Created by Alan Ruttenberg
JSS stands for either "Java Simple Syntax" or "Java Syntax Sucks", depending on your mood.
The dynamic dispatch of the java.lang.reflect package is used to make it real easy, if perhaps less efficient, to write Java code since you don't need to be bothered with imports, or with figuring out which method to call. The only time that you need to know a class name is when you want to call a static method, or a constructor, and in those cases, you only need to know enough of the class name that is unique wrt to the classes on your classpath.
Java methods look like this: #"toString". Java classes are represented as symbols, which are resolved to the appropriate java class name. When ambiguous, you need to be more specific. A simple example from CL-USER:
(require :jss)
(let ((sw (new 'StringWriter)))
(#"write" sw "Hello ")
(#"write" sw "World")
(print (#"toString" sw)))
What's happened here? First, all the classes in all the jars in the classpath have been collected. For each class a.b.C.d, we have recorded that b.c.d, b.C.d, C.d, c.d, and d potentially refer to this class. In your call to new, as long as the symbol can refer to only one class, we use that class. In this case, it is java.io.StringWriter. You could also have written
(new 'io.stringwriter)
or
(new '|io.StringWriter|)
or
(new 'java.io.StringWriter)
The call
(#"write" sw "Hello ")
uses the code in invoke.java to call the method named "write" with the arguments sw and "Hello ". JSS figures out the right java method to call, and calls it.
An interactive restart is available to resolve class ambiguity.
Static calls are possible as well with the SHARPSIGN-QUOTATION_MARK macro, but the first argument must be a symbol to distinguish
(#"getProperties" "java.lang.System")
from
(#"getProperties" 'java.lang.System)
The first attempts to call a method on the java.lang.String object with the contents "java.lang.System", which results in an error, while the second invokes the static java.lang.System.getProperties() method.
If you want to do a raw java call, use #0"toString". Raw calls return their results as Java objects, avoiding doing the usual Java object to Lisp object conversions that ABCL does.
(with-constant-signature ((name jname raw?)*) &body body)
binds a macro which expands to a jcall, promising that the same method will be called every time. Use this if you are making a lot of calls and want to avoid the overhead of a the dynamic dispatch. e.g.
(with-constant-signature ((tostring "toString"))
(time (dotimes (i 10000) (tostring "foo"))))
runs about three times faster than
(time (dotimes (i 10000) (#"toString" "foo")))
So, something like
(with-constant-signature
((tostring "toString" t)) ...)
will cause the toString to be a raw java call. See JSS::GET-ALL-JAR-CLASSNAMES for an example.
Implementation is that the first time the function is called, the method is looked up based on the arguments passed, and thereafter that method is called directly. Doesn't work for static methods at the moment (lazy)
(japropos string)
finds all class names matching STRING.
(jcmn class-name)
lists the names of all methods for the CLASS-NAME.
Java static fields may be addressed via the SHARPSIGN-QUOTATION_MARK macro as
(#"java.lang.System.out")
Java fields can by dynamically accessed with
(let ((class 'java.lang.system)
(field "out"))
#"{class}.{field}")
Use #1"" to use JAVAPARSER to parse an expression. JAVAPARSER will be loaded on first use.
(#1"new ByteBuddy()
.subclass(Object.class,t)
.method(ElementMatchers.named("toString"))
.intercept(FixedValue.value("Hello World!"))
.make()
.load(getClass().getClassLoader())
.getLoaded()"
The function ENSURE-COMPATIBILITY attempts to provide a compatibility mode to existing users of JSS by importing the necessary symbols into CL-USER.
Some notes on other compatibility issues:
classpath-manager
Since we are no longer using Beanshell, this is no longer present. For obtaining the current classloader use JAVA:CLASSLOADER.
1.0 Equivalent to Alan Ruttenberg's version included with the original lsw2.
3.0 The results the of having JSS package loaded from abcl-contrib
<> dc:created "2005" ;
dc:author "Mark <evenson.not.org@gmail.com>";
dc:revised "11-JUN-2017" .