Use the Contract4J5 framework to implement contract verification in the Java class library
Use the Contract4J5 framework to implement contract verification in the Java class library
Overview:
Contract is a technology that verification and assertion method calls are verified and asserted during the development process.By adding a contract to the code, we can ensure that the input and output of the method meet the limits and conditions defined in advance.Contract4j5 is a Java library that provides us with a simple and convenient way to implement contract verification.This article will introduce how to use Contract4J5 to implement contract verification in the Java class library.
step:
1. Import contract4j5 library:
First, we need to import the Contract4j5 library.You can introduce the library by adding the following dependencies in the construction configuration file of the project:
<dependency>
<groupId>org.codehaus.contract4j5</groupId>
<artifactId>contract4j5</artifactId>
<version>1.8.1</version>
</dependency>
2. Create a contract interface:
Next, we need to create a contract interface.The contract interface defines some methods for implementation according to specific needs.The parameters and return values of these methods will be used to verify the contract.
public interface MyContract {
@Contract
void validateInput(String param);
@Contract
String validateOutput(int result);
}
3. Create implementation class:
Now we can create a class to implement the contract interface.In this category, we need to use the annotations of the Contract4j5 to add a contract to the method.
public class MyClass implements MyContract {
@Override
public void validateInput(@NotNull String param) {
// Add contract verification logic
Contract.assertpRecondition (Param! = Null, "The parameters cannot be empty!");
Contract.assertpRecondition (param.length ()> 0, "The length of the parameter must be greater than 0!");
}
@Override
public String validateOutput(@Min(0) int result) {
// Add contract verification logic
Contract.assertpostCondition (Result> 0, "The output must be greater than 0!");
Return "contract verification successfully!";;
}
}
4. Create a test class:
Finally, we can create a test class to verify the contract.In the test class, we need to create a contract verification device and use it to execute the contract.
public class Main {
public static void main(String[] args) {
MyContract myClass = new MyClass();
Contract4J5.configure();
// Create a contract verification device
ContractEnforcer contractEnforcer = new ContractEnforcer();
// Execute contract verification
contractEnforcer.enforceContract(myClass);
}
}
explain:
-The contract interface in Step 2 defines two methods: ValidateInput and ValidateoutPut.These methods use the @Contract annotation of the Contract4j5 library to implement the input and output contract verification constraints.
-MyClass in Step 3 implements contract interfaces, and uses the contract.assertprecondition and contract.AssertpostCondition method to add contract verification logic using the contract.asSserTPRECONDITINDITINDITION and ContractpReCondition.
-The test class in Step 4 creates an instance of the implementation class and is equipped with the Contract4j5 library.Then, the Enforcecontract method is used to perform contract verification by creating the Contractnforceer object and calling the ENFORCECONTRACT method.
Summarize:
Using the Contract4j5 library can easily implement contract verification in the Java class library.By defining the contract interface and the annotation of using the Contract4j5 library, we can verify and assess the input and output of the method during the development process.This helps improve the reliability and maintenance of code.
