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java-json-tools#93: only initialize Rhino engine if necessary
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Additionally the Regex class was refactored now following the strategy pattern to prevent if / else on every method call. That refactoring also helped solving the issue.

Also add coverage to the class as the Rhino engine has not been unit-tested before if the build has been done with Java 8 - 14.
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@sdoeringNew
sdoeringNew committed Sep 19, 2020
1 parent 5d443f0 commit 9af226f
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Showing 2 changed files with 158 additions and 77 deletions.
196 changes: 119 additions & 77 deletions src/main/java/com/github/fge/jsonschema/core/util/RegexECMA262Helper.java
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Original file line number Diff line number Diff line change
Expand Up @@ -50,9 +50,9 @@
* expressions", just <a href="http://regex.info">buy it</a> :p</p>
*
* <p>As script engine is used either Nashorn or Rhino as its fallback.
* Nashorn is only available on Java 8 runtimes or higher.</p>
* Nashorn is only available on Java 8 up to 14.</p>
*
* <p>Rhino is only the fallback as it is tremendously slower.</p>
* <p>Rhino is the fallback as it is tremendously slower.</p>
*/
@ThreadSafe
public final class RegexECMA262Helper
Expand All @@ -62,8 +62,8 @@ public final class RegexECMA262Helper
private static final String REG_MATCH_FUNCTION_NAME = "regMatch";

/**
* JavaScript scriptlet defining functions {@link #REGEX_IS_VALID}
* and {@link #REG_MATCH}
* JavaScript scriptlet defining functions for validating a regular
* expression and for matching an input against a regular expression.
*/
private static final String jsAsString
= "function " + REGEX_IS_VALID_FUNCTION_NAME + "(re)"
Expand All @@ -81,59 +81,20 @@ public final class RegexECMA262Helper
+ " return new RegExp(re).test(input);"
+ '}';

/**
* Script scope
*/
private static final Scriptable SCOPE;

/**
* Reference to Javascript function for regex validation
*/
private static final Function REGEX_IS_VALID;

/**
* Reference to Javascript function for regex matching
*/
private static final Function REG_MATCH;

private static final Invocable PRIMARY_SCRIPT_ENGINE;
private static final RegexScript REGEX_SCRIPT = determineRegexScript();

private RegexECMA262Helper()
{
}

static {
PRIMARY_SCRIPT_ENGINE = tryResolvePrimaryEngine();

final Context ctx = Context.enter();
private static RegexScript determineRegexScript()
{
try {
SCOPE = ctx.initStandardObjects(null, false);
try {
ctx.evaluateString(SCOPE, jsAsString, "re", 1, null);
} catch(UnsupportedOperationException e) {
// See: http://stackoverflow.com/questions/3859305/problems-using-rhino-on-android
ctx.setOptimizationLevel(-1);
ctx.evaluateString(SCOPE, jsAsString, "re", 1, null);
}
REGEX_IS_VALID = (Function) SCOPE.get(REGEX_IS_VALID_FUNCTION_NAME, SCOPE);
REG_MATCH = (Function) SCOPE.get(REG_MATCH_FUNCTION_NAME, SCOPE);
} finally {
Context.exit();
}
}

private static Invocable tryResolvePrimaryEngine() {
final ScriptEngine engine = new ScriptEngineManager()
.getEngineByName("nashorn");
if(engine != null) {
try {
engine.eval(jsAsString);
return (Invocable) engine;
} catch(final ScriptException e) {
// the script can't be parsed - the script engine can't be used
}
return new NashornScript();
} catch(final ScriptException e) {
// either Nashorn is not available or the JavaScript can't be parsed
}
return null;
return new RhinoScript();
}

/**
Expand All @@ -144,11 +105,7 @@ private static Invocable tryResolvePrimaryEngine() {
*/
public static boolean regexIsValid(final String regex)
{
if(PRIMARY_SCRIPT_ENGINE != null)
{
return invokeScriptEngine(REGEX_IS_VALID_FUNCTION_NAME, regex);
}
return invokeFallbackEngine(REGEX_IS_VALID, regex);
return REGEX_SCRIPT.regexIsValid(regex);
}

/**
Expand All @@ -167,36 +124,121 @@ public static boolean regexIsValid(final String regex)
*/
public static boolean regMatch(final String regex, final String input)
{
if(PRIMARY_SCRIPT_ENGINE != null)
return REGEX_SCRIPT.regMatch(regex, input);
}

private interface RegexScript
{
boolean regexIsValid(String regex);

boolean regMatch(String regex, String input);
}

private static class NashornScript implements RegexScript
{
/**
* Script engine
*/
private final Invocable scriptEngine;

private NashornScript() throws ScriptException
{
final ScriptEngine engine = new ScriptEngineManager()
.getEngineByName("nashorn");
if (engine == null) {
throw new ScriptException("ScriptEngine 'nashorn' not found.");
}
engine.eval(jsAsString);
this.scriptEngine = (Invocable) engine;
}

private boolean invokeScriptEngine(final String function,
final Object... values)
{
try {
return (Boolean) scriptEngine.invokeFunction(function,
values);
} catch(final ScriptException e) {
throw new IllegalStateException(
"Unexpected error on invoking Script.", e);
} catch(final NoSuchMethodException e) {
throw new IllegalStateException(
"Unexpected error on invoking Script.", e);
}
}

