Source Code : Method Replacement Example

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Method Replacement Example

/*
Pro Spring
By Rob Harrop
Jan Machacek
ISBN: 1-59059-461-4
Publisher: Apress
*/



///////////////////////////////////////////////////////////////////////////////////////
//File: replacement.xml
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
    <bean id="methodReplacer" class="FormatMessageReplacer"/>
    <bean id="replacementTarget" class="ReplacementTarget">
        <replaced-method name="formatMessage" replacer="methodReplacer">
            <arg-type>String</arg-type>
        </replaced-method>
    </bean>
    <bean id="standardTarget" class="ReplacementTarget"/>
</beans>


///////////////////////////////////////////////////////////////////////////////////////

public class ReplacementTarget {

    public String formatMessage(String msg) {
        return "<h1>" + msg + "</h1>";
    }
    
    public String formatMessage(Object msg) {
        return "<h1>" + msg + "</h1>";
    }
    
    public void foo() {
        
    }
}

///////////////////////////////////////////////////////////////////////////////////////
import java.lang.reflect.Method;

import org.springframework.beans.factory.support.MethodReplacer;

public class FormatMessageReplacer implements MethodReplacer {

    public Object reimplement(Object target, Method method, Object[] args)
            throws Throwable {

        if (isFormatMessageMethod(method)) {

            String msg = (String) args[0];

            return "<h2>" + msg + "</h2>";
        } else {
            throw new IllegalArgumentException("Unable to reimplement method "
                    + method.getName());
        }
    }

    private boolean isFormatMessageMethod(Method method) {

        // check correct number of params
        if (method.getParameterTypes().length != 1) {
            return false;
        }

        // check method name
        if (!("formatMessage".equals(method.getName()))) {
            return false;
        }

        // check return type
        if (method.getReturnType() != String.class) {
            return false;
        }

        // check parameter type is correct
        if (method.getParameterTypes()[0] != String.class) {
            return false;
        }

        return true;
    }

}


///////////////////////////////////////////////////////////////////////////////////////
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.FileSystemResource;
import org.springframework.util.StopWatch;

public class MethodReplacementExample {

    public static void main(String[] args) {
        BeanFactory factory = new XmlBeanFactory(new FileSystemResource(
                "build/replacement.xml"));

        ReplacementTarget replacementTarget = (ReplacementTarget) factory
                .getBean("replacementTarget");
        ReplacementTarget standardTarget = (ReplacementTarget) factory
                .getBean("standardTarget");

        displayInfo(replacementTarget);
        displayInfo(standardTarget);
    }

    private static void displayInfo(ReplacementTarget target) {
        System.out.println(target.formatMessage("Hello World!"));

        StopWatch stopWatch = new StopWatch();
        stopWatch.start("perfTest");

        for (int x = 0; x < 1000000; x++) {
            String out = target.formatMessage("foo");
        }

        stopWatch.stop();

        System.out.println("1000000 invocations took: "
                + stopWatch.getTotalTimeMillis() + " ms");
    }
}
           
       

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