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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