Use the Contract4J5 framework to improve the reliability of the Java class library
Use the Contract4J5 framework to improve the reliability of the Java class library
Summary:
During the software development process, the reliability and correctness of the Java class library are very important.Contract4j5 is a contract -type programming framework that helps developers define and verify the front conditions, rear conditions and class invariance of the Java class library.This article will introduce the use of the Contract4J5 framework and how to improve the reliability of the Java library through it.
1. Pre -conditions
The front conditions refer to some specific conditions that need to be met before the method calls, such as whether the parameters are empty, whether the parameter value is legal, etc.By defining the front conditions, check before the method execution to avoid unnecessary errors and abnormalities.
The following is a sample code fragment, which shows how to use Contract4j5 in the Java class library to define the front conditions:
public class MathUtils {
//@Requires("$1 > 0")
public static int divide(int dividend, int divisor) {
return dividend / divisor;
}
}
In the above example, `` `` `` `$ 1> 0") `specifies the front conditions of the` DIVIDE 'method, that is, the first parameter `dividend` must be greater than zero.If this condition is not met, the method will throw an exception.Using Contract4j5, you can define the front conditions by adding annotations to the method, and automatically check the condition before the method execution.
2. Rear conditions
The rear conditions refer to some properties that are guaranteed after the method call, such as the range of the return value, whether the result meets the expectations, etc.By defining the rear conditions, the execution result of the verification method meets the expectations.
The following is a sample code fragment, which shows how to use Contract4J5 definition rear conditions in the Java class library:
public class MathUtils {
//@Ensures("$1 > 0 && $1 < $2")
public static int findMax(int num1, int num2) {
return num1 > num2 ? num1 : num2;
}
}
In the above example, `@Ensures (" $ 1> 0 && $ 1 <$ 2 ")` specifies the rear conditions of the `FindMax` method, that is, the return value must be greater than zero and less than the transmission.By using Contract4j5, the rear conditions can be defined by adding annotations to the method, and conditional verification is automatically verified after the method execution.
3. Class invariability
Class invariability refers to some properties that always maintain in the life cycle of the instance of the class.By defining the class invariability, the state of the object can not be modified illegally.
The following is a sample code fragment, which shows how to use the Contract4j5 definition class in the Java class library to define the class:
public class Rectangle {
private int width;
private int height;
//@Invariant("$this.width > 0 && $this.height > 0")
public Rectangle(int width, int height) {
this.width = width;
this.height = height;
}
}
In the above example, `@invariant (" $ this.width> 0 && $ this.height> 0 ")` specifies the invariance of the `Rectangle` class, that is, the values of` width` and `height` must be greater than zero.EssenceBy using Contract4j5, the class can be defined by adding an annotation method to the constructor, and conditional inspections are performed during the object creation process.
Summarize:
Using the Contract4J5 framework can help developers improve the reliability of the Java library.By defining and verifying the front conditions, rear conditions, and class invariability, conditional checks can be performed in the process of calling before and after the creation of objects to avoid potential errors and abnormalities.In order to use the Contract4J5 framework, developers need to add the JAR file of the Contract4j5 to the project's dependence, and add corresponding annotations to the classes and methods that need to be used for contract programming.By making full use of the characteristics provided by the Contract4J5 framework, the reliability and correctness of the Java library can be better guaranteed.
