Spring autowired...pass source class to autowired class - spring

Question

Caught up in a weird requirement. I need to attach unique error id to log4j message and return that message id back to interface.So, I though lets create a spring service, like this
public class LoggingService {
protected static Logger logger = LoggerFactory.getLogger(LoggingService.class);
public String debug(String debug_msg)
{
String uniqueMsgId = generateUniqueId();
logger.debug(concatIdWithMsg(uniqueMsgId, debug_msg));
return uniqueMsgId;
}
}
and autowired this to wherever i need it.
public class LoginLogoutController {
#Autowired
LoggingService logger;
#RequestMapping(value = "/login", method = RequestMethod.GET)
public String getLoginPage()
{
logger.debug("Login page requested");
}
}
Although it worked fine, but the source class in logger msg is LoggingService which is obvious. What i want is to pass the class in which LoggingService is autowired so that the logger message shows the original source of problem. I tried somehow to change the service
but got no further idea how to pass source class
public class LoggingService<T> {
protected static Logger logger = null;
Class<T> sourceClass;
public void construct(Class<T> sourceClass)
{
this.sourceClass = sourceClass;
logger = LoggerFactory.getLogger(sourceClass);
}
public String debug(String debug_msg)
{
String uniqueMsgId = generateUniqueId();
logger.debug(concatIdWithMsg(uniqueMsgId, debug_msg));
return null;
}
}

Answer 1

I used this mechanism to inject a logger.
Create this annotation..
/**
* Indicates InjectLogger of appropriate type to
* be supplied at runtime to the annotated field.
*
* The injected logger is an appropriate implementation
* of org.slf4j.Logger.
*/
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
#Retention(RUNTIME)
#Target(FIELD)
#Documented
public #interface InjectLogger {
}
Now lets define a class that actually does the job of injecting the logger implementation.
/**
* Auto injects the underlying implementation of logger into the bean with field
* having annotation <code>InjectLogger</code>.
*
*/
import java.lang.reflect.Field;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.util.ReflectionUtils;
import static org.springframework.util.ReflectionUtils.FieldCallback;
public class LoggerInjector implements BeanPostProcessor {
public Object postProcessAfterInitialization(Object bean, String beanName)
throws BeansException {
return bean;
}
public Object postProcessBeforeInitialization(final Object bean,
String beanName) throws BeansException {
ReflectionUtils.doWithFields(bean.getClass(), new FieldCallback() {
public void doWith(Field field) throws IllegalArgumentException,
IllegalAccessException {
// make the field accessible if defined private
ReflectionUtils.makeAccessible(field);
if (field.getAnnotation(InjectLogger.class) != null) {
Logger log = LoggerFactory.getLogger(bean.getClass());
field.set(bean, log);
}
}
});
return bean;
}
}
Using it is even simpler. Just add the Logger annotation created above to the Log field in the required class.
import org.slf4j.Logger;
public class Demo {
#InjectLogger
private Logger log;
public void doSomething() {
log.info("message");
log.error("Lets see how the error message looks...");
}
}

Answer 2

Why dont you use Spring AOP. AOP provides you much accessibility and features, and you can exploit its interesting features later also, when your application becomes heavy. Spring AOP