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1   /*
2    * Copyright (c) 2010.  The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  
21  package org.apache.hadoop.hbase.hbql.statement.select;
22  
23  import org.apache.expreval.client.InternalErrorException;
24  import org.apache.expreval.client.NullColumnValueException;
25  import org.apache.expreval.client.ResultMissingColumnException;
26  import org.apache.expreval.expr.MultipleExpressionContext;
27  import org.apache.expreval.expr.node.GenericValue;
28  import org.apache.hadoop.hbase.hbql.client.HBqlException;
29  import org.apache.hadoop.hbase.hbql.impl.HConnectionImpl;
30  import org.apache.hadoop.hbase.hbql.mapping.MappingContext;
31  
32  public class SimpleExpressionContext extends MultipleExpressionContext {
33  
34      public SimpleExpressionContext(final GenericValue genericValue) {
35          super(null, genericValue);
36      }
37  
38      private GenericValue getGenericValue() {
39          return this.getGenericValue(0);
40      }
41  
42      public boolean isAConstant() {
43          return this.getGenericValue().isAConstant();
44      }
45  
46      public void validate() throws HBqlException {
47          this.validateTypes(this.allowColumns(), false);
48      }
49  
50      public Object getValue(final HConnectionImpl conn) throws HBqlException {
51          try {
52              this.setMappingContext(new MappingContext());
53              return this.evaluate(conn, 0, this.allowColumns(), false, conn);
54          }
55          catch (ResultMissingColumnException e) {
56              throw new InternalErrorException("Missing column: " + e.getMessage());
57          }
58          catch (NullColumnValueException e) {
59              throw new InternalErrorException("Null value: " + e.getMessage());
60          }
61      }
62  
63      public String asString() {
64          return this.getGenericValue().asString();
65      }
66  
67      public boolean useResultData() {
68          return true;
69      }
70  
71      public boolean allowColumns() {
72          return true;
73      }
74  }