Retrotranslator

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Contents

  1. What is Retrotranslator?
  2. What Java 5.0 features are supported?
  3. How to use Retrotranslator from the command line?
  4. How to use Retrotranslator from Apache Ant or Maven?
  5. How to use Retrotranslator from IntelliJ IDEA?
  6. How to produce a jar file compatible with Java 1.4?
  7. How to use Just-in-Time Retrotranslator?
  8. What API is supported on Java 1.4 and Java 1.3?
  9. How to write an extension?
  10. What are the limitations?
  11. Alternative tools
  12. Contact
  13. License

What is Retrotranslator?

Retrotranslator is a tool that makes Java applications compatible with Java 1.4, Java 1.3 and other environments. It supports all Java 5.0 language features and a significant part of the Java 5.0 API on both J2SE 1.4 and J2SE 1.3. In other Java environments only the Java 5.0 features that don't depend on the new API are supported. Retrotranslator employs the ASM bytecode manipulation framework to transform compiled Java classes and the backport of the Java 5.0 concurrency utilities to emulate the Java 5.0 API.

What Java 5.0 features are supported?

How to use Retrotranslator from the command line?

  1. Download and unzip the binary distribution file Retrotranslator-n.n.n-bin.zip, where n.n.n is the latest Retrotranslator release number.
  2. Compile your classes with Java 5.0 or Java 6 and put them into some directory, e.g. myclasses.
  3. Go to the unzipped directory and execute:
    java -jar retrotranslator-transformer-n.n.n.jar -srcdir myclasses
    Use appropriate options to verify the result and for troubleshooting, e.g. -verify, -classpath, -advanced, and -smart.
  4. Put retrotranslator-runtime-n.n.n.jar and backport-util-concurrent-n.n.jar into the classpath of your application if you use the Java 5.0 API.
  5. Run or debug the application as usual on Java 1.4.

The command line syntax:
java -jar retrotranslator-transformer-n.n.n.jar <options>
or
java -cp retrotranslator-transformer-n.n.n.jar net.sf.retrotranslator.transformer.Retrotranslator <options>

Option Description Default
-srcdir <path> The directory with the files to process (can be specified several times). -
-srcjar <file> The jar file with the files to process (can be specified several times). -
-destdir <path> The directory to place processed files. The source.
-destjar <file> The jar file to place processed files. The source.
-srcmask <mask> The wildcard pattern specifying the files to transform rather than copy (classes or UTF-8 text files), e.g. *.class;?*.tld. *.class
-target <version> The version of the JVM where the translated application should be able to run (1.1, 1.2, 1.3, 1.4, or 1.5). The Java 5.0 API is supported only for the 1.4 and 1.3 targets, but user-defined backport classes can be used for other targets as well. 1.4
-classpath <path> The dependencies of the translated classes including backport packages and jar files from the target JVM. For the 1.4 target the following files should be specified among others: rt.jar, jce.jar, and jsse.jar from Sun JRE 1.4; retrotranslator-runtime-n.n.n.jar and backport-util-concurrent-n.n.jar. For the 1.3 target the files are: rt.jar from Sun JRE 1.3, retrotranslator-runtime13-n.n.n.jar and backport-util-concurrent-java12-n.n.jar. This option can be omitted if the current Java environment matches the target one. The current classpath.
-verify Asks the translator to examine translated bytecode for references to classes, methods, or fields that cannot be found in the classpath. Every use of Java 5.0 API will result in a warning message if the classpath contains jar files from JRE 1.4. false
-support <features> Enables advanced features. The names specified should be separated with semicolons, e.g. ThreadLocal.remove;BigDecimal.setScale. -
-advanced Enables all advanced features at once, but it's recommended to enable only required features in order to avoid compatibility issues. false
-smart Makes all backport classes inheritable provided that the classpath correctly reflects the target environment. For example, the backport of the Writer.append(String) method can be used to translate the following expression: new FileWriter("file.tmp").append("Hello"). false
-syncvolatile Makes access to volatile fields of Java 5.0 classes compliant with Java 5.0 memory model at the cost of decreased performance. Highly recommended to use. false
-syncfinal Makes access to final instance fields of Java 5.0 classes compliant with Java 5.0 memory model at the cost of decreased performance. Not recommended to use. false
-backport <names> The backport names separated with semicolons, e.g. com.myco.all;java.util:com.myco.ju;javax.net.SocketFactory:com.myco.jsse.Factory. The corresponding backport classes must be present in the classpath. -
-embed <package> The unique package name for a partial copy of retrotranslator-runtime-n.n.n.jar and backport-util-concurrent-n.n.jar to be put along with translated classes. This makes the translated application independent of other versions of Retrotranslator present in the classpath. -
-lazy Asks the translator to transform and verify only the classes compiled with a target greater than the current one. false
-stripsign Whether to remove signature (generics) information. false
-stripannot Whether to remove annotations and related attributes. false
-verbose Asks the translator for verbose output. false
-retainapi Asks the translator to modify classes for JVM compatibility but keep use of API unless overriden with the backport option. Any references introduced by a compiler remain unchanged, like the use of java.lang.StringBuilder for string concatenation or the implicit valueOf method calls for autoboxing. false
-keepclasslit Prevents replacement of certain types like java.lang.Iterable or java.util.Queue with their base types in class literals. false
-retainflags Whether to keep Java 5.0 specific access modifiers. false
-uptodatecheck Asks the translator to skip processing of files if the destination files are newer. false
-reflection <mode> Setting this option to safe makes the translator include additional metadata into classes, so reflection works even if the classes are unavailable as resources. normal

