Examples of org.apache.commons.el.ExpressionEvaluatorImpl

org.apache.commons.el.ExpressionEvaluatorImpl

This is the main class for evaluating expression Strings. An expression String is a String that may contain expressions of the form ${...}. Multiple expressions may appear in the same expression String. In such a case, the expression String's value is computed by concatenating the String values of those evaluated expressions and any intervening non-expression text, then converting the resulting String to the expected type using the PropertyEditor mechanism.
In the special case where the expression String is a single expression, the value of the expression String is determined by evaluating the expression, without any intervening conversion to a String.
The evaluator maintains a cache mapping expression Strings to their parsed results. For expression Strings containing no expression elements, it maintains a cache mapping ExpectedType/ExpressionString to parsed value, so that static expression Strings won't have to go through a conversion step every time they are used. All instances of the evaluator share the same cache. The cache may be bypassed by setting a flag on the evaluator's constructor.
The evaluator must be passed a VariableResolver in its constructor. The VariableResolver is used to resolve variable names encountered in expressions, and can also be used to implement "implicit objects" that are always present in the namespace. Different applications will have different policies for variable lookups and implicit objects - these differences can be encapsulated in the VariableResolver passed to the evaluator's constructor.
Most VariableResolvers will need to perform their resolution against some context. For example, a JSP environment needs a PageContext to resolve variables. The evaluate() method takes a generic Object context which is eventually passed to the VariableResolver - the VariableResolver is responsible for casting the context to the proper type.
Once an evaluator instance has been constructed, it may be used multiple times, and may be used by multiple simultaneous Threads. In other words, an evaluator instance is well-suited for use as a singleton. @author Nathan Abramson - Art Technology Group @author Shawn Bayern @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: luehe $


    /**
     * Constructor.
     */
    public ELEvaluator() {
        ee = new ExpressionEvaluatorImpl();
    }

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     *
     * @param fnMapper The function mapper for this Evaluator.
     * @see javax.servlet.jsp.el.FunctionMapper
     */
    public ELEvaluator(final FunctionMapper fnMapper) {
        ee = new ExpressionEvaluatorImpl();
        this.fnMapper = fnMapper;
    }

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     *
     * @return Log The log being used.
     */
    private ExpressionEvaluator getEvaluator() {
        if (ee == null) {
            ee = new ExpressionEvaluatorImpl();
        }
        return ee;
    }

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                throw ValidationException.required(nameText, "Please enter a name.");
            }
            if ((uriText.getText().length() == 0) && !editingDefault) {
                throw ValidationException.required(uriText, "Please enter a URL.");
            }
            ExpressionEvaluator eval = new ExpressionEvaluatorImpl();
            try {
                eval.evaluate((String) nameText.getText(), String.class, new DefaultVariables(),
                              StaticFunctionMapper.getDefault());
            } catch (Exception e) {
                throw ValidationException.invalid(nameText, "Error evaluating EL expression:\n" + e.getMessage());
            }
            try {
                eval.evaluate((String) uriText.getText(), String.class, new DefaultVariables(),
                              StaticFunctionMapper.getDefault());
            } catch (Exception e) {
                throw ValidationException.invalid(uriText, "Error evaluating EL expression:\n" + e.getMessage());
            }

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    }


    public void actionPerformed(ActionEvent ev) {
      try {
        StaticFunctionMapper functionMapper = StaticFunctionMapper.getDefault();
        ExpressionEvaluator eval = new ExpressionEvaluatorImpl();
        VariableResolver resolver = new DefaultVariables(uriText.getText(), null, null);
        resultText.setText((String) eval.evaluate(elText.getText(), String.class, resolver, functionMapper));
      } catch (ELException e) {
        ExceptionDialog.show(TestingTool.this, e);
      }
    }

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    this.log = log;
  }


  // JavaDoc inherited
  public void handle(String data, ContentHandler handler) {
    ExpressionEvaluator evaluator = new ExpressionEvaluatorImpl();
    Object value;
    try {
      value = evaluator.evaluate(data, Object.class, resolver, mapper);
      if (value != null) {
        char[] result = value.toString().toCharArray();
        handler.characters(result, 0, result.length);
      } else {
        log.debug("Failed to resolve " + data);

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        this.log = log;
    }


    // JavaDoc inherited
    public void handle(String data, ContentHandler handler) {
        ExpressionEvaluator evaluator = new ExpressionEvaluatorImpl();
        Object value;
        try {
            value = evaluator.evaluate(data, Object.class, resolver, mapper);
            char[] result = value.toString().toCharArray();
            handler.characters(result, 0, result.length);
        } catch (ELException ele) {
            log.error("Failed to handle EL expression.", ele);
        } catch (SAXException saxe) {

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   *
   * @param data DOCUMENT ME!
   * @param handler DOCUMENT ME!
   */
  public void handle(String data, ContentHandler handler) {
    ExpressionEvaluator evaluator = new ExpressionEvaluatorImpl();
    Object value;


    try {
      value = evaluator.evaluate(data, Object.class, resolver, mapper);


      if (value != null) {
        char[] result = value.toString().toCharArray();
        handler.characters(result, 0, result.length);
      } else {

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    String expr = expr_.replaceAll("\\#\\{", "\\$\\{");
    Object value = null;
    if (retType == null) {
      retType = java.lang.String.class;
    }
    ExpressionEvaluatorImpl exprEvaluator = new ExpressionEvaluatorImpl();
    VariableResolver varResolver = ctx.getVariableResolver();
    try {
      value = exprEvaluator.evaluate(expr, retType, varResolver, null);
    } catch (javax.servlet.jsp.el.ELException e) {
      MessageFormat msgFormat = new MessageFormat(ERR_BAD_EXPR);
          log.warn(msgFormat.format(new Object[] {e.getMessage()}));
      return null;
    } // end of try-catch

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   *
   * @param data DOCUMENT ME!
   * @param handler DOCUMENT ME!
   */
  public void handle(String data, ContentHandler handler) {
    ExpressionEvaluator evaluator = new ExpressionEvaluatorImpl();
    Object              value;


    try {
      value                       = evaluator.evaluate(data, Object.class, resolver, mapper);


      if (value != null) {
        char[] result = value.toString().toCharArray();
        handler.characters(result, 0, result.length);
      } else {

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