167 posts
From the table above we can see that everything in Scala is an object — there are no primitive types like in Java. Some concepts also differ from Java: Scala includes a few notions of 'nothingness' (Null, null, Nil, Nothing, None, and Unit). Null is a trait (if you're not familiar with traits, think of it as somewhat like an abstract class in Java). There does exist an instance of null.
On the IntelliJ IDEA startup screen, go to Configure → Plugins, type Scala in the search box, and install the Scala plugin; IDEA will ask to restart after installation for the plugin to take effect. Next, create a Scala project: click Create New Project, choose Scala on the left and IDEA on the right, click Next, name the project (here, HelloScala), then pick a storage location. If this is your first build, you'll also need to download the Scala SDK.
Locally the file reads fine, but once packaged as a JAR and uploaded to the server it can't be fetched; the error is: class path resource [xxxx] cannot be resolved to absolute file path because it does not reside in the file system: jar:file:xxxx.jar!/BOOT-INF/classes!xxxx. Enough talk — here's the correct way: use PathMatchingResourcePatternResolver.
Every day we code we face interrupted trains of thought, or pick up today where we left off yesterday. With nothing recorded, we may forget what's left to do, and even lose the solution we had in mind.
Lambda expressions are the most important new feature driving the Java 8 release. They let you pass a function as a parameter to a method (a function passed into a method). So you must upgrade to JDK 8 or above to use Lambda expressions; if you're on JDK 7, you're out of luck.
I ran into this problem while deploying a project at a client's environment. The project's MySQL connection string was localhost, but it errored out saying the database couldn't be connected, and the connection string had been replaced with 127.0.0.1. At first I thought it was a network connectivity issue, so I ran mysql -u root -p and found I could connect fine; ping localhost also resolved to 127.0.0.1. I suspected a mismatched MySQL JDBC driver and swapped countless driver jars, but I was sure it wasn't my program, so I started Googling and found many people with the same situation. I'm summarizing it here for reference. The type of problem I hit was a permissions issue.
Lombok is a third-party Java library. In projects we often define lots of JavaBeans as entity classes, then use IDE shortcuts to generate getter/setter/toString/equals methods — the code looks huge, and worse, renaming requires batch replacement that can go wrong. Lombok can generate that complex yet low-level code at compile time.
Today, for those with no security background, I'll roughly explain how these three types of attacks form. Once you know the principles, you can defend. Since everyone uses different languages and frameworks, this intro focuses on how the attacks form and how to defend — so there's little concrete code; you'll implement it per your own situation.
After learning Git, many of you are eager to act — you have opinions on open source projects, or you've found bugs and optimizations. But how do you contribute your code to an open source project? Today I'll show you how to share your code elegantly.
The essence of Git is branch management. If everyone edits on the master branch, the project falls into chaos, so a workflow is needed to ensure normal development — the focus of this article. First, a simple diagram:
