jdx (version 0.1.4)

convertToRlowLevel: Low-level Interface for jdx

Description

The functions listed here are the low-level interface for jdx and are primarily used behind the scenes in jsr223, the high-level integration package for Java. However, these functions may also be useful for rJava developers interested in a thread-safe alternative to convertToR. See the code examples for a brief outline. If multi-threaded access is not required, please use convertToR.

Usage

arrayOrderToString(value)
convertToRlowLevel(
  j2r,
  data.code = NULL,
  strings.as.factors = NULL
)
createJavaToRobject()
jdxConstants()
processCompositeDataCode(
  j2r,
  composite.data.code,
  throw.exceptions = TRUE,
  warn.missing.logical = TRUE,
  warn.missing.raw = TRUE
)

Arguments

value

An rJava object reference to a org.fgilbert.jdx.JavaToR$ArrayOrder enumeration value.

j2r

An rJava object reference to a org.fgilbert.jdx.JavaToR object. The createJavaToRobject function creates an instance.

data.code

A jdx data code value created with processCompositeDataCode.

strings.as.factors

Same as in convertToR.

composite.data.code

A jdx composite data code returned by the initialize method of org.fgilbert.jdx.JavaToR.

throw.exceptions

A logical value indicating whether to throw exceptions.

warn.missing.logical

A logical value indicating whether to raise a specific warning.

warn.missing.raw

A logical value indicating whether to raise a specific warning.

Details

See the code examples below for a thread-safe alternative to convertToR. The low-level functional interface presented here is awkward, but it was designed to limit type inference and the number of transactions between R and the JVM, ultimately maximizing performance for jsr223.

See Also

convertToJava , convertToR , getJavaClassName

Examples

# NOT RUN {
library("jdx")

# Create org.fgilbert.jdx.JavaToR object used to convert 
# java objects to R objects. Create one of these objects
# per thread for thread-safe execution.
# 
# It is also possible to create and use the JavaToR
# object in Java and return a reference to R via rJava.
j2r <- createJavaToRobject()

# Pass the Java object to be converted to the initialize 
# method of the JavaToR object. Note that the Java object
# must be cast as java.lang.Object. The initialize method
# returns an integer value known as a composite data code
# that is used to derive the R structure.
composite.data.code <- rJava::.jcall(
  j2r
  , "I"
  , "initialize"
  , rJava::.jcast(convertToJava(iris))
)

# Process the resulting composite data code to get a data
# code vector. This step also raises any applicable 
# errors/warnings.
data.code <- processCompositeDataCode(j2r, composite.data.code)

# Pass the JavaToR object and the data code to
# convertToRlowLevel to get the R object.
convertToRlowLevel(j2r, data.code, strings.as.factors = FALSE)

# When converting n-dimensional arrays, pass an array 
# ordering constant to the initialize method.
array.order.constants <- jdxConstants()$ARRAY_ORDER
array <- convertToJava(as.matrix(iris[1:4]), array.order = "column-major")
composite.data.code <- rJava::.jcall(
  j2r
  , "I"
  , "initialize"
  , rJava::.jcast(array)
  , array.order.constants[["column-major"]]
)
data.code <- processCompositeDataCode(j2r, composite.data.code)
convertToRlowLevel(j2r, data.code)
# }