HTTP Invoker is a remote communication mechanism in the Spring framework that enables remote communication between Java objects over HTTP. It allows Java objects to invoke methods on remote Java objects, just as if they were local objects. In this article, we will learn how to implement Spring remoting by HTTP Invoker.
Step by Step Implementation
Step 1: Create a Java project in your favorite IDE and add the following dependencies to the pom.xml file:
XML
<!-- Adding spring-context and spring-web dependencies --><dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>5.3.0</version></dependency><dependency> <groupId>org.springframework</groupId> <artifactId>spring-web</artifactId> <version>5.3.0</version></dependency> |
Step 2: Create an interface called CalculatorService.java which will define the methods that can be remotely invoked.
Java
// Define the methods that can be remotely invokedpublic interface CalculatorService { int add(int a, int b); int subtract(int a, int b); int multiply(int a, int b); int divide(int a, int b);} |
Step 3: Create a class called CalculatorServiceImpl.java that implements the CalculatorService interface. This class will be the implementation of remote service.
Java
// Implementation of the remote servicepublic class CalculatorServiceImpl implements CalculatorService { @Override public int add(int a, int b) { return a + b; } @Override public int subtract(int a, int b) { return a - b; } @Override public int multiply(int a, int b) { return a * b; } @Override public int divide(int a, int b) { return a / b; }} |
Step 4: Create a class called HttpInvokerConfig.java that will be used to configure the remote service using the HTTP invoker.
Java
// Configuration of the remote service using HTTP Invoker@Configurationpublic class HttpInvokerConfig { public HttpInvokerServiceExporter httpInvokerServiceExporter(CalculatorService calculatorService) { HttpInvokerServiceExporter exporter = new HttpInvokerServiceExporter(); // Setting the remote service to be exported exporter.setService(calculatorService); // Setting the interface of the remote service exporter.setServiceInterface(CalculatorService.class); return exporter; }} |
Step 5:Create a class called Client.java that will act as a client to the remote service.
Java
// Client to the remote servicepublic class Client { public static void main(String[] args) { // Get the ApplicationContext ApplicationContext context = new ClassPathXmlApplicationContext( "httpInvokerClientContext.xml"); // Get the remote service bean CalculatorService calculatorService = (CalculatorService)context.getBean( "calculatorService"); // Invoke the remote methods System.out.println("Add: " + calculatorService.add(1, 2)); System.out.println( "Subtract: " + calculatorService.subtract(1, 2)); System.out.println( "Multiply: " + calculatorService.multiply(1, 2)); System.out.println( "Divide: " + calculatorService.divide(1, 2)); }} |
Step 6: Create an XML configuration file called applicationContext.xml that will contain the configuration for the client.
XML
<?xml version="1.0" encoding="UTF-8"?> xsi:schemaLocation="http://www.springframework.org/schema/beans <bean id="calculatorService" class="org.springframework.remoting.httpinvoker.HttpInvokerProxyFactoryBean"> <property name="serviceInterface" value="com.neveropen.CalculatorService" /> </bean> </beans> |
Step 7: Run the Client.java class as a Java application and you should see the following output:
Output:
Add: 3 Subtract: -1 Multiply: 2 Divide: 0
Conclusion
In this article, we learned about the Spring HTTP Invoker and how to implement it step by step. We also covered some further subtopics to give you an idea of the various ways in which you can use the Spring HTTP Invoker in your projects.