| Description |
Janino is a compiler that reads a Java expression, block, or source file, and generates Java bytecode that is loaded and executed directly. It is not intended to be a development tool, but an embedded compiler for run-time compilation purposes, such as expression evaluators or"server pages"engines like JSP.
Properties
The major design goal was to keep the compiler small and simple, while partially sacrificing completeness. I don't like the idea of carrying around huge libraries for simple applications. See Parser for the list of implemented and missing language features.
When do you need an efficient expression evaluator?
Say you build an e-commerce system, which computes the shipping cost for the items that the user put into his/her shopping cart. Because you don't know the merchant's shipping cost model at implementation time, you could implement a set of shipping cost models that come to mind (flat charge, by weight, by number of items, ...) and select one of those at run-time.
In practice, you will most certainly find that the shipping cost models you implemented will rarely match what the merchant wants, so you must add custom models, which are merchant-specific. If the merchant's model changes later, you must change your code, re-compile and re-distribute your software.
Because this is so unflexible, the shipping cost expression should be specified at run-time, not at compile-time. This implies that the expression must be scanned, parsed and evaluated at run-time, which is why you need an expression evaluator.
A simple expression evaluator would parse an expression and create a"syntax tree". The expression"a + b * c", for example, would compile into a"Sum"object who's first operand is parameter"a"and who's second operand is a"Product"object who's operands are parameters"b"and"c". Such a syntax tree can evaluated relatively quickly. However, the run-time performance is about a factor of 100 worse than that of native Java code. |
| Supported languages: English |
| Supported OS: Win95, Win98, WinME, WinNT 3.x, WinNT 4.x, Windows2000, WinXP, Unix, Linux, Mac PPC |
| Installation: No Install Support |
| Requirements: JDK 1.3.1 or above |
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| Release info |
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11/09/2002
Minor Update
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Changes:
Updated the overview page.
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| License info |
| License: Freeware |
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| End user license agreement |
Janino - An embedded Java[TM] compiler
Copyright (c) 2005, Arno Unkrig
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following
disclaimer in the documentation and/or other materials
provided with the distribution.
3. The name of the author may not be used to endorse or promote
products derived from this software without specific prior
written permission.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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