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ebean core module
There is a newer version: 15.8.0
package io.ebeaninternal.server.expression;

import io.ebean.util.SplitName;
import io.ebeaninternal.api.*;
import io.ebeaninternal.server.deploy.BeanDescriptor;
import io.ebeaninternal.server.el.ElPropertyValue;

import java.io.IOException;


/**
 * Null / Not Null expression.
 * 
 * Note that for OneToMany/ManyToMany this effectively gets translated into isEmpty()/isNotEmpty().
 * 
 */
final class NullExpression extends AbstractExpression {

  private final boolean notNull;
  private ElPropertyValue elProperty;
  private boolean assocMany;
  private String propertyPath;

  NullExpression(String propertyName, boolean notNull) {
    super(propertyName);
    this.notNull = notNull;
  }

  @Override
  public void containsMany(BeanDescriptor desc, ManyWhereJoins manyWhereJoin) {
    elProperty = desc.elGetValue(propName);
    if (elProperty != null && elProperty.isAssocMany()) {
      // it is OneToMany or ManyToMany so going to be treated as isEmpty() expression
      assocMany = true;
      propertyPath = SplitName.split(propName)[0];
      propertyContainsMany(propertyPath, desc, manyWhereJoin);
    } else {
      if (elProperty != null && elProperty.containsMany() && !notNull) {
        manyWhereJoin.setRequireOuterJoins(true);
      }
      propertyContainsMany(propName, desc, manyWhereJoin);
    }
  }

  @Override
  public void writeDocQuery(DocQueryContext context) throws IOException {
    context.writeExists(notNull, propName);
  }

  @Override
  public void addBindValues(SpiExpressionBind request) {

  }

  @Override
  public void addSql(SpiExpressionRequest request) {
    if (assocMany) {
      // translate to exists sub-query
      IsEmptyExpression.isEmptySql(request, elProperty, !notNull, propertyPath);
      return;
    }
    String nullExpr = notNull ? " is not null" : " is null";
    if (elProperty != null && elProperty.isAssocId()) {
      request.parse(elProperty.assocIdExpression(propName, nullExpr));
    } else {
      request.property(propName).append(nullExpr);
    }
  }

  @Override
  public boolean isSameByBind(SpiExpression other) {
    // no bind values so always true
    return true;
  }

  /**
   * Based on notNull flag and the propertyName.
   */
  @Override
  public void queryPlanHash(StringBuilder builder) {
    if (notNull) {
      builder.append("NotNull[");
    } else {
      builder.append("Null[");
    }
    builder.append(propName).append(']');
  }

  @Override
  public void queryBindKey(BindValuesKey key) {
    key.add(notNull);
  }
}