Package org.apache.lucene.expressions.js
Class JavascriptCompiler
java.lang.Object
org.apache.lucene.expressions.js.JavascriptCompiler
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.
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Field Summary
FieldsModifier and TypeFieldDescriptionstatic final Map<String, MethodHandle> The default set of functions available to expressions. -
Method Summary
Modifier and TypeMethodDescriptionstatic ExpressionCompiles the given expression using default compiler settings.static Expressioncompile(String sourceText, Map<String, MethodHandle> functions) Compiles the given expression with the supplied custom functions using default compiler settings.static Map<String, MethodHandle> convertLegacyFunctions(Map<String, Method> functions) Deprecated.Only use this to convert Lucene 9.x or earlier legacy code.
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Field Details
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DEFAULT_FUNCTIONS
The default set of functions available to expressions.See the
package documentationfor a list.
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Method Details
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compile
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
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compile
public static Expression compile(String sourceText, Map<String, MethodHandle> functions) throws ParseExceptionCompiles the given expression with the supplied custom functions using default compiler settings.Functions must be
public static, returndoubleand can take from zero to 256doubleparameters.- Parameters:
sourceText- The expression to compilefunctions- map of String names toMethodHandles- Returns:
- A new compiled expression
- Throws:
ParseException- on failure to compile
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convertLegacyFunctions
@Deprecated public static Map<String,MethodHandle> convertLegacyFunctions(Map<String, Method> functions) throws IllegalAccessExceptionDeprecated.Only use this to convert Lucene 9.x or earlier legacy code. For new code useMethodHandle.Converts a legacy map with reflectiveMethodfunctions toMap<String,MethodHandlefor use withcompile(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 infunctionsare not accessible by the publicMethodHandles.Lookup.
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