How to use Retrotranslator from Apache Ant or Maven?

The distribution contains an Apache Ant task net.sf.retrotranslator.transformer.RetrotranslatorTask. Every command line option can be set using the corresponding attribute. In addition the source files can be specified with nested fileset, jarfileset, and dirset elements and the classpath can be set with nested classpath elements or the classpathref attribute. The source directories specified with srcdir, dirset, and the dir attribute of fileset should contain the root package of the classes. In case of warnings the build fails unless the value of the failonwarning attribute is set to false. The following script can be used to build one jar compatible with Java 1.4 and another one compatible with Java 1.3.

    <taskdef name="retrotranslator" classname="net.sf.retrotranslator.transformer.RetrotranslatorTask">
        <classpath>
            <fileset dir="../Retrotranslator-n.n.n-bin">
                <include name="retrotranslator-transformer-n.n.n.jar" />
                <include name="retrotranslator-runtime-n.n.n.jar" />
                <include name="backport-util-concurrent-n.n.jar" />
            </fileset>
        </classpath>
    </taskdef>
    
    <retrotranslator target="1.4" destjar="build/application14.jar"
                     smart="true" verify="true" failonwarning="false">
        <fileset dir="build/classes" includes="**/*.class" />
        <jarfileset dir="build/lib" includes="**/*.jar" />
        <classpath>
            <fileset dir="../j2sdk1.4.2_17/jre/lib" includes="**/*.jar"/>
            <fileset dir="../Retrotranslator-n.n.n-bin">
                <include name="retrotranslator-runtime-n.n.n.jar" />
                <include name="backport-util-concurrent-n.n.jar" />
            </fileset>
            <fileset dir="lib" includes="**/*.jar"/>
        </classpath>
    </retrotranslator>

    <retrotranslator target="1.3" destjar="build/application13.jar"
                     smart="true" verify="true" failonwarning="false">
        <fileset dir="build/classes" includes="**/*.class" />
        <jarfileset dir="build/lib" includes="**/*.jar" />
        <classpath>
            <fileset dir="../jdk1.3.1_20/jre/lib" includes="**/*.jar"/>
            <fileset dir="../Retrotranslator-n.n.n-bin">
                <include name="retrotranslator-runtime13-n.n.n.jar" />
                <include name="backport-util-concurrent-java12-n.n.jar" />
            </fileset>
            <fileset dir="lib" includes="**/*.jar"/>
        </classpath>
    </retrotranslator>

Maven users can use the Retrotranslator plugin from the Mojo Project.

How to use Retrotranslator from IntelliJ IDEA?

There is a plugin to automatically translate and verify classes compiled by IntelliJ IDEA, so you can develop in Java 5.0 but run and debug on Java 1.4.

How to produce a jar file compatible with Java 1.4?

