Class Viewer for Java Class Viewer Design

Lightweight, quick reference tool for Java developers.

Brought to you by: jstevh

ClassViewerDesign

Class Viewer Overall Design

Component: Class Viewer (public-API quick reference)
Status: ✅ Released 6.0.0 (maintenance / packaging refresh; no new features)
Last Updated: August 26, 2026
Author: jstevh

Class Viewer is a lightweight, stateless Java desktop tool for looking at the public surface of a class: methods, constructors, fields, superclass, and interfaces. It is not a decompiler and not an IDE. It uses reflection, a small Swing UI, and an editable XML config to jump from a listed method to JavaDocs in a browser, or to local source in a text editor.

On SourceForge since February 2004. Current packaged entry point: com.jstevh.viewer.ClassViewer.

Core Design Principles

Public surface only. The tool shows what java.lang.reflect exposes as public members. It does not parse bytecode, reconstruct private implementation, or rewrite source.
Stateless runtime. No session store, no project file, no installer. Configuration lives in ClassViewerConfig.xml beside the working directory. Restart to pick up config edits.
Config-driven documentation routing. Package names map to documentation groups (web JavaDocs or local files). Browser and editor paths are user-editable XML, not compiled constants.
Classpath is the world. The JVM classpath is the set of classes the tool can load. Run the executable JAR for a quick look; unpack and run from the command line when you need your own classes and jars on the classpath.
Small, readable modules. Eight Java source files compile to 26 class files. Two packages: com.jstevh.viewer and com.jstevh.tools.
External tools, not embedded ones. JavaDocs open in the configured browser. Local source opens in the configured editor. Class Viewer stays a viewer.

High-Level Architecture

User / CLI argument
        │
        ▼
┌───────────────────────────────────────┐
│  ClassViewer                          │
│  Swing UI + main + launch helpers     │
│  VERSION = 6.0.0                      │
└───────────────┬───────────────────────┘
                │
        ┌───────┴────────┐
        ▼                ▼
┌───────────────┐  ┌─────────────────────┐
│  DirManager   │  │  ClassInfo          │
│  + SAXDirParser│  │  java.lang.reflect  │
│  reads XML    │  │  load class         │
└───────┬───────┘  │  list members       │
        │          │  search methods     │
        ▼          └──────────┬──────────┘
ClassViewerConfig.xml         │
  Local: browser, editor      ▼
  Documentation groups   StringTools / StringList
        │                method-name search
        ▼
 Browser (JavaDocs URL)   Editor (local source)
 Runtime.exec launch      optional line-number arg

Key Design Components

Class	Package	Role
`ClassViewer`	`com.jstevh.viewer`	Main window, menus, font-size range, browser/editor launch, `main`
`ClassInfo`	`com.jstevh.viewer`	Loads a class by name; lists public fields, methods, constructors, interfaces, superclass; method search
`DirManager`	`com.jstevh.viewer`	Owns config load state; exposes package list, browser, editor, font preference
`SAXDirParser`	`com.jstevh.viewer`	SAX parse of `ClassViewerConfig.xml` (`DefaultHandler`)
`MethodData`	`com.jstevh.viewer`	Small interface: package, class, method name for a found method
`StringList`	`com.jstevh.tools`	Minimal string collection used by config and search
`StringTools`	`com.jstevh.tools`	`searchStrings` / `removeStrings` helpers for method search and signature cleanup

Runtime Flow (Current Implementation)

Launch via java -jar ClassViewer-6.0.0.jar (or ClassViewer.bat on Windows), optionally with a class name argument such as java.lang.String.
DirManager + SAXDirParser read ClassViewerConfig.xml from the directory the process was started in. Missing XML is a known failure mode: the app will not resolve packages or tools without that file beside the launch directory.
User types or pastes a fully qualified class name (or uses the CLI argument). ClassInfo calls Class.forName / reflection against the current classpath.
UI shows:
class package and name
superclass
implemented interfaces
public constructors
public fields
public methods
Free-text search filters public method names through ClassInfo.srchMethods + StringTools.
Selecting documentation:
package is looked up in the config Documentation/Group/Names map
if the group is web-backed, callBrowser opens the configured browser at the JavaDocs base URL
if the group is local (<Local>Yes</Local>) and an editor is configured, the local file is opened
if <acceptsLineNumber>Yes</acceptsLineNumber>, the editor is invoked with the configured line-number parameter (gedit is the documented example)

Configuration Model

ClassViewerConfig.xml is the only user-facing configuration surface. It is ordinary XML and is meant to be edited in a text editor.

<Base>
  <Local>            browser, editor, line-number flag, font preference
  <Documentation>
    <Group>          description, owner, web-or-local location, package names

Local block

BrowserLoc — executable used for JavaDocs (Windows 6.0.0 package: explorer.exe)
Editor — executable used for local source (Windows 6.0.0 package: notepad.exe)
acceptsLineNumber / parameter — whether the editor can be pointed at a line
LargerFonts — raises the default font and the allowed increase/decrease range

Documentation groups

Each group has a JavaDocs base URL or a local-file flag, plus a list of package prefixes.
Packages beginning with java historically fall back to a default docs location when not listed.
The 6.0.0 Windows package ships three groups: Java SDK 8.0 (Oracle web docs), Java Enterprise / Swing (Oracle web docs), and Class Viewer itself (com.jstevh.viewer, com.jstevh.tools) as local.

