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

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