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   *   Licensed to the Apache Software Foundation (ASF) under one
   *  or more contributor license agreements.  See the NOTICE file
   *  distributed with this work for additional information
   *  regarding copyright ownership.  The ASF licenses this file
   *  to you under the Apache License, Version 2.0 (the
   *  "License"); you may not use this file except in compliance
   *  with the License.  You may obtain a copy of the License at
   *
   *    https://www.apache.org/licenses/LICENSE-2.0
   *
   *  Unless required by applicable law or agreed to in writing,
   *  software distributed under the License is distributed on an
   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   *  KIND, either express or implied.  See the License for the
   *  specific language governing permissions and limitations
   *  under the License.
   ****************************************************************/
  
  package org.apache.cayenne.swing;
  
  import ognl.Ognl;
  import ognl.OgnlException;
  
  import org.apache.cayenne.CayenneRuntimeException;
  import org.apache.cayenne.util.Util;
  import org.apache.cayenne.validation.ValidationException;
  
  /**
   */
  public abstract class BindingBase implements ObjectBinding {
  
      private Object compiled;
  
      protected Object context;
      protected String expression;
  
      protected BindingDelegate delegate;
      protected boolean modelUpdateDisabled;
  
      protected boolean usingNullForEmptyStrings;
      protected boolean checkingForValueChange;
  
      static Throwable unwind(Throwable th) {
          if (th instanceof OgnlException) {
              Throwable reason = ((OgnlException) th).getReason();
              return (reason != null) ? unwind(reason) : th;
          } else {
              return Util.unwindException(th);
          }
      }
  
      public BindingBase(String propertyExpression) {
  
          try {
              this.compiled = Ognl.parseExpression(propertyExpression);
          } catch (OgnlException ex) {
              throw new CayenneRuntimeException("Invalid expression - "
                      + propertyExpression, BindingBase.unwind(ex));
          }
  
          this.expression = propertyExpression;
      }
  
      public Object getContext() {
          return context;
      }
  
      public void setContext(Object object) {
          this.context = object;
      }
  
      public boolean isCheckingForValueChange() {
          return checkingForValueChange;
      }
  
      public void setCheckingForValueChange(boolean checkingForValueChange) {
          this.checkingForValueChange = checkingForValueChange;
      }
  
      public boolean isUsingNullForEmptyStrings() {
          return usingNullForEmptyStrings;
      }
  
      public void setUsingNullForEmptyStrings(boolean b) {
          this.usingNullForEmptyStrings = b;
      }
  
      public String getExpression() {
          return expression;
      }
  
      public BindingDelegate getDelegate() {
          return delegate;
      }
  
      public void setDelegate(BindingDelegate delegate) {
          this.delegate = delegate;
      }
  
      /**
       * Pushes a new value to the bound context. If binding delegate is set, notifies it
       * delegate about the update.
       */
      public void setValue(Object value) {
          if (context == null) {
              throw new BindingException("No context");
          }
  
          try {
              // prevent the same thread from calling setValue recursively - something that
              // may happen due to event loops.
  
              if (modelUpdateDisabled) {
                  return;
              }
  
              Object oldValue = null;
  
              modelUpdateDisabled = true;
              try {
  
                  if (delegate != null) {
                      // find old value
                      oldValue = getValue();
                  }
  
                  if (isUsingNullForEmptyStrings() && "".equals(value)) {
                      value = null;
                  }
  
                  if (isCheckingForValueChange()) {
                      // avoid calling getValue() twice...
  
                      Object existingValue = (delegate != null) ? oldValue : getValue();
                      if (Util.nullSafeEquals(value, existingValue)) {
                          return;
                      }
                  }
  
                  Ognl.setValue(compiled, context, value);
              } finally {
                  modelUpdateDisabled = false;
              }
  
              if (delegate != null) {
                  delegate.modelUpdated(this, oldValue, value);
              }
          } catch (OgnlException ex) {
              processException(ex);
          }
      }
  
      /**
       * Pulls bound value from the context.
       */
      public Object getValue() {
          if (context == null) {
              throw new BindingException("No context");
          }
  
          try {
              return Ognl.getValue(compiled, context);
          } catch (OgnlException ex) {
              processException(ex);
              return null;
          }
      }
  
      protected void processException(Throwable th) throws ValidationException, BindingException {
          Throwable root = BindingBase.unwind(th);
          if (root instanceof ValidationException) {
              throw (ValidationException) root;
          } else if (root instanceof NumberFormatException) {
              throw new ValidationException("Invalid numeric string");
          }
  
          throw new BindingException("Evaluation failed in context: " + context, root);
      }
  
  }
  