JAKARTA Expression Language API Skill

JAKARTA Expression Language API Skill Overview: Jakarta Expression Language (Jexl) is a powerful tool for performing dynamic expression on the Java platform.It provides a simple and flexible way to make dynamic expressions more efficient when developing the Java class library.This article will introduce some techniques to use Jakarta Expression Language API to help you improve the efficiency of the development of the Java library. 1. Introduce the Jexl library: First, you need to introduce the Jexl library into your project.You can complete this step by adding the following dependencies to the Maven project: <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-jexl3</artifactId> <version>3.0</version> </dependency> 2. Create a JEXL engine instance: Before using the Jexl API, you need to create a Jexl engine instance.This can be completed in the following ways: import org.apache.commons.jexl3.*; JexlEngine jexl = new JexlBuilder().create(); 3. Expressive expression: Jexl API allows you to execute dynamic expression.In order to execute a expression, you need to create a Jexl expression object for the expression and execute it through an engine instance.The following is a simple example: String expression = "2 * (a + b)"; JexlExpression jexlExpression = jexl.createExpression(expression); // Create a jexl context (for the value of storage variables) JexlContext context = new MapContext(); context.set("a", 5); context.set("b", 3); // Express the expression and get the result Object result = jexlExpression.evaluate(context); System.out.println (result); // Output results: 16 4. The method of visiting the Java library: Jexl API also allows you to access the Java class library in the expression.You can achieve it by adding the Java library object to the context of the Jexl.The following is an example: import java.util.List; import org.apache.commons.jexl3.*; public class MyLibrary { public static List<String> getNames() { // Return to some name lists } } // Add the Mylibrary class to Jexl context JexlContext context = new MapContext(); context.set("lib", new MyLibrary()); // Dominate mylibrary.getNames method in the expression String expression = "lib.getNames()"; JexlExpression jexlExpression = jexl.createExpression(expression); // Express the expression and get the result Object result = jexlExpression.evaluate(context); List<String> names = (List<String>) result; in conclusion: Using Jakarta Expression Language API can bring a lot of convenience to the development of the Java library.By providing dynamic expression execution functions, you can make your class library more flexible and easy to use.The techniques described in this article are just the tip of the iceberg of the Jexl API. You can also find more powerful functions by understanding the API, thereby further improving the efficiency of the Java class library development. I hope this article will be helpful for your application in the development of the Java library!