Java from Perl; Perl from Java
From JmPm
Contents |
Perl - Java Similarities
- Interpreted languages
- Platform independent (write once run anywhere)
- Similar syntax (procedural languages)
- Garbage collector
- Modules and packages structure
Differences
- Java 100% object oriented, in Perl OO is optional (function overloading does not exist)
- Java requires compilation, Perl doesn’t
- Java does not allow multiple inheritance, Perl does. (Object == UNIVERSAL)
- Java has strong typing ( requires variable declaration ), Perl has not – variable gets it type after first assignment.
- autoload mechanism
- Do we need strong typing? (strong testing ?)
- Java is rigid, Perl has many ways to say same thing
- Perl has many shell like features (variable interpolation, file test operators). Java has none.
- In Java execution starts in main(), Perl has no main, (__DATA__ feature)
- Perl is much FASTER in development and execution
Why do we need it ?
- Legacy components access
- Code transition from some language to perl
- Speed (C , not Java)
- Component exist in other language and we want to use it in Perl
Inline
- Inline, Inline::Java
- Easy installation
- Short learning curve
- Hides all details (compilation, glue files)
- Inline has extension to many other languages – C , C++ , Python ...
- Older tools XS, SWIG.
• Manual steps, long learning curve, only perl to XXX direction
Perl2Java
- Methods invocation ( regular and static )
- Member variables access
- Study
- Script or package code layout
inline::java steps
- Creates java source file from the embedded code ( Hi.java )
- Compiles java class ( Hi.java -> Hi.class )
- Extracts the methods signatures to Hi.jdat file
Java2Perl
- Implemented by Inline::Java::PerlInterpreter
- Alternative implementation based on
- JNI defines a standard naming and calling convention so the Java virtual machine can locate and invoke native methods
- perl from C invocation , modified examples code from O’Reilly Advanced Perl Programming
- Two basic problems :
- Functions in perl can be called with variable number of parameters and output variable number of values
- Parameters can have different types
