Examples of org.apache.commons.jexl2.JexlEngine

org.apache.commons.jexl2.MapContext
Creates and evaluates Expression and Script objects. Determines the behavior of Expressions & Scripts during their evaluation with respect to:
- Introspection, see {@link Uberspect}
- Arithmetic & comparison, see {@link JexlArithmetic}
- Error reporting
- Logging
The setSilent and setLenient methods allow to fine-tune an engine instance behavior according to various error control needs. The lenient/strict flag tells the engine when and if null as operand is considered an error, the silent/verbose flag tells the engine what to do with the error (log as warning or throw exception).
- When "silent" & "lenient":
  0 & null should be indicators of "default" values so that even in an case of error, something meaningfull can still be inferred; may be convenient for configurations.
- When "silent" & "strict":
  One should probably consider using null as an error case - ie, every object manipulated by JEXL should be valued; the ternary operator, especially the '?:' form can be used to workaround exceptional cases. Use case could be configuration with no implicit values or defaults.
- When "verbose" & "lenient":
  The error control grain is roughly on par with JEXL 1.0
- When "verbose" & "strict":
  The finest error control grain is obtained; it is the closest to Java code - still augmented by "script" capabilities regarding automated conversions & type matching.
Note that methods that evaluate expressions may throw unchecked exceptions; The {@link JexlException} are thrown in "non-silent" mode but since these areRuntimeException, user-code should catch them wherever most appropriate.
@since 2.0

     * <EM>NOTE: The internal JexlEngine instance can be null when this is deserialized.</EM>
     * </P>
     * @return
     */
    private JexlEngine getJexlEngine() {
        JexlEngine engine = jexlEngine;
        if (engine == null) {
            synchronized (this) {
                engine = jexlEngine;
                if (engine == null) {
                    jexlEngine = engine = createJexlEngine();

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        }
        return super.getMethod(obj, method, args, info);
      }
    };


    JexlEngine engine = new JexlEngine(uberspect, null, null, null);
    engine.setStrict(true);
    engine.setClassLoader(cl);
    return engine;
  }

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   * Creates a new JEXL engine instance.
   * 
   * @return a new {@link JexlEngine}
   */
  public static JexlEngine createJexlEngine() {
    return new JexlEngine();
  }

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    private static JexlEngine jexlEngine;


    private static JexlEngine getEngine() {
        synchronized (LOG) {
            if (jexlEngine == null) {
                jexlEngine = new JexlEngine(new ClassFreeUberspectImpl(null), null, null, null);
                jexlEngine.setClassLoader(new EmptyClassLoader());
                jexlEngine.setCache(512);
                jexlEngine.setLenient(true);
                jexlEngine.setSilent(false);
            }

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import java.util.Map;


public class ELUtil {
    public static Object invoke(String expression, Map<String, Object> context) {
        JexlEngine jexl = new JexlEngine();
        Expression el = jexl.createExpression(expression);
        JexlContext elContext = new MapContext();
        for (String property : context.keySet()) {
            elContext.set(property, context.get(property));
        }
        return el.evaluate(elContext);

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    public JexlExpressionParser(final Map<String, Object> vars) {
        if (vars == null) {
            throw new IllegalArgumentException("vars: " + vars);
        }
        engine = new JexlEngine();
        context = new MapContext(vars);


        LOGGER.trace("Using variables: {}", vars);
    }

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  /**
   * Create a new naming strategy using an JEXL expression and the default expression.
   */
  public JexlNamingStrategy() throws JexlException {
    jexl = new JexlEngine();
    this.parsedExpr = jexl.createExpression(DEFAULT_EXPRESSION);
  }

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   * Create a new naming strategy using an JEXL expression and the given expression.
   *
   * @param expr - the JEXL expression to use to create names.
   */
  public JexlNamingStrategy(String expr) throws JexlException {
    jexl = new JexlEngine();
    this.parsedExpr = jexl.createExpression(expr);
  }

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        return null;
    }
    
    /** {@inheritDoc} */
    public String debugString() {
        JexlInfo info = getInfo();
        return info != null? info.debugString() : "";
    }

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        return result;
    }


    public JexlContext addFieldsToContext(final Object attributable, final JexlContext jexlContext) {
        JexlContext context = jexlContext == null
                ? new MapContext()
                : jexlContext;


        final Field[] fields = attributable.getClass().getDeclaredFields();
        for (int i = 0; i < fields.length; i++) {
            try {

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