Package 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). For example: 

   Map<String,MethodHandle> functions = new HashMap<>();
   // add all the default functions
   functions.putAll(JavascriptCompiler.DEFAULT_FUNCTIONS);
   // add cbrt()
   functions.put("cbrt", MethodHandles.publicLookup().findStatic(Math.class, "cbrt",
                 MethodType.methodType(double.class, double.class)));
   // call compile with customized function map
   Expression foo = JavascriptCompiler.compile("cbrt(score)+ln(popularity)",
                                               functions);

It is possible to pass any MethodHandle as function that only takes double parameters and returns a double. The method does not need to be public, it just needs to be resolved correctly using a private MethodHandles.Lookup instance. Ideally the methods should be static, but you can use MethodHandle.bindTo(Object) to bind it to a receiver.

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

  • Field Details

  • Method Details

    • compile

      public static Expression compile(String sourceText) throws ParseException
      Compiles the given expression using default compiler settings.
      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,MethodHandle> functions) throws ParseException
      Compiles the given expression with the supplied custom functions using default compiler settings.

      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 MethodHandles
      Returns:
      A new compiled expression
      Throws:
      ParseException - on failure to compile

    • convertLegacyFunctions

      @Deprecated public static Map<String,MethodHandle> convertLegacyFunctions(Map<String,Method> functions) throws IllegalAccessException
      Deprecated.
      Only use this to convert Lucene 9.x or earlier legacy code. For new code use MethodHandle.
      Converts a legacy map with reflective Method functions to Map<String,MethodHandle for use with compile(String, Map).
      Parameters:
      functions - a map with only public and accessible reflective methods
      Returns:
      a new (modifiable) map with the same function declarations, but converted to MethodHandle
      Throws:
      IllegalAccessException - if any of the methods in functions are not accessible by the public MethodHandles.Lookup.