If you have a myapplication5.jar file built with Java 5.0 you can use the following command to produce myapplication4.jar. The jar file will be compatible with Java 1.4 and independent of Retrotranslator because backport classes are added to the translated application with a different package name.

java -jar retrotranslator-transformer-n.n.n.jar -srcjar myapplication5.jar -destjar myapplication4.jar -embed com.mycompany.internal

Also it is recommended to specify the classpath, verify, and smart options. In case of verification failure try the support option.

How to use Just-in-Time Retrotranslator?

In order to run a Java 5.0 application on Java 1.4 start it with JIT Retrotranslator using one of the following commands:

The options include support, advanced, smart, backport, syncvolatile, syncfinal, and keepclasslit. When running on J2SE 5.0 JIT Retrotranslator simply calls the application, but on J2SE 1.4 it also translates classes compiled for Java 5.0 or later. However this capability depends on the current JVM and the application itself, so under certain conditions JIT Retrotranslator may be unable to translate either a jar file or classes from the classpath or both.

What API is supported on Java 1.4 and Java 1.3?

An asterisk designates all API members introduced in Java 5.0. Most classes and methods added in Java 1.4 and in Java 6.0 cannot be used on earlier VMs.

Package Class Members Compatibility notes
java.io Closeable2 * (all members introduced in Java 5.0)  
Flushable2 *  
PrintStream * (11 new methods and constructors)
PrintStream(File, String)5,
PrintStream(String, String)5
 
PrintWriter * (11 new methods and constructors) The PrintWriter.format and PrintWriter.printf methods always flush the output buffer.
Reader5 * (1 new method)  
Writer * (3 new methods)  
java.lang Appendable2 *  
Boolean * (2 new methods)
toString(boolean)6,
valueOf(boolean)6
 
Byte * (1 new method)  
Character * (44 new methods)
getDirectionality(int)5,
isMirrored(int)5,
toString(char)6
New members of Character.UnicodeBlock are not supported. All supplementary code points are considered as unassigned.
CharSequence6 *  
Class * (21 new methods) Enable feature "Class.forName" to use backported classes as a fallback when calling this method3.
Enable features "Class.getMethod" and "Class.getDeclaredMethod" to use most of backported static methods as a fallback when calling these methods and for more uniform support of generics and covariant return types on different platforms3.
Deprecated *  
Double valueOf(double)  
Enum *  
Float valueOf(float)  
IllegalArgumentException * (2 new constructors)  
IllegalStateException * (2 new constructors)  
Integer valueOf(int),
signum(int)
 
Iterable2 *  
Long valueOf(long),
signum(long)
 
