Learn from the Jakarta Expression Language API in the Java class library

Know the Java class library of JAKARTA Expression Language API (referred to as Jexl) Introduction: Jakarta Expression Language API (Jexl) is an open source library for expressing and manipulating objects for expressions in Java applications.It is part of the Jakarta EE project, which is used to simplify the process of using Java developers to use expressions in applications.Jexl provides a simple and powerful expression language that allows developers to operate and manipulate objects by writing short and easy -to -understand expressions. Features: -It is easy to use: Jexl grammar is simple and clear, easy to understand and learn.It borrows Java's syntax and extends some additional operators and functions, providing more powerful expression ability. -Dimalism: Jexl supports variables and method calls of dynamic types.This means that developers do not need to declare variables or methods in advance, and can dynamically operate and manipulate objects during runtime. -The powerful expression support: Jexl provides rich expression functions, including arithmetic operations, logical operations, conditional expression, regular expression, etc.Developers can read, calculate and modify the objects through these expressions. -The scalability: Jexl uses an insertable architecture to allow developers to define their own operators and functions to meet specific needs. Example code: Here are some examples of Jexl API to help readers better understand their usage. 1. Create a Jexl expression engine: JexlEngine jexlEngine = new JexlBuilder().create(); 2. Analyze and execute the expression: JexlExpression expression = jexlEngine.createExpression("foo + bar"); JexlContext context = new MapContext(); context.set("foo", 10); context.set("bar", 20); Object result = expression.evaluate(context); System.out.println (result); // Output results: 30 3. Definition custom function: public class MyFunctions { public static Integer add(Integer a, Integer b) { return a + b; } } // Register a custom function JexlEngine jexlEngine = new JexlBuilder().namespaces(Collections.singletonMap("myFunctions", MyFunctions.class)).create(); // Use a custom function JexlExpression expression = jexlEngine.createExpression("myFunctions:add(foo, bar)"); JexlContext context = new MapContext(); context.set("foo", 10); context.set("bar", 20); Object result = expression.evaluate(context); System.out.println (result); // Output results: 30 in conclusion: Jakarta Expression Language API (Jexl) is a powerful and easy -to -use Java class library for expressing and manipulating objects for expressions in Java applications.By using Jexl, developers can handle expressions more flexible and efficiently, thereby improving development efficiency.Regardless of the simple value calculation or complex object operation, Jexl can meet the needs of developers and help them better realize the logic of Java applications.