jxtrand

JVM	Platform	Status
OpenJDK (Temurin) Current	Linux
OpenJDK (Temurin) LTS	Linux
OpenJDK (Temurin) Current	Windows
OpenJDK (Temurin) LTS	Windows

jxtrand

Utility classes for XML string resources, and referential integrity for string resources.

Motivation

Java exposes string resources that can be localized using the ResourceBundle class. This can be backed by properties in a line-oriented text format. This text format is somewhat convenient for developers, but suffers from being line-oriented and whitespace sensitive; it becomes awkward to add significant whitespace in strings. Java properties can also be represented in an XML-based format that handles this better, but there is no built-in support for loading a ResourceBundle from an XML file. Additionally, the actual logic used by the ResourceBundle class to find property files is confusing and complex.

Lastly, Java applications using localized strings have the property names as string constants in the code. This means the code is free to drift out of sync with the property files; code can refer to properties that do not exist, and properties can become unused without much in the way of tool support to detect unused properties.

Usage

XML Files

The jxtrand package provides a convenient abstract class to load resources from XML property files. For example, an application could define the following class:

/**
 * An example where the resource is exported.
 */

public final class ExampleStrings0 extends JXTAbstractStrings
{
  /**
   * Construct an example.
   *
   * @param locale The locale
   *
   * @throws IOException On I/O errors
   */

  public ExampleStrings0(final Locale locale)
    throws IOException
  {
    super(
      locale,
      ExampleStrings0.class,
      "/com/io7m/jxtrand/examples",
      "Messages"
    );
  }
}

The class takes a Locale as an argument, and will look in the directory /com/io7m/jxtrand/examples in the module containing ExampleStrings0.class; jxtrand is module-aware.

Given:

final var lang = locale.getLanguage();
final var country = locale.getCountry();
final var ex = locale.getVariant();

The lookup procedure will look at the following files in order:

 /com/io7m/jxtrand/examples/Messages_${lang}_${country}_${ex}.xml
 /com/io7m/jxtrand/examples/Messages_${lang}_${country}.xml
 /com/io7m/jxtrand/examples/Messages_${lang}.xml
 /com/io7m/jxtrand/examples/Messages.xml

Modules

When using jxtrand in a modular context, the jxtrand will need to be able to search, reflectively, for resources inside application modules. Therefore, those modules need to be open for reflection to jxtrand. The following is typically necessary in module descriptors (assuming that resource files are kept in /com/io7m/example/internal:

module com.io7m.example
{
  opens com.io7m.example.internal
    to com.io7m.jxtrand.vanilla;

  exports com.io7m.example;
}

Resource Compiler

The jxtrand package provides a simple resource compiler that can produce enum classes from string property files (in XML or line-based formats).

Given a property file such as:

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">

<properties>
  <entry key="error.01">Error 1!</entry>
  <entry key="example2">Example 2</entry>
</properties>

The compiler can produce an enum file such as:

public enum Strings implements JXTStringConstantType
{
  ERROR_01 {
    @Override
    public String propertyName()
    {
      return "error.01";
    }
  },

  EXAMPLE2 {
    @Override
    public String propertyName()
    {
      return "example2";
    }
  }
}

These constants can be used directly with instances of the JXTStringsType class:

JXTStringsType resources;

String formatted = resources.format(ERROR_01);

Maven Plugin

The jxtrand package publishes a Maven plugin to perform resource compilation as part of a build. Use a plugin execution similar to the following:

<build>
  <plugins>
    <plugin>
      <groupId>${project.groupId}</groupId>
      <artifactId>com.io7m.jxtrand.maven_plugin</artifactId>
      <version>${project.version}</version>
      <executions>
        <execution>
          <id>generate-resources-0</id>
          <goals>
            <goal>generateSources</goal>
          </goals>
          <configuration>
            <inputFile>${project.basedir}/src/main/resources/com/io7m/jxtrand/examples/internal/Messages.xml</inputFile>
            <packageName>com.io7m.jxtrand.examples</packageName>
            <className>GeneratedStrings</className>
          </configuration>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

In the above example, the file src/main/resources/com/io7m/jxtrand/examples/internal/Messages.xml would be used to generate a Java class com.io7m.jxtrand.examples.GeneratedStrings. The class is generated as a plain Java source file and is placed in ${project.build.directory}/generated-sources/jxtrand by default (and the jxtrand directory is registered as a generated source directory automatically).