oosc - jmsassert. design by contract a powerful technique for writing reliable software. specifying...

OOSC - JMSAssertOOSC - JMSAssert

Design By ContractDesign By Contract A powerful technique for writing reliable

software. Specifying the software purpose with the

implementation. Key elements:

Invariant Preconditions Postconditions

Design By ContractDesign By Contract Precondition – The constraints under

which the routine will function properly. Postconditions – The state of the class after

the routine execution The Contract: If you call routine R() with

the preconditions satisfied, R() will return satisfying the postconditions.

Invariant – Always holds

When are condition checked?When are condition checked?

Event InvariantPre-

conditionPost-

conditionInstance Method Y Y -Constructor N Y -Private Method N Y -Static Method N Y -Instance Method Y - YConstructor Y - YPrivate Method N - YStatic Method N - Y

Method Entry

Method Exit

JMS Syntax - InvariantJMS Syntax - Invariant Invariant - @inv May access all class members or its

direct/indirect bases, including private members

May appear in any JavaDoc comment Preferable in the class comment

JMS Syntax - PreconditionsJMS Syntax - Preconditions Precondition - @pre JavaDoc preceding the respective method May reference class members and

arguments Multiple @pre markers are conjugated

(AND)

JMS Syntax - PostconditionsJMS Syntax - Postconditions Postconditions - @post JavaDoc preceding the respective method May use $prev(expression) to access the

value at the method entry. May use $ret to denote method’s return

value Multiple @post markers are conjugated

(AND)

ExampleExample/** * @pre !isEmpty() * @post (top == $prev(top- 1)) * @post $ret == elems[top] * @post !isFull*/

public synchronized Object pop() {return elems[--top];

}

Precondition

Postconditions

JMS Syntax - GeneralJMS Syntax - General Order has no meaning @macro – for complicated conditions Recursion – as expected, on every call Inner classes can access outer classes’

members Anonymous classes – specify invariant in

one of its methods

JMSAssert InstallationJMSAssert Installation Run the jmssetup-1.02.exe installation file The following lines are added to the path:REM Next two lines are added by JMSAssertSET CLASSPATH=%CLASSPATH%;C:\PROGRA~1\JMSASS~1.0\bin\mmsclasses.jar;SET PATH=%PATH%;C:\PROGRA~1\JMSASS~1.0\bin; Copy the “classic” directory from

“..\jdk1.3.1\jre\bin\” to the directory:“C:\Program Files\JavaSoft\JRE\1.3\bin\”

Setup Setup (cont.)(cont.)

Your JavaSoft directory should look like:

If you use jdk 1.2.2, you will have a 1.2 directory

JMSAssert – how does it workJMSAssert – how does it work Annotate source code with assertions Compile your code using javac (as usual) Preprocess the code using jmsassert: creates

contract files (*.jms) and a Startup.jms file. *.jms files contain java code for the assertions. Execute using: jmsjava Startup <filename>to check assertions.

jmsjava makes sure method assertions are called before/after the method invocation.

JMS ExecutionJMS Execution “jmsassert” – generates help text “jmsassert –s <filename.java>” – generate

assertions for a class file “jmsassert –r –s .” – generate assertions for

all class files in the directory and sub-dirs. (use for packages)

“javac <filename.java>” – compile “jmsjava Startup <main>” - execute and check

assertions

Annotate source with assertions

Preprocess to generate assertion

filesJmsassert –s <file.java>

Compile Java file

javac <file.java<

Execute using jmsjava

MyStack.java

Startup.jms

default_MyStack.jmsdefault_MyStack_StackEnum.jms

MyStack.classMyStack$StackEnum.classMyStack$StackEnum.classJmsjava Startup <file.java> StackTest.class

Stack Demo Stack Demo filesfiles

Execution Execution processprocess

NotesNotes Execute these steps form the command line! Make sure your CLASSPATH environment

variable contains the current directory.Add “CLASSPATH=%CLASSPATH%;.;” to autoexec.bat.