Decrypted Apache Velocity Engine: How to efficiently process the template in the Java class library

Apache Velocity Engine is a popular Java template engine that can be used to process templates in high efficiency in Java applications.It provides a simple and flexible way to generate dynamic content, thereby reducing the workload of writing a large number of repeated code. The following will introduce how to use Apache Velocity Engine to process the template. 1. Introduce Apache Velocity Engine First, you need to add Apache Velocity Engine to the dependence of the project.It can be implemented by adding the following dependencies in the pom.xml file of the Maven project: <dependency> <groupId>org.apache.velocity</groupId> <artifactId>velocity-engine-core</artifactId> <version>2.4.2</version> </dependency> 2. Create a Velocity engine instance In the Java code, an instance of the Velocity engine needs to be created.You can use the following code to implement: import org.apache.velocity.app.VelocityEngine; import org.apache.velocity.runtime.RuntimeConstants; VelocityEngine velocityEngine = new VelocityEngine(); VelocityEngine.setProperty (RuntimeConstants.runtime_log_logSystem_Class, "ORG.APache.VelOCity.log.nullLLLLOGCHUTE"); velocityEngine.init(); 3. Prepare template Before using Velocity Engine, you need to prepare the template.You can create a template file containing dynamic content and place it in the designated directory of the project.For example, you can create a file called `Template.vm`, and includes the following content: Hello $name! Welcome to Apache Velocity Engine! 4. Fill Once the velocity engine instance and template are ready, you can use the following code to fill the template: import org.apache.velocity.Template; import org.apache.velocity.VelocityContext; // Create velocity context VelocityContext context = new VelocityContext(); context.put("name", "John Doe"); // Get the template Template template = velocityEngine.getTemplate("path/to/template.vm"); // Fill StringWriter writer = new StringWriter(); template.merge(context, writer); String output = writer.toString(); System.out.println(output); In the above code, first created a Velocity context and stored dynamic content in it.Then obtain the template by using the `Gettemplate () method of the Velocity engine instance.Finally, use the `Merge ()` method to fill the data in the context into the template and output the result to the `StringWriter`.In the end, you can get the filled template string from the `StringWriter`. 5. Output results At the end of the above code, you can output the filled template string to the console or write it into the file.In this example, use the `System.out.println (output)` to print the result to the console. Summarize: By using Apache Velocity Engine, you can efficiently process the templates in the Java application.It provides a simple and flexible way to generate dynamic content and reduce the workload of writing lengthy and repeated code.By introducing the steps of Apache Velocity Engine, creating engine instances, preparing templates, filling templates, and output results, you can easily implement the template processing function in the Java class library.