The JAR is platform-independent. Windows vs Linux packages differ in this XML and in the launcher script, not in the viewer classes.

Launch and Classpath Model

Two supported ways to run, unchanged in spirit since the 5.x line:

Mode	How	Why
Executable JAR	`java -jar ClassViewer-6.0.0.jar` or `ClassViewer.bat`	Fast start; good for JDK classes already on the JRE
Unpacked	`jar -xf ClassViewer-6.0.0.jar` then run `com.jstevh.viewer.ClassViewer` with a real classpath	Required to inspect your classes and third-party jars

No installer is used or included. The app does not write back to the XML at runtime.

UI and Interaction Surface

Kept small on purpose:

Class-name entry and load
Results pane for public members
Method search
Font size within a fixed band (default 12→10..14, or larger-font mode 13→11..17)
Right-click copy from the results window to the system clipboard
Help links consolidated under the Help menu (Weblinks menu removed in 5.1.0 and not restored)
Optional CLI class name so the first screen can open already populated

Font limits live as ClassViewer.MAX_FONT_SIZE / MIN_FONT_SIZE, seeded from the XML LargerFonts flag.

Design Guarantees

Feature	Status	How it is implemented	Benefit
Public-only view	✅ Done	`ClassInfo` via `java.lang.reflect`	Fast, honest API picture; no decompiler drift
Method search	✅ Done	`srchMethods` + `StringTools.searchStrings`	Quick filter without leaving the tool
Superclass + interfaces	✅ Done	`ClassInfo.getSuperClassName` / `printInterfaces`	Immediate type-context
JavaDocs jump	✅ Done	Package→group map + `callBrowser`	Opens docs at the selected method when the URL scheme allows
Local source jump	✅ Done	Local group + editor + optional line number	Same gesture for your own code
Editable config	✅ Done	`ClassViewerConfig.xml` + `SAXDirParser`	No rebuild to change browser, editor, or docs roots
Stateless	✅ Done	No session files; XML is input only	Predictable; safe to copy the folder
Small artifact	✅ Done	~44 KB JAR; eight source files	Easy to audit and ship
Java 21 package verify	✅ Done (6.0.0)	OpenJDK 21 compile + executable JAR	Current-runtime confidence
Java 8 runtime claim	☐ Confirm separately	Source is still Java-era; 6.0.0 did not re-certify Java 8	Avoid a false compatibility promise

What 6.0.0 Changed (and Did Not)

6.0.0 is a maintenance and packaging release. Functional behavior is the existing Class Viewer tool, not a new product.

Verified in the 6.0.0 package:

Eight Java source files compile on OpenJDK 21
Build produces 26 class files and a runnable executable JAR
Main-Class: com.jstevh.viewer.ClassViewer
ClassViewerConfig.xml is well-formed and shipped beside the JAR
Windows zip includes launcher, licenses (COPYING, COPYING.LESSER), NOTICE, SHA256SUMS, README.md, RELEASE-NOTES.md

Intentionally out of scope for 6.0.0:

New features
Cleaning raw reflection types
Replacing deprecated AccessControlException and Runtime.exec(String)
Constructor this escape warning
Claiming a freshly tested Java 8 runtime

Those warnings still compile and package. They are recorded so a later cleanup pass can be honest about cost.

Package Layout (6.0.0)

com.jstevh.viewer
    ClassViewer.java      UI + process launch
    ClassInfo.java        reflection model
    DirManager.java       config façade
    SAXDirParser.java     XML parse
    MethodData.java       found-method handle

com.jstevh.tools
    StringList.java       small list
    StringTools.java      search / strip helpers

Distribution (Windows 6.0.0 folder):

ClassViewer-6.0.0.jar
ClassViewerConfig.xml
ClassViewer.bat
README.md, RELEASE-NOTES.md, NOTICE
COPYING, COPYING.LESSER
SHA256SUMS

Progress & Next Steps (as of August 26, 2026)

✅ 6.0.0 packaged and published on SourceForge
✅ Java 21 compile + executable JAR verified
✅ Windows launcher + XML + license bundle
✅ Linux package also published
☐ Confirm Java 8 runtime separately before restating a legacy-runtime guarantee
☐ Optional later cleanup of recorded javac -Xlint warnings (not a feature release)
☐ Create [[Configuration Design]] wiki page (XML schema and package-mapping rules)
☐ Create [[Launch and Classpath]] wiki page (jar vs unpacked, common failure modes)

[[Home]]
[[Configuration Design]] (planned next)

This page is part of the Class Viewer design documentation. Written against the 6.0.0 SourceForge package (trunk assembled 2026-08-26). Project: https://sourceforge.net/projects/classviewer/