This article describes the iterative sector mode using AspectJ to implement design mode. The article implements the inner arms of the AspectJ version with an example of purchasing goods.
Due to the extensive application of the iterative score, the article does not repeat the specific content of the mode, I use the specific example to explain how to use AspectJ to complete the function described. This example refers to the example of the iterative sub-mode in << Java and mode >>.
Figure 1 - Example System UML Map
Example The system first defines an abstract shopping basket class Purchase to give the behavior of the specific shopping basket and methods that need to be realized. Shopping baskets PurchaseOfcoPA and PurchaseOfcopb inherited from Purchase, which could create a forward iterative ForwardIterator and a backward iterative backawrditerator used for traversal. The system contains an abstract IteratoralASpect, which declares how the Purchase class is used to create an iteration and adapter class PURCHASEITERATOR, which implements interface java.util.uterator, and also defines an abstract PointCut Iterator Supply Lion use. Subwood ForwardITERATORASPECT and BackwardITERASPECT define the CreateETETETETERMATOR method of the respective Iterator PointCut to capture the corresponding Purchase subclass, and provides the Advice Around implementation the Createrator method to return to the corresponding category iteration. The most important thing is the internal FORWARDITERATOR and BACKWARDITERATOR in these two sub-asks that achieve the logic of forward iterations and backward iterations.
Abstract Purchase.java
Import java.util. *;
Public Abstract Class Purchase {
Private collection elements = new arraylist ();
Public void append (Object obj) {// Take home element
Elements.Add (obj);
}
Public void remove (Object obj) {// Remove element
Elements.Remove (OBJ);
}
Public Object CurrentItem (int index) {// Current element
Return ((arraylist) Elements .get (Index);
}
Public int count () {// element total
Return Elements.size ();
}
}
Specific class PurchaseOfcoPA and PurchaseOfcopb
Public Class PurchaseOfcoPA {}
Public Class PurchaseOfcopb {}
Adapter Purchaseiterator.java
Public Class PurchaseIterator {}
Abstract territory IteratoralASpect.java
Import java.util.iterator;
Public Abstract aspect iteratoralaspect {
Public iterator purchase.createiterator () {return null;}
Abstract POINTCUT ITERATOR (PURCHASE PURCHASE);
// purchaseiterator implements Iterator, used as an adapter class, supplies subscription
Declare Parents: Purchaseiterator IMPLEments ITERATOR;
INT PURCHASEITERATOR.CURRENT = 0;
Purchase purchaseiterator.purchase;
// Iterator interface method's default implementation
Public boolean purchaseiterator.hasnext () {return false;} public object purchaseiterator.next () {return null;}
Public void purchaseiterator.remove () {}
Public void purchaseiterator.Append (Object obj) {}
}
Specific aspect ForwardItemspect.java
Import java.util.iterator;
Public aspect forwardIteratoralASpect extends iteratoralaspect {
Declare Parents: PurchaseOfcopa Extends Purchase;
POINTCUT ITERATOR (Purchase Purchase): Target (Purchase)
&& call (Iterator CreateTeiterator ())
&& if (purchase instanceof purchaseofcopa; // Capture the creation method of forward iteration
Iterator Around (Purchase Purchase): Iterator (Purchase) {// creation method executes logic, and constructively iterator
Return New ForwardITERATOR (PURCHASE);
}
Private static class forwardIrtor Extends PurchaseIterator {// Before Iertone Internal Class
Public ForwardItem (Purchase Purchase) {
Super ();
this.purchase = purchase;
Current = 0; // Current cursor is the first element
}
Public Boolean Hasnext () {
Return (Current <= purchase.count () - 1);
}
Public Object next () {
IF (! Hasnext ()) {
Throw new arrayindexoutofboundsexception ("iTerator out of bounds");
}
Return Purchase.currentItem (CURRENT );
}
}
}
Specific aspect BackwardItemratoralASpect.java
Import java.util.iterator;
Public Aspect BackwardITORASPECT EXTENDS ITERATORASPECT {
DechaseOfcopb Extends Purchase;
POINTCUT ITERATOR (Purchase Purchase): Target (Purchase)
&& call (Iterator CreateTeiterator ())
&&ness (Purchase InstanceOf PurchaseOfcopb); // Capture the creation method of iterative
Iterator Around (Purchase Purchase): Iterator (Purchase) {// creation method performs logic, and the iterator
Return New BackwardITERATORTOR (PURCHASE);
}
Private static class backardItemrator Extends PurchaseIterator {// Runior iterative internal class
Public BackwardITITERATOR (Purchase Purchase) {
Super ();
this.purchase = purchase;
Current = purchase.count () - 1; // Current cursor is the last element}
Public Boolean Hasnext () {
Return (Current> = 0);
}
Public Object next () {
IF (! Hasnext ()) {
Throw new arrayindexoutofboundsexception ("iTerator out of bounds");
} else {
Return Purchase.currentItem (Current -);
}
}
}
}
Sample code DEMO.JAVA
Public class demo {
Public static void main (string [] args) throws exception {
Purchase purchasea = new purchaseofcopa ();
Purchase purchaseb = new purchaseofcopb ();
Purchasea.Append ("Dish Washer");
Purchasea.Append ("Hair Dresser");
Purchasea.append ("microwave");
System.out.Println ("Creating Forward Iterator for Purchase A);
PrintItems (Purchasea);
Purchaseb.Append ("Hair Dresser");
Purchaseb.append ("diskman");
Purchaseb.append ("DIGITAL CAMERA");
Purchaseb.Append ("PC");
Purchaseb.Append ("Dish Washer");
System.out.println ("Creating Backward Iterator for Purchase B);
PrintItems (Purchaseb);
}
Private Static Void PrintItems (Purchase Purchase) {// Format Output Element
INT INDEX = 1;
IF (IsBackforward (Purchase)) {
INDEX = Purchase.count ();
}
Iterator it = purchase.createiterator ();
While (it.hasnext ()) {
System.out.println ("Item: no" index ":" it.next (). TOSTRING ());
IF (IsBackforward (Purchase)) {
Index -;
}
Else {
INDEX ;
}
}
}
PRIVATE Static Boolean IsBackForward (Purchase Purchase) {// Is it an iteration?
IF (Purchase InstanceOf PurchaseOfcopb) {
Return True;
}
Return False;
}
}
The output is as follows
Creating Forward Iterator for Purchase A
Item no.1: Dish Washer
Item No.2: Hair Dresser
Item No.3: Microwave
Creating Backward Iterator for Purchase B
Item No.5: Dish Washer
Item No.4: PC
Item No.3: Digital Camera
Item No.2: Discmanitem No.1: Hair Dresser
At this point, I have implemented an example of using an in-arrayed child, and an interested reader can try to implement the same example of using an externalized iteration. Also because of the next month I have to participate in an important exam, the rest of this series may be slow, please also ask the readers to forgive. At the same time, because many readers don't know the AspectJ grammar, I will introduce aspectj's grammar, configuration, and use examples in another series, hoping to increase your interest in AspectJ and AOP aspects.
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