Mini Java Debugger Implementation

This is a mini-implementation of a Java Debugger using the Java Debugger Interface (JDI). For running the program, you need to execute the main entry point class JDISimpleDebugger. You will have the terminal opened and you can enter te following commands:

• step executes the next instruction. If it is une method call, the execution will enter into the method.
• step-over executes the current line.
• continue continues the execution until the next breakpoint. The granularity is the step execution.
• frame returns and prints the current frame.
• temporaries returns and prints the list of temporary variables of the current frame, under the form of pairs nom -> value.
• stack returns the execution stack of methods that was constructed to get until the reached point.
• receiver returns the receiver of the method (this).
• sender returns the object that has called the current method.
• receiver-variables return and prints the list of instance variables of the receiver under the form of a pair name -> value.
• method returns and prints the current executed method.
• arguments returns and prints the list of arguments of the current executed method under the form of a pair name -> value.
• print-var prints the value of a given variable. The name of the variable will be asked after entering the command.
• break installs a breakpoint in a specific line of a specific class. The line and the name of the file of the class will be asked after executing the command.
• breakpoints lists the breakpoints and their location in the code.
• break-once installs one breakpoint in the line number of a specific file. The values will be asked after executing the command.
• break-on-count installs one breakpoint in the line number of a specific file. This breakpoint will be only active after reaching a certain number of times. The number of times will be asked after executing the command.
• break-before-method-call configures the execution for being stopped in the beginning of the method name. The method name will be after after executing the command.

Implementation Decisions

• JavaVm is the java virtual machine. We get this class VirtualMachine from the jdi java package com.sun.jdi.virtualMachine
• JDISimpleDebugger is our main entry point.
• We used the command design pattern to implement the debugging actions that the user can use (step, step-over, receiver, etc).
• We used the null object pattern to avoid nil checking inside the commands and also in the VMHandler.
• VMHandler is an object that talks with the Java VirtualMachine to control the program execution to be debugged.
• InputInterpreter is a class that executes the corresponding user input.