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JSR-000372: JavaServer(TM) Faces 2.3 API
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/*
 * Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package javax.faces.validator;

import java.util.Map;
import javax.el.ELContext;
import javax.el.ELException;
import javax.el.MethodExpression;
import javax.faces.component.StateHolder;
import javax.faces.component.UIComponent;
import javax.faces.context.ExternalContext;
import javax.faces.context.FacesContext;

/**
 * MethodExpressionValidator
 * is a {@link Validator} that wraps a {@link MethodExpression}, and it
 * performs validation by executing a method on an object identified by
 * the {@link MethodExpression}.
 */

public class MethodExpressionValidator implements Validator, StateHolder {

    private static final String BEANS_VALIDATION_AVAILABLE =
            "javax.faces.private.BEANS_VALIDATION_AVAILABLE";
    
    private static final String VALIDATE_EMPTY_FIELDS_PARAM_NAME = 
            "javax.faces.VALIDATE_EMPTY_FIELDS";
    
    // ------------------------------------------------------ Instance Variables

    private MethodExpression methodExpression = null;

    private Boolean validateEmptyFields;
    
    public MethodExpressionValidator() {

        super();

    }

    /**
     * Construct a {@link Validator} that contains a {@link MethodExpression}.
     *
     * @param methodExpression the expression to wrap
     */
    public MethodExpressionValidator(MethodExpression methodExpression) {

        super();
        this.methodExpression = methodExpression;

    }

    // ------------------------------------------------------- Validator Methods

    /**
     * @throws NullPointerException {@inheritDoc}
     * @throws ValidatorException   {@inheritDoc}
     */
    @Override
    public void validate(FacesContext context,
                         UIComponent component,
                         Object value) throws ValidatorException {

        if ((context == null) || (component == null)) {
            throw new NullPointerException();
        }
        if (validateEmptyFields(context) || value != null) {
            try {
                ELContext elContext = context.getELContext();
                methodExpression.invoke(elContext, new Object[]{context, component, value});
            } catch (ELException ee) {
                Throwable e = ee.getCause();
                if (e instanceof ValidatorException) {
                    throw (ValidatorException) e;
                } else {
                    throw ee;
                }
            }
        }
    }

    // ----------------------------------------------------- StateHolder Methods


    @Override
    public Object saveState(FacesContext context) {
        if (context == null) {
            throw new NullPointerException();
        }
        Object values[] = new Object[1];
        values[0] = methodExpression;
        return (values);

    }


    @Override
    public void restoreState(FacesContext context, Object state) {
        if (context == null) {
            throw new NullPointerException();
        }
        if (state == null) {
            return;
        }
        Object values[] = (Object[]) state;
        methodExpression = (MethodExpression) values[0];
    }


    private boolean transientValue;


    @Override
    public boolean isTransient() {

        return (this.transientValue);

    }


    @Override
    public void setTransient(boolean transientValue) {

        this.transientValue = transientValue;

    }

    private boolean validateEmptyFields(FacesContext ctx) {

        if (validateEmptyFields == null) {
            ExternalContext extCtx = ctx.getExternalContext();
            String val = extCtx.getInitParameter(VALIDATE_EMPTY_FIELDS_PARAM_NAME);

            if (null == val) {
                val = (String) extCtx.getApplicationMap().get(VALIDATE_EMPTY_FIELDS_PARAM_NAME);
            }
            if (val == null || "auto".equals(val)) {
                validateEmptyFields = isBeansValidationAvailable(ctx);
            } else {
                validateEmptyFields = Boolean.valueOf(val);
            }
        }

        return validateEmptyFields;

    }

    private boolean isBeansValidationAvailable(FacesContext context) {
        boolean result = false;

        Map appMap = context.getExternalContext().getApplicationMap();
        
        if (appMap.containsKey(BEANS_VALIDATION_AVAILABLE)) {
            result = (Boolean) appMap.get(BEANS_VALIDATION_AVAILABLE);
        } else {
            try {
                new BeanValidator();
                appMap.put(BEANS_VALIDATION_AVAILABLE, Boolean.TRUE);
                result = true;
            } catch (Throwable t) {
                appMap.put(BEANS_VALIDATION_AVAILABLE, Boolean.FALSE);
            }
        }

        return result;
    }
}