jcall: Call a Java method

Description

.jcall calls a Java method with the supplied arguments.

Usage

.jcall(obj, returnSig = "V", method, ..., evalArray = TRUE, 
    evalString = TRUE, interface = "RcallMethod")

Arguments

obj

Java object (jobjRef as returned by .jcall or .jnew) or fully qualified class name in JNI notation (e.g. "java/lang/String").

returnSig

Return signature in JNI notation (e.g. "V" for void, "[I" for int[] etc.). For convenience additional type "S" is supported and expanded to "Ljava/lang/String;".

method

The name of the method to be called

...

Any parametes that will be passed to the Java method. The parameter types are determined automatically and/or taken from the jobjRef object.

evalArray

This flag determines whether the array return value is evaluated (TRUE) or passed back as Java object reference (FALSE).

evalString

This flag determines whether string result is returned as characters or as Java object reference.

interface

This option is experimental and specifies the interface used for calling the Java method; the current implementation supports two interfaces:

"RcallMethod"

{the default interface.} "RcallSyncMeth

Value

Returns the result of the method.

Details

.jcall requires exact match of argument and return types. For higher efficiency .jcall doens't perform any lookup in the reflection tables. This means that passing subclasses of the classes present in the method definition requires explicit casting using .jcast. Passing null arguments also needs a proper class specification with .jnull.

Examples

Run this code

.jcall("java/lang/System","S","getProperty","os.name")
f <- .jnew("java/awt/Frame","Hello")
.jcall(f,,"setVisible",TRUE)

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