Math cbrt(double), cosh(double),
expm1(double), log10(double),
log1p(double), signum(double),
signum(float), sinh(double),
tanh(double)
The quality of computation may be insufficient for applications of certain types.
Package * (4 new methods) Enable feature "Retrotranslator.fixHyphen" to change the name of package-info classes to package$info3.
Readable2,5 *  
Short * (2 new methods)  
StackTraceElement6 * (1 new constructor)  
String * (10 new methods and constructors)
isEmpty()4
Enable features "String.matches", "String.replaceAll", "String.replaceFirst" and "String.split" to support Java 5.0 features in regular expressions when calling these methods on Java 1.43 (they are unavailable on Java 1.3).
StringBuffer * (11 new methods and constructors) append(StringBuffer)6 Enable feature "StringBuffer.trimToSize" to use an empty implementation of the StringBuffer.trimToSize() method3.
StringBuilder * StringBuilder is being replaced with StringBuffer.
SuppressWarnings *  
System nanoTime()1,
clearProperty(String)
The System.nanoTime() method precision may vary on different platforms.
Enable feature "System.getProperty" to identify the current JVM as compatible with Java 5.0 when calling this method at runtime3.
Thread * (8 new methods) The Thread.getId() method does not reflect the order in which threads have been created.
The Thread.getStackTrace() and Thread.getAllStackTraces() methods return non-empty stack trace only for the current thread.
Enable feature "Thread.getState" to support this method, but it will detect only NEW, RUNNABLE and TERMINATED states.3
Enable features "Thread.setUncaughtExceptionHandler" and "Thread.setDefaultUncaughtExceptionHandler" to support exception handlers for threads created by translated code (in contrast to Java 5.0 the default UncaughtExceptionHandler takes precedence over ThreadGroup)3.
Thread.State *  
Thread.UncaughtExceptionHandler2 *  
ThreadLocal * (1 new method) Enable feature "ThreadLocal.remove" to use alternative ThreadLocal and InheritableThreadLocal implementations with method remove()3.
TypeNotPresentException *  
Throwable Throwable(String, Throwable)6,
Throwable(String, Throwable)6,
getCause()6,
getStackTrace()6,
initCause(Throwable)6
The additional constructors and methods are available for all Java 1.3 exception classes if the smart option has been used.
UnsupportedOperationException * (2 new constructors)  
java.lang.annotation * (all classes) *  
java.lang.instrument * * Bytecode instrumentation is not implemented.
java.lang.management ManagementFactory getPlatformMBeanServer() The ManagementFactory.getPlatformMBeanServer() method simply returns the first registered MBeanServer or creates it when no one exists. Requires an implementation of JMX 1.2.
java.lang.ref SoftReference * Enable feature "SoftReference.NullReferenceQueue" to support null for the second parameter of SoftReference(Object,ReferenceQueue) on all platforms3.
WeakReference * Enable feature "WeakReference.NullReferenceQueue" to support null for the second parameter of WeakReference(Object,ReferenceQueue) on all platforms3.
java.lang.reflect AccessibleObject * (4 new methods)  
AnnotatedElement2 *  
Constructor * (11 new methods)  
Field * (8 new methods)  
GenericArrayType *  
GenericDeclaration2 *  
GenericSignatureFormatError *  
MalformedParameterizedTypeException *  
Member * (1 new method)  
Method * (14 new methods)  
ParameterizedType *  
Type2 *  
TypeVariable *  
WildcardType *  
java.math BigDecimal ZERO, ONE, TEN,
BigDecimal(int),
BigDecimal(long),
BigDecimal(char[]),
BigDecimal(char[], int, int),
divide(BigDecimal),
divideAndRemainder(BigDecimal),
divideToIntegralValue(BigDecimal),
pow(int),
remainder(BigDecimal),
stripTrailingZeros(),
toPlainString(),
valueOf(double),
valueOf(long)
Enable feature "BigDecimal.setScale" to support negative scales in the BigDecimal.setScale(int, int) method3.
BigInteger TEN  
java.net HttpURLConnection * (6 new methods) Enable features "HttpURLConnection.setChunkedStreamingMode", "HttpURLConnection.setFixedLengthStreamingMode" to use the corresponding methods, but on Java 1.4 they will simply return. Consider using alternative or writing own protocol handlers.
Proxy5 *  
ProxySelector5 *  
Socket3,5 Socket(Proxy) Enable feature "Socket.New" to to call the Socket(Proxy) constructor, but the Proxy parameter will be ignored.
URL5 * (2 new methods) The Proxy parameter is ignored by the URL.openConnection(Proxy) method.
URLConnection * (4 new methods) Enable features "URLConnection.getConnectTimeout", "URLConnection.setConnectTimeout", "URLConnection.getReadTimeout", "URLConnection.setReadTimeout" to use the corresponding methods, but on Java 1.4 they will simply return. Consider using alternative or writing own protocol handlers.
java.nio5 CharBuffer * (4 new methods)  
Charset * (1 new method) The Charset.defaultCharset() method returns UTF-8 if the default charset is unavailable (occurs on JDK 1.4.0).
java.rmi.server RemoteObjectInvocationHandler *  
java.text DecimalFormat * (2 new methods) Enable feature "DecimalFormat.setParseBigDecimal" to support the DecimalFormat.setParseBigDecimal(boolean) method, but parsing and formatting precision will still be limited by the java.lang.Double or java.lang.Long precision3.
java.util AbstractQueue1 *  
ArrayDeque1,4 *  
Arrays * (21 new methods)
copyOf(...)4 (10 methods)
copyOfRange(...)4 (10 methods)
 
Calendar getTimeInMillis()6,
setTimeInMillis(long)6
 
Collections1 * (13 new methods)
newSetFromMap(Map)4,
list(Enumeration)6,
replaceAll(List, Object, Object)6,
swap(List, int, int)6
 
