java qr code generator Pointcuts in Java

Draw QR-Code in Java Pointcuts

Table 3.3 Examples of method signatures (continued) Signature Pattern public void Account.set*(*) public void Account.*() public * Account.*() public * Account.*(..) * Account.*(..) !public * Account.*(..) Matched Methods All public methods in the Account class with a name starting with set and taking a single argument of any type. All public methods in the Account class that return void and take no arguments. All public methods in the Account class that take no arguments and return any type. All public methods in the Account class taking any number and type of arguments. All methods in the Account class. This will even match methods with private access. All methods with nonpublic access in the Account class. This will match the methods with private, default, and protected access. The static main() method of a Test class with public access. All methods in the Account class or its subclasses. This will match any new method introduced in Account s subclasses. Any read() method in the Reader class irrespective of type and number of arguments to the method. In this case, it will match read(), read(char[]), and read(char[], int, int). Any read() method in the Reader class irrespective of type and number of arguments to the method as long as the first argument type is char[]. In this case, it will match read(char[]) and read(char[], int, int), but not read(). Any method whose name starts with add and ends in Listener in the javax package or any of the direct and indirect subpackages that take one argument of type EventListener or its subtype. For example, it will match TableModel.addTableModelListener(TableModelListener). Any method that declares it can throw RemoteException.

public static void Test.main(String[] args) * Account+.*(..)

* java.io.Reader.read(..)

* java.io.Reader.read(char[],..)

* javax..*.add*Listener(EventListener+)

A constructor signature is similar to a method signature, except for two differences. First, because constructors do not have a return value, there is no return value specification required or allowed. Second, because constructors do not

have names as regular methods do, new is substituted for the method name in a signature. Let s consider a few examples of constructor signatures in table 3.4.

Table 3.4 Examples of constructor signatures Signature Pattern public Account.new() public Account.new(int) public Account.new(..) public Account+.new(..) public *Account.new(..) Matched Constructors A public constructor of the Account class taking no arguments. A public constructor of the Account class taking a single integer argument. All public constructors of the Account class taking any number and type of arguments. Any public constructor of the Account class or its subclasses. Any public constructor of classes with names ending with Account. This will match all the public constructors of the SavingsAccount and CheckingAccount classes. Any public constructors of the Account class that declare they can throw InvalidAccountNumberException.

Field signature patterns Much like the method signature, the field signature allows you to designate a member field. You can then use the field signatures to capture join points corresponding to read or write access to the specified fields. A field signature must specify the field s type, the declaring type, and the modifiers. Just as in method and constructor signatures, you can use type signature patterns to specify the types. For example, this designates a public integer field x in the Rectangle class:

Table 3.5 Examples of field signatures Signature Pattern private float Account._balance * Account.* Matched Fields Private field _balance of the Account class All fields of the Account class regardless of an access modifier, type, or name

Table 3.5 Examples of field signatures (continued) Signature Pattern !public static * banking..*.* public !final *.* Matched Fields All nonpublic static fields of banking and its direct and indirect subpackages Nonfinal public fields of any class

Now that you understand the syntax of the signatures, let s see how to put them together into pointcuts. 3.1.3 Implementing pointcuts Let s recap: Pointcuts are program constructs that capture a set of exposed join points by matching certain characteristics. Although a pointcut can specify a single join point in a system, the power of pointcuts comes from the economical way they match a set of join points. There are two ways that pointcut designators match join points in AspectJ. The first way captures join points based on the category to which they belong. Recall from the discussion in section 2.4.1 that join points can be grouped into categories that represent the kind of join points they are, such as method call join points, method execution join points, field get join points, exception handler join points, and so forth. The pointcuts that map directly to these categories or kinds of exposed join points are referred as kinded pointcuts. The second way that pointcut designators match join points is when they are used to capture join points based on matching the circumstances under which they occur, such as control flow, lexical scope, and conditional checks. These pointcuts capture join points in any category as long as they match the prescribed condition. Some of the pointcuts of this type also allow the collection of context at the captured join points. Let s take a more in-depth look at each of these types of pointcuts. Kinded pointcuts Kinded pointcuts follow a specific syntax to capture each kind of exposed join point in AspectJ. Once you understand the categories of exposed join points, as discussed in section 2.4.1, you will find that understanding kinded pointcuts is simple all you need is their syntax. Table 3.6 shows the syntax for each of the kinded pointcuts. When you understand the pointcut syntax in table 3.6 and the signature syntax as described in section 3.1.2, you will be able to write kinded pointcuts that