Jakarta Expression Language API's Guide in Java Library

Jakarta Expression Language (Jel) is a powerful expression language standard for processing and value for expression of expression in the Java library.This article will provide you with the guidelines of the use of JAKARTA Expression Language API in the Java library, including complete programming code and related configuration. Introduction Jakarta Expression Language (Jel) is part of the Java EE specification. It provides a standard expression language for processing dynamic data and dynamic computing in Java applications.Jel is very suitable for embedding dynamic expressions into static code, making the code more flexible and configurable. Second, configuration To use Jel in the Java library, you need to include the following dependencies in the construction path of the project: Maven： <dependency> <groupId>javax.el</groupId> <artifactId>javax.el-api</artifactId> <version>3.0.0</version> </dependency> <dependency> <groupId>org.glassfish.web</groupId> <artifactId>javax.el</artifactId> <version>3.0.0</version> </dependency> Gradle： groovy implementation 'javax.el:javax.el-api:3.0.0' implementation 'org.glassfish.web:javax.el:3.0.0' Third, use Jakarta Expression Language API Below is a simple example, showing how to use Jel in the Java class library: 1. Import related classes: import javax.el.ExpressionFactory; import javax.el.ValueExpression; import javax.el.ELContext; import javax.el.StandardELContext; 2. Create an ExpressionFactory instance: ExpressionFactory factory = ExpressionFactory.newInstance(); 3. Create an expression string: String expressionString = "${name}"; 4. Create an EL context: ELContext context = new StandardELContext(factory); 5. Compile the expression string to ValueExpression: ValueExpression expression = factory.createValueExpression(context, expressionString, String.class); 6. Set related variables: String name = "Zhang San"; context.setVariable("name", factory.createValueExpression(name, String.class)); 7. Value expression and output results: String result = (String) expression.getValue(context); System.out.println ("Result:" + Result); Fourth, complete example code Below is a complete example, showing how to use Jakarta Expression Language API in the Java library to express the value: import javax.el.ExpressionFactory; import javax.el.ValueExpression; import javax.el.ELContext; import javax.el.StandardELContext; public class JakartaExpressionLanguageExample { public static void main(String[] args) { // Create ExpressionFactory instance ExpressionFactory factory = ExpressionFactory.newInstance(); // Create an expression string String expressionString = "${name}"; // Create EL context ELContext context = new StandardELContext(factory); // Compile expressions as valueExpression ValueExpression expression = factory.createValueExpression(context, expressionString, String.class); // Set variables String name = "Zhang San"; context.setVariable("name", factory.createValueExpression(name, String.class)); // Value expression and output results String result = (String) expression.getValue(context); System.out.println ("Result:" + Result); } } In this example, we created a simple expression `$ {name}`, use Jel to find the value of the variable `name` and print the result. The above is the guideline of Jakarta Exposition Language API in the Java library.By using Jel, you can more flexibly and dynamically handle expression computing and value, making Java applications more convenient and efficient when processing dynamic data.