Deque1,2,4 *  
EnumMap *  
EnumSet *  
Formatter *  
LinkedList * (5 new methods)  
PriorityQueue1 *  
Properties * Requires an implementation of JAXP 1.3 for J2SE 1.3.
Queue1,2 *  
Timer * (3 new methods and constructors) Enable feature "Timer.All" to use alternative Timer and TimerTask implementations in order to be able to call Timer(String), Timer(String, boolean), and Timer.purge()3.
UUID *  
java.util.concurrent,
java.util.concurrent.atomic,
java.util.concurrent.locks
almost all classes1 almost all methods The LockSupport class may be unusable due to insufficient performance. The Condition.awaitNanos(long) method has little accuracy guarantees.
java.util.regex5 Matcher quoteReplacement(String),
toMatchResult()
 
MatchResult2 *  
Pattern LITERAL3,
quote(String)
Enable features "Pattern.compile" and "Pattern.matches" to support Java 5.0 features in regular expressions when calling these methods3.
javax.net.ssl5 HttpsURLConnection * (2 new methods)  

1 Supported via the Backport of JSR 166.
2 In most cases this type is being replaced with its base type.
3 Supported only when the corresponding feature is enabled via the support or advanced options.
4 Introduced in Java 6.
5 Not supported on J2SE 1.3.
6 Introduced in Java 1.4 and supported on J2SE 1.3.

How to write an extension?

In order to support the API unavailable on the target platform Retrotranslator should be able to replace all references to new classes, constructors, methods, and fields with references to backports compatible with the platform. The location of the backports must be specified with the classpath option. The default backports for the 1.4 target have been packaged into the retrotranslator-runtime-n.n.n.jar and backport-util-concurrent-n.n.jar files, and to complement or override them additional backport names can be specified via the backport option or a properties file. The backport names can have five different forms, the first one declares a universal backport package and the others allow reusing existing backports.

Backport name form Example
<universal backport package name> net.sf.retrotranslator.runtime
com.mycompany.backport
<original package name>:<backport package name> java.util.concurrent:edu.emory.mathcs.backport.java.util.concurrent
com.sun.org.apache.xerces.internal:org.apache.xerces
<original class name>:<backport class name> java.lang.StringBuilder:java.lang.StringBuffer
java.util.LinkedHashMap:org.apache.commons.collections.map.LinkedMap
<original method name>:<backport method name> java.lang.System.nanoTime:edu.emory.mathcs.backport.java.util.concurrent.helpers.Utils.nanoTime
<original field name>:<backport field name> java.util.Collections.EMPTY_MAP:edu.emory.mathcs.backport.java.util.Collections.EMPTY_MAP

The names of backport classes in a universal backport package consist of the backport package name, the name of the original class, and an optional trailing underscore. For example, net.sf.retrotranslator.runtime.java.util.EnumSet_ is a complete backport of java.util.EnumSet. But when classes exist on the target platform then the backports of their new fields, constructors and methods are grouped into classes with a leading underscore in their names. Look at the net.sf.retrotranslator.runtime.java.math._BigDecimal class:

The net.sf.retrotranslator.runtime.java.io._PrintStream and net.sf.retrotranslator.runtime.java.lang._SecurityException classes use another type of constructor backports. There is a public static createInstanceBuilder method that accepts constructor's arguments an returns an object with public argument1...argumentN methods and an optional public void initialize method. All the argumentX methods don't have any parameters and provide arguments for a constructor that exists on the target platform. The initialize method has a single parameter for the created instance and can be used for postprocessing. And the most flexible but unsupported in certain cases way has been used by net.sf.retrotranslator.runtime.java.lang._StackTraceElement.

If backported methods require access to non-public methods or fields of the instance, they can do it with reflection when the security manager allows such access. The backports of public instance fields are not supported, but private instance fields can be emulated using a weak identity map, see net.sf.retrotranslator.runtime.java.lang._Thread for an example.

What are the limitations?

Alternative tools

Contact

License

    Copyright (c) 2005 - 2009 Taras Puchko
    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
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       notice, this list of conditions and the following disclaimer in the
       documentation and/or other materials provided with the distribution.
    3. Neither the name of the copyright holders nor the names of its
       contributors may be used to endorse or promote products derived from
       this software without specific prior written permission.

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