a open database call, I get a returned object of elemental2.indexeddb.IDBOpenDBRequest (https://static.javadoc.io/com.google.elemental2/elemental2-indexeddb/1.0.0-RC1/elemental2/indexeddb/IDBOpenDBRequest.html)

In the google documentation that I have found that describes the indexedDB open operation, https://developers.google.com/web/ilt/pwa/working-with-indexeddb#opening_a_database

They provide the following code:

  var dbPromise = idb.open('test-db2', 1, function(upgradeDb) {
    console.log('making a new object store');
    if (!upgradeDb.objectStoreNames.contains('firstOS')) {
      upgradeDb.createObjectStore('firstOS');
    }
  });

Note that this is using the IndexedDB Promised library, not the IndexedDB API (see https://developers.google.com/web/ilt/pwa/working-with-indexeddb#comparison_of_indexeddb_api_and_indexeddb_promised_library)

Fwiw, I'd rather use https://developer.mozilla.org/en-US/docs/Web/API/IndexedDB_API as a reference.

 

I want to register a function to execute when the database is upgraded.  I see there is a openDBRequest.onupgradeneeded(), but I just can't the syntax right.

elemental2.indexeddb.IDBFactory indexedDB = elemental2.indexeddb.IndexedDbGlobal.indexedDB;

elemental2.indexeddb.IDBOpenDBRequest openDBRequest = indexedDB.open("mydbtest", 1.0);

//how to i call a function for upgrade?  I want to create some object stores.

openDBRequest. onupgradeneeded = doUpgrade();

That would be something like:

openDBRequest.onupgradeneeded = new OnupgradeneededFn() {
  @Override
  public Object onInvoke(IDBVersionChangeEvent event) {
    doUpgrade();
    return Js.undefined(); // that value will likely be ignored anyway
  }
};

or, using a lambda:

openDBRequest.onupgradeneeded = event -> {
  doUpgrade();
  return Js.undefined();
};