A good Design-by-Contract library for Java? [closed]

Answer 1

I'd highly recommend you to consider the Java Modeling Language (JML).

Answer 2

I think that many DbC libraries were surclassed by the builtin assert keyword, introduced since Java 1.4:

• it is a built-in, no other library is required
• it works with inheritance
• you can activate/deactivate on package basis
• easy to refactoring (e.g. no assertions in comments)

Answer 3

I would suggest a combination of a few tools:

• Java's assert condition... or it's more advanced Groovy cousin, Guava's Preconditions.checkXXXX(condition...) and Verify.verify(condition...), or a library like AssertJ, if all you need is just to do simple checks in your 'main' or 'test' code

• you'll get more features with a tool like OVal; it can check both objects as well as method arguments and results, you can also fire checks manually (eg to show validation errors on UI before a method is called). It can understand existing annotations eg from JPA or javax.validation (like @NotNull, @Pattern, @Column), or you can write inline constraints like @Pre(expr="x >= 0 && x <= y"). If the annotation is @Documented, the checks will be also visible in Javadocs (you don't have to describe them there as well).

• OVal uses reflection, which can make performance issues and other problems in some environments like Android; then you should consider tool like Google's Cofoja, which has less functionality, but depends on compile-time Annotation Processing Tool instead of reflection

Answer 4

It's been a long time since I've looked at these, but found some old links. One was for JASS.

The other one that I had used (and liked) was iContract by Reliable Systems. It had an ant task that you would run as a preprocessor. However, I can't seem to find it with some google searches, it looks like it has vanished. The original site is now a link farm. Check out this link for some possible ways to get to it.

Answer 5

There is a Groovy extensions that enables Design by Contract(tm) in Groovy/Java code - GContracts. It uses so-called closure annotations to specify class invariants, pre- and postconditions. Examples can be found on the project's github wiki.

Major advantage: it is only a single jar without external dependencies and it can be resolved via Maven compliant repositories since its been placed in the central Maven repo.

Answer 6

I tested contract4J one time and found it usable but not perfect. You are creating contracts for for and after method calls and invars over the whole class.

The contract is created as an assertion for the method. The Problem is that the contract itself is written in a string so you don't have IDE support for the contracts or compile time cheching if the contract still works.

A link to the library