org.apache.lucene.expressions.js

Class JavascriptCompiler

java.lang.Object

org.apache.lucene.expressions.js.JavascriptCompiler

public final class JavascriptCompiler
extends Object

An expression compiler for javascript expressions.

Example:

   Expression foo = JavascriptCompiler.compile("((0.3*popularity)/10.0)+(0.7*score)");
 

See the package documentation for the supported syntax and default functions.

You can compile with an alternate set of functions via compile(String, Map, ClassLoader). For example:

   Map<String,Method> functions = new HashMap<>();
   // add all the default functions
   functions.putAll(JavascriptCompiler.DEFAULT_FUNCTIONS);
   // add cbrt()
   functions.put("cbrt", Math.class.getMethod("cbrt", double.class));
   // call compile with customized function map
   Expression foo = JavascriptCompiler.compile("cbrt(score)+ln(popularity)", 
                                               functions, 
                                               getClass().getClassLoader());
 

WARNING: This API is experimental and might change in incompatible ways in the next release.

Field Summary

Fields

Modifier and Type	Field and Description
static Map<String,Method>	DEFAULT_FUNCTIONS The default set of functions available to expressions.

Method Summary

Methods

Modifier and Type	Method and Description
static Expression	compile(String sourceText) Compiles the given expression.
static Expression	compile(String sourceText, Map<String,Method> functions, ClassLoader parent) Compiles the given expression with the supplied custom functions.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_FUNCTIONS

public static final Map<String,Method> DEFAULT_FUNCTIONS

The default set of functions available to expressions.

See the package documentation for a list.

Method Detail

compile

public static Expression compile(String sourceText)
                          throws ParseException

Compiles the given expression.

Parameters:

sourceText - The expression to compile

Returns:

A new compiled expression

Throws:

ParseException - on failure to compile

compile

public static Expression compile(String sourceText,
                 Map<String,Method> functions,
                 ClassLoader parent)
                          throws ParseException

Compiles the given expression with the supplied custom functions.

Functions must be public static, return double and can take from zero to 256 double parameters.

Parameters:

sourceText - The expression to compile

functions - map of String names to functions

parent - a ClassLoader that should be used as the parent of the loaded class. It must contain all classes referred to by the given functions.

Returns:

A new compiled expression

Throws:

ParseException - on failure to compile