UnaryCondition.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;



/**
 * Outputs a unary based condition
 * <code>"(&lt;column&gt; &lt;unaryOp&gt;)"</code> or
 * <code>"(&lt;unaryOp&gt; &lt;column&gt;)"</code>.
 *
 * @author James Ahlborn
 */
public class UnaryCondition extends Condition
{
  /**
   * Interface which can be implemented to provide a custom unary operation.
   */
  public interface CustomUnaryOp
  {
    /** Returns {@code true} if the operator comes before the value, {@code
        false} otherwise. */
    public boolean isPrefixOp();

    /** Returns the Converter which handles the {@code Object} -&gt; {@code
        SqlObject} conversion for the operation value. */
    public Converter<Object,? extends SqlObject> getConverter();
  }
  
  /**
   * Enum representing the unary operations supported in a SQL condition,
   * e.g. <code>"(&lt;column&gt; &lt;unaryOp&gt;)"</code> or
   * <code>"(&lt;unaryOp&gt; &lt;column&gt;)"</code>.
   */
  public enum Op implements CustomUnaryOp
  {
    /** {@code Object} -&gt; {@code SqlObject} conversions handled by
        {@link Converter#COLUMN_VALUE_TO_OBJ}. */
    IS_NULL(" IS NULL", false, Converter.COLUMN_VALUE_TO_OBJ),
    /** {@code Object} -&gt; {@code SqlObject} conversions handled by
        {@link Converter#COLUMN_VALUE_TO_OBJ}. */
    IS_NOT_NULL(" IS NOT NULL", false, Converter.COLUMN_VALUE_TO_OBJ),
    /** {@code Object} -&gt; {@code SqlObject} conversions handled by
        {@link Converter#CUSTOM_TO_SUBQUERY}. */
    EXISTS("EXISTS ", true, Converter.CUSTOM_TO_SUBQUERY),
    /** {@code Object} -&gt; {@code SqlObject} conversions handled by
        {@link Converter#CUSTOM_TO_SUBQUERY}. */
    UNIQUE("UNIQUE ", true, Converter.CUSTOM_TO_SUBQUERY);

    private final String _opStr;
    private final boolean _isPrefixOp;
    private final Converter<Object,? extends SqlObject> _converter;

    private Op(String opStr, boolean isPrefixOp, 
               Converter<Object,? extends SqlObject> converter) {
      _opStr = opStr;
      _isPrefixOp = isPrefixOp;
      _converter = converter;
      
    }

    @Override
    public boolean isPrefixOp() { return _isPrefixOp; }
    
    @Override
    public Converter<Object,? extends SqlObject> getConverter() {
      return _converter; 
    }

    @Override
    public String toString() { return _opStr; }
  }

  
  private CustomUnaryOp _unaryOp;
  private SqlObject _value;

  public UnaryCondition(Op unaryOp, SqlObject obj)
  {
    this(unaryOp, (Object)obj);
  }
    
  /**
   * {@code Object} -&gt; {@code SqlObject} conversions handled by
   * {@link Op#getConverter}.
   */
  public UnaryCondition(Op unaryOp, Object value)
  {
    this((CustomUnaryOp)unaryOp, value);
  }
        
  /**
   * {@code Object} -&gt; {@code SqlObject} conversions handled by
   * {@link CustomUnaryOp#getConverter}.
   */
  public UnaryCondition(CustomUnaryOp unaryOp, Object value)
  {
    _unaryOp = unaryOp;
    _value = _unaryOp.getConverter().convert(value);
  }
        
  @Override
  protected void collectSchemaObjects(ValidationContext vContext) {
    _value.collectSchemaObjects(vContext);
  }
    
  @Override
  public void appendTo(AppendableExt app) throws IOException
  {
    openParen(app);
    if(_unaryOp.isPrefixOp()) {
      app.append(_unaryOp).append(_value);
    } else {
      app.append(_value).append(_unaryOp);
    }
    closeParen(app);
  }

  /**
   * Convenience method for generating a Condition for testing if a column
   * is {@code NULL}.
   * <p>
   * {@code Object} -&gt; {@code SqlObject} conversions handled by
   * {@link Converter#COLUMN_VALUE_TO_OBJ}.
   */
  public static UnaryCondition isNull(Object value) {
    return new UnaryCondition(Op.IS_NULL, value);
  }
    
  /**
   * Convenience method for generating a Condition for testing if a column
   * is not {@code NULL}.
   * <p>
   * {@code Object} -&gt; {@code SqlObject} conversions handled by
   * {@link Converter#COLUMN_VALUE_TO_OBJ}.
   */
  public static UnaryCondition isNotNull(Object value) {
    return new UnaryCondition(Op.IS_NOT_NULL, value);
  }
    
  /**
   * Convenience method for generating a Condition for testing whether a
   * subquery returns any rows.
   * <p>
   * {@code Object} -&gt; {@code SqlObject} conversions handled by
   * {@link Converter#CUSTOM_TO_SUBQUERY}.
   */
  public static UnaryCondition exists(Object query) {
    return new UnaryCondition(Op.EXISTS, query);
  }
    
  /**
   * Convenience method for generating a Condition for testing whether a
   * subquery returns exactly one row.
   * <p>
   * {@code Object} -&gt; {@code SqlObject} conversions handled by
   * {@link Converter#CUSTOM_TO_SUBQUERY}.
   */
  public static UnaryCondition unique(Object query) {
    return new UnaryCondition(Op.UNIQUE, query);
  }
    
}