@Override
public boolean regexIsValid(final String regex)
{
return invokeScriptEngine(REGEX_IS_VALID_FUNCTION_NAME, regex);
}

@Override
public boolean regMatch(final String regex, final String input)
{
return invokeScriptEngine(REG_MATCH_FUNCTION_NAME, regex, input);
}
return invokeFallbackEngine(REG_MATCH, regex, input);
}

private static boolean invokeScriptEngine(final String function,
final Object... values)
private static class RhinoScript implements RegexScript
{
try {
return (Boolean) PRIMARY_SCRIPT_ENGINE.invokeFunction(function,
values);
} catch(final ScriptException e) {
throw new IllegalStateException(
"Unexpected error on invoking Script.", e);
} catch(final NoSuchMethodException e) {
throw new IllegalStateException(
"Unexpected error on invoking Script.", e);
/**
* Script scope
*/
private final Scriptable scope;

/**
* Reference to Javascript function for regex validation
*/
private final Function regexIsValid;

/**
* Reference to Javascript function for regex matching
*/
private final Function regMatch;

private RhinoScript()
{
final Context ctx = Context.enter();
try {
this.scope = ctx.initStandardObjects(null, false);
try {
ctx.evaluateString(scope, jsAsString, "re", 1, null);
} catch(final UnsupportedOperationException e) {
// See: http://stackoverflow.com/questions/3859305/problems-using-rhino-on-android
ctx.setOptimizationLevel(-1);
ctx.evaluateString(scope, jsAsString, "re", 1, null);
}
this.regexIsValid = (Function)
scope.get(REGEX_IS_VALID_FUNCTION_NAME, scope);
this.regMatch = (Function)
scope.get(REG_MATCH_FUNCTION_NAME, scope);
} finally {
Context.exit();
}
}
}

private static boolean invokeFallbackEngine(final Function function,
final Object... values)
{
final Context context = Context.enter();
try {
return (Boolean) function.call(context, SCOPE, SCOPE, values);
} finally {
Context.exit();
private boolean invokeScriptEngine(final Function function,
final Object... values)
{
final Context context = Context.enter();
try {
return (Boolean) function.call(context, scope, scope, values);
} finally {
Context.exit();
}
}

@Override
public boolean regexIsValid(final String regex)
{
return invokeScriptEngine(regexIsValid, regex);
}

@Override
public boolean regMatch(final String regex, final String input)
{
return invokeScriptEngine(regMatch, regex, input);
}
}
}
39 changes: 39 additions & 0 deletions src/test/java/com/github/fge/jsonschema/core/util/RegexECMA262HelperTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -23,12 +23,49 @@
import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;

import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.Iterator;

import static org.testng.Assert.*;

public final class RegexECMA262HelperTest
{
private static Object rhinoScriptInstance;
private static Method regexIsValid;
private static Method regMatch;

/**
* Depending on the JDK version the Rhino fallback engine will
* not be tested. To ensure functionality for Rhino, too, prepare
* tests for it via reflection.
*/
static
{
try {
final Class<?> rhinoScriptClass = Class.forName(
RegexECMA262Helper.class.getName() + "$RhinoScript");
final Constructor<?> constructor = rhinoScriptClass.getDeclaredConstructor();
constructor.setAccessible(true);
rhinoScriptInstance = constructor.newInstance();
regexIsValid = rhinoScriptInstance.getClass()
.getDeclaredMethod("regexIsValid", String.class);
regMatch = rhinoScriptInstance.getClass()
.getDeclaredMethod("regMatch", String.class, String.class);
} catch (final Exception e) {
throw new IllegalStateException("Can't initialize RhinoScript.", e);
}
}

private static boolean rhinoScript(final Method method, final Object... args)
{
try {
return (boolean) method.invoke(rhinoScriptInstance, args);
} catch (final Exception e) {
throw new IllegalStateException("Can't invoke method on RhinoScript.");
}
}

@DataProvider
public Iterator<Object[]> ecma262regexes()
{
Expand All @@ -51,6 +88,7 @@ public void regexesAreCorrectlyAnalyzed(final String regex,
{
assertEquals(RegexECMA262Helper.regexIsValid(regex), valid);
assertEquals(RhinoHelper.regexIsValid(regex), valid);
assertEquals(rhinoScript(regexIsValid, regex), valid);
}

@DataProvider
Expand All @@ -77,5 +115,6 @@ public void regexMatchingIsDoneCorrectly(final String regex,
{
assertEquals(RegexECMA262Helper.regMatch(regex, input), valid);
assertEquals(RhinoHelper.regMatch(regex, input), valid);
assertEquals(rhinoScript(regMatch, regex, input), valid);
}
}

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