SpringBoot java reflection example

Jan 16, 2017

If you want to call a method in a spring bean, and the method’s name is unknown, you should use java reflection to call the method.

1. Pom.xml

Here we use spring boot 1.4.3

<dependencyManagement>
    <dependencies>
        <dependency>
            <!-- Import dependency management from Spring Boot -->
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>1.4.3.RELEASE</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

2. Define two spring beans

Here we define two beans:

The first bean is the server bean, which would call the second bean’s method by reflection
The second bean is the bean to be called by the server bean, supply some methods to be called

@Component("Server")
public class Server {
	@Autowired
    private ApplicationContext appContext;//Here we inject the spring app context for later use.

}
@Component("MethodsBean")
public class MethodsBean {
	public void aMethod() {
		System.out.println("test");
	}
}

3. Use java reflection to call the MethodsBean’s any method

Now it’s the trick:

String methodName = "aMethod"; // the method to be called

Object bean = appContext.getBean("MethodsBean");//defined by the @Component params

Method method = bean.getClass().getMethod(methodName);
if (method != null) {
    return (Integer) method.invoke(bean);//java reflection here.

} else {
    //print error message.

}

The core steps are as follows:

use appContext to get the bean object
use methodName as the param to search for the Method object
if got the method object, then use java reflection to invoke the method

You can find detail documents about the springboot and java reflection here: