Category: Tech Notes

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MongoDB Java Driver notes

A few notes on using the MongoDB Java Driver API:

Getting a connection:

MongoClient client = new MongoClient("localhost", 27017);
DB db = client.getDB("test");

Get a collection from connected db:

DBCollection collection = db.getCollection("example");

 

Find all docs in collection and iterate through results:

DBCursor c = collection.find();
try {
   while(c.hasNext()) {
       System.out.println(c.next());
   }
} finally {
   c.close();
}

 

Simple findOne query, matching a doc with properyname = value:

DBObject result = collection.findOne(new BasicDBObject("propertyname", "value"));

 

Find all, sort on property ‘example’ ascending (1=asc, -1=desc), and limit to 10 results:

DBCursor c = collection.find()
    .sort(new BasicDBObject("example", 1))
    .limit(10);

 

Serialize results of a cursor to JSON (tip from here):

JSON json = new JSON();
String jsonString = json.serialize(c);
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WildFly 8.2 WELD-001408 Unsatisfied Dependencies error

If you see an error like this:

WELD-001408: Unsatisfied dependencies for type [typename] with qualifiers @Default
at injection point [BackedAnnotatedField] @Inject [propertyname]

… then you’re probably missing a default beans.xml file to initialize CDI in the container. The file doesn’t need to contain anything else than this:

<?xml version="1.0"?>
<beans xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://jboss.org/schema/cdi/beans_1_0.xsd" />

and drop it in /META-INF/ or /WEB-INF/

More info here and here.

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MongoDB install on a Mac

By default MongoDB uses /data/db as it’s location for databases. You need to create this dir and then chown it to the user running mongod. For example:

sudo chown username /data/db

More info here.

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AngularJS Tutorial – notes (1)

Random notes from following through the AngularJS tutorial here.

My first time (several months back) working through part of the tutorial I struggled getting node.js up and running on Windows. Useful thread and comments on this post here.

Installing on Mac OS X, no problems.

Useful Tutorial Steps – Tools Install and Setup

(not intended to be a comprehensive set of steps, just mainly for myself to backtrack and see what I’ve done so far in the tutorial)

Install git (already have)

Clone the tutorial source project:

git clone --depth=14 https://github.com/angular/angular-phonecat.git

Download and install node.js from here.

npm install – install the development tools.Note: the tutorial is not specific where you run this, but you must run this inside the clones angular-phonecat dir.

Useful scripts setup with the tutorial project:

  • npm start : start a local development web-server
  • npm test : start the Karma unit test runner
  • npm run update-webdriver : install the drivers needed by Protractor (run this once, and first before running Protractor)
  • npm run protractor : run the Protractor end to end (E2E) tests

Interesting note: no issue with the default config on Mac OS X and running the dev server on port 8000. This was an issue on my Windows machine and needed to change the default port to something other than 8000.

Errors Starting npm run protractor

All the other scripts ran first time for me, but protractor would not start, giving an error about ELIFECYCLE. Seems similar to this issue. I ran these to steps:

npm update
npm run update-webdriver

but then the error changed to something more verbose, about couldn’t find an .exe file:

util.puts: Use console.log instead
Using ChromeDriver directly...
[launcher] Error: Could not find chromedriver at /Users/kev/angularjs/angular-phonecat/node_modules/protractor/selenium/chromedriver.exe

A quick Google found this issue, and the steps described by jpaljasma fixed the issue:

  • edited package.json in the root of the tutorial project, changed devDependencies.protractor to be “*”, removed node_modules, ran npm install and npm run update-webdriver

Now the e2e tests supplied with the project run as expected.

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