Skip to main content

Spring - AOP Terms 


• Aspect: a modularization of a concern that cuts across multiple classes.In Spring AOP, aspects are implemented using regular classes (the schema-based approach) or regular classes annotated with the
@Aspect annotation (the @AspectJ style).
• Join point: a point during the execution of a program, such as the execution of a method or the handling of an exception. In Spring AOP, a join point always represents a method execution.
• Advice: action taken by an aspect at a particular join point. Different types of advice include "around," "before" and "after" advice. (Advice types are discussed below.) Many AOP frameworks, including Spring, model an advice as an interceptor, maintaining a chain of interceptors around the join point.
• Pointcut: a predicate that matches join points. Advice is associated with a pointcut expression and runs at any join point matched by the pointcut (for example, the execution of a method with a certain name).
The concept of join points as matched by pointcut expressions is central to AOP, and Spring uses the AspectJ pointcut expression language by default.
• Introduction: declaring additional methods or fields on behalf of a type. Spring AOP allows you to introduce new interfaces (and a corresponding implementation) to any advised object. For example, you could use an introduction to make a bean implement an IsModified interface, to simplify caching. (An introduction is known as an inter-type declaration in the AspectJ community.)
• Target object: object being advised by one or more aspects. Also referred to as the advised object.Since Spring AOP is implemented using runtime proxies, this object will always be a proxied object.
• AOP proxy: an object created by the AOP framework in order to implement the aspect contracts(advise method executions and so on). In the Spring Framework, an AOP proxy will be a JDK dynamic proxy or a CGLIB proxy.
• Weaving: linking aspects with other application types or objects to create an advised object. This can be done at compile time (using the AspectJ compiler, for example), load time, or at runtime. Spring AOP, like other pure Java AOP frameworks, performs weaving at runtime.
Types of advice:
• Before advice: Advice that executes before a join point, but which does not have the ability to prevent execution flow proceeding to the join point (unless it throws an exception).
• After returning advice: Advice to be executed after a join point completes normally: for example, if a method returns without throwing an exception.
• After throwing advice: Advice to be executed if a method exits by throwing an exception. 
• After (finally) advice: Advice to be executed regardless of the means by which a join point exits (normal or exceptional return).
• Around advice: Advice that surrounds a join point such as a method invocation. This is the most powerful kind of advice. Around advice can perform custom behavior before and after the method Spring Framework

Comments

Post a Comment

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
Post a Comment
Read more

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        
1 comment
Read more

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"/>
4 comments
Read more