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

    All Methods Static Methods Concrete 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

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