Skip to main content

Some Concepts about Spring Framework

Advice:
Advice specifies what to do at a joint point. In the case of Spring, this is the additional behavior that Spring will inject around a method invocation. It is most often defined in a method interceptor, which will be invoked as part of  an interceptor chain wrapping the method invocation.

Advice Type:
Before Advice, as its name implies, executes before the joint point
After Returning Advice: is inoked when a method returns successfully, without throw an exception
Throws Advice:

The following advice is invoked if a ServletException or a RemoteException is thrown. This class implements an afterThrowing() method taking all four arguments, so it has access to the invoked method, method arguments, and target object:

public static class ServletThrowsAdviceWithArguments implements ThrowsAdvice {
 
    public void afterThrowing(Method m, Object[] args, Object target,
ServletException ex) {
        // Do something with all arguments
    }
 
    public void afterThrowing(RemoteException ex) throws Throwable {
        // Do something with remote exception
    }
}


Pointcuts:
Pointcuts identify where advice should apply.

Spring Pointcut Concepts:
Spring pointcuts are essentially ways of identifying method invocations that fit a certain criteria.

Advisors: In order to pull pointcuts and advice together, we need an object that contains both: that is, containing the behavior that should be added(advice) and where that behavior should apply(pointcut). Spring introduces the concept of an Advisor. an object that includes both advice and a pointcut speciying where that advice should apply. Unlike advice and pointcut, an advisor is not an established AOP concept, but a Spring-specific term.

The purpose of an Advisor is to allow both advice and pointcuts to be reusable independently.

Introduction: means an advised object implement additional interfaces, which are not implemented by the target object.

Comments

Popular posts from this blog

Quicksort implementation by using Java

 source: http://www.algolist.net/Algorithms/Sorting/Quicksort. The divide-and-conquer strategy is used in quicksort. Below the recursion step is described: 1st: Choose a pivot value. We take the value of the middle element as pivot value, but it can be any value(e.g. some people would like to pick the first element and do the exchange in the end) 2nd: Partition. Rearrange elements in such a way, that all elements which are lesser than the pivot go to the left part of the array and all elements greater than the pivot, go to the right part of the array. Values equal to the pivot can stay in any part of the array. Apply quicksort algorithm recursively to the left and the right parts - the previous pivot element excluded! Partition algorithm in detail: There are two indices i and j and at the very beginning of the partition algorithm i points to the first element in the array and j points to the last one. Then algorithm moves i forward, until an element with value greater or equal

Live - solving the jasper report out of memory and high cpu usage problems

I still can not find the solution. So I summary all the things and tell my boss about it. If any one knows the solution, please let me know. Symptom: 1.        The JVM became Out of memory when creating big consumption report 2.        Those JRTemplateElement-instances is still there occupied even if I logged out the system Reason:         1. There is a large number of JRTemplateElement-instances cached in the memory 2.     The clearobjects() method in ReportThread class has not been triggered when logging out Action I tried:      About the Virtualizer: 1.     Replacing the JRSwapFileVirtualizer with JRFileVirtualizer 2.     Not use any FileVirtualizer for cache the report in the hard disk Result: The japserreport still creating the a large number of JRTemplateElement-instances in the memory        About the work around below,      I tried: item 3(in below work around list) – result: it helps to reduce  the size of the JRTemplateElement Object        

Stretch a row if data overflows in jasper reports

It is very common that some columns of the report need to stretch to show all the content in that column. But  if you just specify the property " stretch with overflow' to that column(we called text field in jasper report world) , it will just stretch that column and won't change other columns, so the row could be ridiculous. Haven't find the solution from internet yet. So I just review the properties in iReport one by one and find two useful properties(the bold  highlighted in example below) which resolve the problems.   example: <band height="20" splitType="Stretch" > <textField isStretchWithOverflow="true" pattern="" isBlankWhenNull="true"> <reportElement stretchType="RelativeToTallestObject" mode="Opaque" x="192" y="0" width="183" height="20"/> <box leftPadding="2"> <pen lineWidth="0.25"/>