Java in Functions and Closures

Sometimes you need raw Java performance or want to use Java APIs that don't translate well to CFML. With type="java" you can write actual Java code inside a CFML function - the function body is compiled as Java, not CFML.

This is useful for:

• Performance-critical code (Java compiles to optimized bytecode)
• Implementing Java functional interfaces (lambdas) to pass to Java libraries
• Using Java syntax you're already familiar with

Note: Without a JDK, Lucee uses the Janino compiler which has some limitations.

Basic Syntax

Add type="java" to any function. The return type and arguments must use Java types (int, String, boolean, etc.), not CFML types:

// Java types: int, not numeric; String, not string
int function doubleIt( int i ) type="java" {
	return i * 2;
}

dump( doubleIt( 5 ) ); // 10

Java exceptions work too:

int function safeDouble( int i ) type="java" {
	if ( i < 0 ) throw new IllegalArgumentException( "Must be positive" );
	return i * 2;
}

In Components

Works the same in CFCs - mix Java and CFML functions freely:

component {
	// Java function
	int function multiply( int a, int b ) type="java" {
		return a * b;
	}

	// Regular CFML function
	function describe( required numeric value ) {
		return "The value is #value#";
	}
}

Java Lambda Functions (Functional Interfaces)

Java 8+ uses "functional interfaces" (interfaces with one method) for lambdas. When your Java function signature matches a functional interface, Lucee can pass it directly to Java code expecting that interface.

Example: Java's IntUnaryOperator is a functional interface with method int applyAsInt(int). A matching CFML function:

// Matches IntUnaryOperator: takes int, returns int
int function triple( int i ) type="java" {
	return i * 3;
}

// Can now pass to Java methods expecting IntUnaryOperator
import java.util.stream.IntStream;
result = IntStream::of( 1, 2, 3 ).map( triple ).sum();
dump( result ); // 18 (3 + 6 + 9)

This lets you use CFML functions with Java's Stream API, CompletableFuture, and other functional Java APIs.

See also

• Java
• <cffunction>