How to use the Contract4j5 framework in the Java library
How to use the Contract4j5 framework in the Java library
Contract4j5 is a Java language framework for designing By-Contract, Pre-Condition, Post-Condition, and Invariance Contracts.It can help developers ensure that their code follows specific patterns and specifications, thereby improving the maintenance of code and robustness.This article will introduce how to use the Contract4J5 framework in the Java library.
1. Download and install Contract4J5 framework
First, you need to download the latest version of the framework from the official website of Contract4j5 (https://github.com/Contract4j5/contract4j5).Unzip the downloaded file and add the control4j5 jar file to the class path of your project.
2. Create a Java class library project
Create a new Java -class library project with your favorite IDE (such as Eclipse or Intellij IDEA).
3. Create a Java class
Create a new Java class in the project.This class will contain a way you want to add a contract.
4. Introduce the contract4j5 annotation
In the created Java class, the annotations required to introduce the Contract4J5 framework first.
import org.contract4j5.contract.Contract;
import org.contract4j5.contract.Post;
import org.contract4j5.contract.Pre;
5. Add method and contract
In the Java class, add one or more ways you want to add a contract.
public class MyLibrary {
@Pre ("$ args [0]> 0") // Add the front condition contract to ensure that the parameters are greater than 0
@Post ("$ args [0] == $ result") // Add the rear conditional contract to ensure that the return value is equal to the first parameter
public int add(int a, int b) {
return a + b;
}
@Contract ("Null => False") // Add an unable variable contract to ensure that the empty parameters cannot be introduced
public boolean isNull(String str) {
return str == null;
}
}
6. Configure Contract4J5 parser
Add a file called Contract4J5.properties in your project.In this file, a parser configuring the Contract4J5 framework.
properties
# contract4j5.properties
# Configure the parser, specify the type type that needs to be parsed by each class
org.contract4j5.contract.Contract.instrumentor = org.contract4j5.aspects.CurrentThreadFailFastAndWarnSupplementingRtBraceContract
org.contract4j5.contract.Invar.instrumentor = org.contract4j5.aspects.CurrentThreadFailFastAndWarnSupplementingRtBraceInvar
7. Use Contract4J5 framework
Call the method in the Mylibrary class in your code and ensure that the additional contract is satisfied.
public class Main {
public static void main(String[] args) {
MyLibrary myLibrary = new MyLibrary();
int result = myLibrary.add(2, 3);
System.out.println (result); // Output: 5
boolean isNull = myLibrary.isNull(null);
System.out.println (isnull); // Output: false
}
}
After completing the above steps, your Java library will use the Contract4J5 framework and apply the added contract.When running, any violation of the contract will trigger warnings or abnormalities to help you discover and solve the problem in time.
Note: The code and configuration provided herein are for reference only. The specific implementation may be different due to the project needs and the framework version.Please refer to the official documentation and example code of Contract4j5 for appropriate configuration and adjustment.
