This Style guide is unofficial as of yet. Please see the Code Contribution Guidelines page for our old code style recommendations, which are still currently in effect. |
If you would like to comment on this proposal, please add your thoughts to this Pull Request: https://github.com/DSpace/DSpace/pull/1895 |
K&R style braces required. Braces are also required on all blocks.
if (code) { // code } else { // code } |
Maximum length of lines is 120 characters (except for long URLs, packages or imports)
import java.util.*
). Duplicated or unused imports are also not allowed.@author
tags are optional, but should refer to an individual's name or handle (e.g. GitHub username) when includedTokens should be surrounded by whitespace, e.g. http://checkstyle.sourceforge.net/config_whitespace.html#WhitespaceAround
// This is NOT valid. Whitespace around tokens is missing String []={"one","two","three"} // This is valid. Whitespace exists around all tokens String [] = { "one", "two", "three" } |
Each line of code can only include one statement. This also means each variable declaration must be on its own line, e.g.
// This is NOT valid. Three variables are declared on one line String first = "", second = "", third = ""; // This is valid. Each statement is on its own line String first = ""; String second = ""; String third = ""; |
No empty "catch" blocks in try/catch. A "catch" block must minimally include a comment as to why the catch is empty, e.g.
try { // some code .. } catch (Exception e) { // ignore, this exception is not important } |
All "switch" statements must include a "defaut" clause. Also, each clause in a switch must include a "break", "return", "throw" or "continue" (no fall throughs allowed), e.g.
// This is NOT valid. Switch doesn't include a "default" and is missing a "break" in first "case" switch (myVal) { case "one": // do something case "two": // do something else break; } // This is valid. Switch has all necessary breaks and includes a "default" clause switch (myVal) { case "one": // do something break; case "two": // do something else break; default: // do nothing break; } |
Any "utility" classes (a utility class is one that just includes static methods or variables) should have private constructors, e.g.
// This is an example class of static constants public class Constants { public static final String DEFAULT_ENCODING = "UTF-8"; public static final String ANOTHER_CONSTANT = "Some value"; // As this is a utility class, it MUST have a private, empty constructor private Constants() { } } |
Each source file must contain the required DSpace license header, e.g.
/** * The contents of this file are subject to the license and copyright * detailed in the LICENSE and NOTICE files at the root of the source * tree and available online at * * http://www.dspace.org/license/ */ |
Per the Code Contribution Guidelines page (see "Coding Conventions" section), our existing style guide is listed as follows:
Your code needs to follow the Sun Java code conventions with the following minor modifications:
- Curly braces must be on new lines.
- Source files must have a copy of the copyright Duraspace notice and BSD license at the top (see Licensing of Contributions below). Also take a look at Copyright and Licensing.
- You must use 4-space tabulation.
- 'else' should be on a new line. 'else if' stays on one line.
- Users of the Eclipse IDE can have eclipse do the formatting automatically using this profile: - Dspace-eclipse-format.xml. See the Eclipse section below for details of how to apply this profile.
Your code should be well commented with Javadoc (including package and class overviews). All code contributions must come with Documentation. At a bare minimum, this should include Technical Documentation covering all configuration options and/or setup. See Documentation Contributions below for more details.
These existing style guidelines are based heavily on the Sun coding conventions (circa 1999) which are no longer maintained, but still available at http://www.oracle.com/technetwork/java/javase/documentation/codeconvtoc-136057.html
Because the Sun Java style guide is no longer maintained, it will not be keeping up with current Java style best practices, features, etc. We should consider whether we continue to base our style off this outdated guide, use a more modern guide, or develop our own guide.
The Google Java Style Guide is at https://google.github.io/styleguide/javaguide.html
Some of the primary differences of this style include:
The Fedora project has its own style guide at https://wiki.duraspace.org/display/FF/Code+Style+Guide
Some of the primary differences of this style include:
While not yet implemented, we likely would want to implement some verification of code style guidelines via Checkstyle. Checkstyle is widely used in the Java world, and supports both Google and Sun Java conventions, as well as custom configurations.
Which git branches would we want to enable Checkstyle on?
master
branch, and perhaps just specific modules (e.g. "dspace-spring-rest") on the master
branch.master
branch only may complicate cherry-picking of code changes from other branches (as line numbers, spacing, etc may change when the code is updated to use the latest DSpace Style Guide)Most major IDEs include plugins that support Checkstyle configurations. The plugin usually let you import an existing "checkstyle.xml" configuration to configure your IDE to use and/or validate against that style. (Please note: we have not tested all these plugins as of yet, so mileage may vary until we test/verify the plugin is usable)
checkstyle.xml
+
in the table). Select our checkstyle.xml
checkstyle.xml
*.java, *.xml
" (As we'll only bulk reformat Java and XML files)Finally, run Checkstyle against the module. There likely will still be a few failures to fix manually.
# mvn install (Only necessary if checkstyle:check below complains about missing SNAPSHOT dependencies) mvn -U checkstyle:check |
Also double check license headers are still accurate. Sometimes these get "munged" during bulk reformat (as IDEA occasionally tries to merge nearby comments into one larger comment)
mvn license:check |