JPP: The Java Pre-Processor

Abstract

Introduction

JPP is primarily used as either a front-end for a Java compiler like javac, espresso, or guavac, or as a verification and validation tool as part of a configuration management system. We will describe both possibilities here as well as provide a number of examples of innovative alternative uses.

The default JPP configuration corresponds to the Infospheres Java Coding Standard (this document). Any questions as to the details of code standards, layout, beautification, and verification are addressed in that document. This document only focuses on the tool JPP.

All aspects of JPP are user configurable. Configuration is accomplished through the use of Java properties and command-line switches.

Briefly, JPP provides the following functionality:

• Code Beautification. JPP can process any legal Java code and reorganize it in an ordered, aesthetic manner. The rules used in the reformatting of code are user configurable. JPP is used as a code beautifier to clean up downloaded or otherwise adopted code before performing a code review. It is also used in preparation for gaining and understanding of a codebase before modifying and maintaining it. Finally, JPP can be used to process code from multiple developers/teams regularly to enforce local coding standards.
• Code Evaluation. JPP can also be used to take an existing piece of code and ``grade'' it. Such a code evaluation comes in several forms:
• Code Standard Conformance Checking. JPP is configured to a specific code standard. Code standards give rules on how code is syntactically arranged, field naming policies, feature access rules, etc. JPP can evaluate how well a piece of code conforms to its current code standard. Such an evaluation comes in the form of a short or long report which can be automatically mailed to the appropriate parties and/or logged for review.
• Code Complexity Analysis. JPP knows several standard code complexity algorithms. JPP can evaluate Java classes, interfaces, and even whole packages and provide complexity measures. These metrics can help guide a designer and developer toward more readable, understandable, and maintainable code. Metrics are also provided as short or long reports.
• Documentation Analysis. JPP can evaluate the thoroughness of code documentation. JPP knows what a ``real'' comment is and performs information theoretical complexity measures (per-feature and per-entity entropy) of comments to determine their completeness and usefulness. JPP will comment on your comments!
• Object-Oriented Design Principles. JPP understands a core set of object-oriented design principles: the Laws of Demeter, class/interface/inheritance dependency graph analysis, JavaBean patterns, and component specification to name a few. JPP can evaluate Java code and provide suggestions as to how to improve design based upon these principles.
• Class and Interface Specification. JPP's specification constructs are inspired by Meyer's Design by Contract. The primary constructs used to specify a contract for a component are method preconditions and postconditions, and class invariants. JPP can enforce and/or encourage the specification of contracts on the methods of classes and interfaces, and can test for the validity of such clauses in subtyping relationships.
• Class and Interface Testing. In addition to the aforementioned contract specifications on methods, JPP supports the specification of loop invariants and variants. All five of these constructs (the three specification clauses and the two loop clauses) can be transformed by JPP into actual embedded test harness code, inserted into a class's methods at the appropriate points. The insertion of the test code at compile time, and the enabling and disabling of test code at run-time, is completely under the control of the developer.
• Documentation Generation. JPP can also transform Java code into HTML, XML, or LaTeX for direct code documentation and reference. The resulting document is properly formatted for pretty-printing, has the appropriate embedded links for feature cross-referencing, and external language-specific links can be embedded in the code with special directives to the preprocessor.

More Information

• JPP: A Java Pre-Processor
• A local copy of the technical report is also available: (PDF | PostScript )

Related Links

• Caltech Infospheres Group
• Caltech Computer Science Department
• California Institute of Technology.

• Joseph Kiniry

• Center for Research on Parallel Computation
• Caltech Center for Research on Parallel Computation Summer Program in Computing for Undergraduate Women.
• An article about the summer program in Parallel Computing Research