JCOMMANDER custom annotation and parameter verification function introduction

JCOMMANDER is an open source Java command line parameter analysis framework. It can help developers quickly analyze the command line parameters and use it with custom annotations and parameter verification functions.This article will introduce how to define custom annotations and implement parameter verification in JCOMMANDER. JCOMMANDER custom annotation: 1. First, we need to define a custom annotation to identify parameters that need to be verified.For example, we define a @Range annotation to limit the range of parameter values: @Retention(RetentionPolicy.RUNTIME) @Target(ElementType.FIELD) public @interface Range { int min() default Integer.MIN_VALUE; int max() default Integer.MAX_VALUE; } 2. Then, we can use the annotation in the command line parameter class, for example: public class CommandArgs { @Parameter(names = "-age") @Range(min = 18, max = 60) private int age; // getter and setter } Parameter verification function: 1. After using a custom annotation in the command line parameter class, we can implement the parameter value verification by adding parameter verification logic.In the above example, we use the @Range annotation to limit the AGE parameters. Below is an example of the code verification: public class CommandArgs { @Parameter(names = "-age") @Range(min = 18, max = 60) private int age; // getter and setter public void validate() { if (this.age < 18 || this.age > 60) { throw new ParameterException("Age must be between 18 and 60"); } } } 2. In the main program, we can use JCOMMANDER's value method to trigger parameter verification.For example: public class Main { public static void main(String[] args) { CommandArgs commandArgs = new CommandArgs(); JCommander jCommander = JCommander.newBuilder() .addObject(commandArgs) .build(); jCommander.parse(args); commandArgs.validate(); // Execute other business logic } } In the above example, when we run the program, if the input is not within the range (less than 18 or greater than 60), a parameterexception will be thrown.Therefore, we can ensure the effectiveness of the command line parameters by customize the annotation and parameter verification function. Summarize: Through the custom annotation and parameter verification function of JCOMMANDER, we can add additional verification logic to the command line parameter analysis to ensure the legitimacy of the parameter.This method makes the analysis and verification of command line parameters simple and easy to use, and can be flexibly expanded and customized according to the needs.