Condition.java

/*
Copyright (c) 2008 Health Market Science, Inc.

Licensed 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

    http://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 com.healthmarketscience.sqlbuilder;

import java.io.IOException;

import com.healthmarketscience.common.util.AppendableExt;


/**
 * An object representing a conditional expression.
 *
 * @author James Ahlborn
 */
public abstract class Condition extends NestableClause
{
  /** a Condition object which will always return <code>true</code> for
      {@link Condition#isEmpty}.  useful for selectively including condition
      blocks */
  public static final Condition EMPTY = new Condition() {
      @Override
      public boolean isEmpty() { return true; }
      @Override
      protected void collectSchemaObjects(ValidationContext vContext) {}
      @Override
      public void appendTo(AppendableExt app) throws IOException {
        throw new UnsupportedOperationException("Should never be called");
      }
    };

  
  protected Condition() {}

  @Override
  public Condition setDisableParens(boolean disableParens) {
    super.setDisableParens(disableParens);
    return this;
  }  
}