Spring dependency injections

Here's my list of handy links that I found useful when learning about dependency injections in Spring.

Spring documentation: The IoC container

StackOverflow: Why is my Spring @Autowired field null?

StackOverflow: Spring: Why is setter not called in spite of @Autowired annotation

StackOverflow: Spring @Autowired and Singletons

StackOverflow: How does autowiring work in Spring?

StackOverflow: Spring constructor injection shows null When accessing it on methods

StackOverflow: Singleton and @Autowired returning NULL

Baeldung: Guide to Spring @Autowired

Reflectoring.io: Why You Should Use Constructor Injection in Spring

More of Less blog by Steve Claridge: Two reasons why your Spring @Autowired component is null

Writing: What is the "argument"?

When I was reading about how to improve my thesis writing, I often saw things like:

• be clear about your argument
• delete whatever doesn't address your argument
• add signposts around your argument
• you should design the structure of your paper around your argument

... but I was always like: "WTF is the argument?"  I knew what my thesis statement was:  It was the last sentence of my first paragraph.  It was the main point of the paper in a single sentence.  But what was my argument?

Finally, I came across this beautiful explanation in Bad Choices by Ali Almossawi:  "An argument is made up of a set of statements known as propositions, each of which may be true or false."

Ah, ha!  OK!   So if my thesis statement is like a question, then my argument is the fleshed out answer.  It is a set of propositions (facts), each of which I would explain and elaborate on and relate to what others have said.  I get it!!!

Topic sentences

The best advice I ever received about thesis writing was to structure my paragraphs around topic sentences.  The phrase "topic sentence" makes it sound like it should be polished for a good copy, but that isn't necessarily so.  Even in the beginning when all you write is crap, I've found that using topic sentences helps structure your thinking.

The topic sentence is the first sentence of the paragraph and should should state the point of the paragraph.  The rest of the sentences in the paragraph will link back to the first point to support it or expand on it.

In the early phases of writing, your topic sentences help you to cluster your nebulous thoughts into actual shapes.  It's OK to write a topic sentence that is crappy and that will never actually appear in the final thesis.  Don't let your fear of errors interrupt this early writing.  The point is to get your thoughts out so they can grow and be shaped by your other thoughts as those get written down, too. 

You can worry about making your topic sentences all nice and fitting with your thesis outline later, when you're editing or polishing.

During thesis editing, your topic sentences become little "hooks" that you can use to think of your thesis in larger chunks.  Being able to think of your thesis in chunks will make it easier to wrap your head around the whole thing.  You can mentally grab onto the chunks in your mind.

Inevitably, at some point you're going to need to restructure the whole thing.  You might change your thesis focus, or your supervisor might realize that your point could be better conveyed if explained from a new angle.  When that happens, you'll be grateful that you've left yourself "hooks" to grasp on to!

Hurrah for topic sentences!

New admin profile, Mac OS X

Recently I had to create a new user on my Mac.  Here are some commands I used to transfer ownership to my new account:

sudo chown -R $(whoami) /usr/local
sudo chown root:wheel /usr/local

Eclipse taking forever to start

A couple times now, when I've started Eclipse (I'm using Eclipse neon), the startup screen is displayed for a very long time and Eclipse just doesn't start up.  To fix it, just delete the *.snap file.  (full path below)

The last time I was at my computer, it hadn't shut down properly.  It was the last day before the long weekend - Thanks giving weekend!  There I was, wearing my hat and coat, standing up at my desk, waiting for my computer to log out before I left.  I was jumping up and down, "come on, I'm late, I'm late, I'm late!" But the stupid thing would not log out, even though I had selected "Log out" or "shut down" a few times already.  So I was like "screw you, I have to pick up my kid," and I hit the power button.  Maybe not the best thing to do, but, sorry, I don't have a choice here. 

A few days later, here I am, and Eclipse won't start.  The solution?  Delete the .snap file.  It is located in:

workspace/.metadata/.plugins/org.eclipse.core.resources/*.snap

Delete that file, then Eclipse should actually start next time.  If that doesn't work, one time I found I also had to delete a few other .snap and .history files in

WORKSPACE/.metadata/.plugins/org.eclipse.core.resources/.projects/LAST_PROJ_BEFORE ECLIPSE_CRASHED

.


see:
https://stackoverflow.com/questions/3657054/eclipse-freezing-at-startup-before-loading-workspace

SQL 'limit' the number of results in Hibernate

In my java application, I use Hibernate to access objects from the database.  For queries, I often use the Criteria classes.  One time, I needed to apply a limit to a query because I only wanted to show the top 5 objects, then provide the user to a link to another page with full results, if they wanted more. 

So, to apply the limit to my Criteria query, I went:

criteria.setFirstResult(0).setMaxResults(5);

However, I noticed that my page was now only showing the top 2 results.  I was well aware that there were more than 2 results.  Why wasn't it showing 5?  I had set the limit to 5, but why was it only giving me 2 objects?

It turns out that it was because my query was joining with other tables, and the limit of 5 was being applied to some of the intermediate joins along the way.

I learned how to fix it from theotherian's post about the problem.  I love the title: hibernate, joins, and max results: a match made in hell .  In summary, to solve the problem, I had to make a change to my model object.  In my case, the model object is Event.java because my query was returning a List of Event objects.

Throughout Event.java, I looked for all the attributes that were joined with other objects (tables).  Basically, everywhere I had used @OneToMany.  For each of these attributes, beneath the
@OneToMany annotation, I added two more annotations.  First, I changed the fetch mode to SELECT  (so, add this annotation:  @Fetch(FetchMode.SELECT).  Second, I set the batch size to 2 (add this annotation: @BatchSize(size = 2)).

This fixed my problem.  Running the query again, it was now returning my top 5 instead of some mysteriously lower number.

Data mining, Stats, etc.

'Just came across a cool link and wanted to file it somewhere.  I thought I already had a blog post to gather up links like this, but I can't find it.  Oh well.

Seeing Theory