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Java > Open Source Codes > org > objectstyle > cayenne > access > jdbc > SQLTemplateSelectAction


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56 package org.objectstyle.cayenne.access.jdbc;
57
58 import java.sql.Connection JavaDoc;
59 import java.sql.PreparedStatement JavaDoc;
60 import java.sql.ResultSet JavaDoc;
61 import java.sql.SQLException JavaDoc;
62 import java.util.Arrays JavaDoc;
63 import java.util.Collections JavaDoc;
64 import java.util.Iterator JavaDoc;
65 import java.util.List JavaDoc;
66 import java.util.Map JavaDoc;
67
68 import org.apache.commons.collections.IteratorUtils;
69 import org.objectstyle.cayenne.access.OperationObserver;
70 import org.objectstyle.cayenne.access.QueryLogger;
71 import org.objectstyle.cayenne.access.types.ExtendedTypeMap;
72 import org.objectstyle.cayenne.dba.DbAdapter;
73 import org.objectstyle.cayenne.query.SQLTemplate;
74
75 /**
76  * Implements a strategy for execution of selecting {@link SQLTemplate}queries.
77  *
78  * @since 1.2 replaces SQLTemplateSelectExecutionPlan.
79  * @author Andrei Adamchik
80  */
81 public class SQLTemplateSelectAction extends SQLTemplateAction {
82
83     public SQLTemplateSelectAction(SQLTemplate query, DbAdapter adapter) {
84         super(query, adapter);
85     }
86
87     /**
88      * Runs a SQLTemplate query as a select.
89      */
90     public void performAction(Connection JavaDoc connection, OperationObserver observer)
91             throws SQLException JavaDoc, Exception JavaDoc {
92
93         SQLTemplateProcessor templateProcessor = new SQLTemplateProcessor();
94         String JavaDoc template = extractTemplateString();
95         boolean loggable = QueryLogger.isLoggable(query.getLoggingLevel());
96
97         int size = query.parametersSize();
98
99         // zero size indicates a one-shot query with no parameters
100 // so fake a single entry batch...
101 Iterator JavaDoc it = (size > 0) ? query.parametersIterator() : IteratorUtils
102                 .singletonIterator(Collections.EMPTY_MAP);
103         while (it.hasNext()) {
104             Map JavaDoc nextParameters = (Map JavaDoc) it.next();
105
106             SQLSelectStatement compiled = templateProcessor
107                     .processSelectTemplate(template, nextParameters);
108
109             if (loggable) {
110                 QueryLogger.logQuery(query.getLoggingLevel(), compiled.getSql(), Arrays
111                         .asList(compiled.getBindings()));
112             }
113
114             long t1 = System.currentTimeMillis();
115
116             // TODO: we may cache prep statements for this loop, using merged string as a
117 // key since it is very likely that it will be the same for multiple parameter
118 // sets...
119 PreparedStatement JavaDoc statement = connection.prepareStatement(compiled.getSql());
120             bind(statement, compiled.getBindings());
121
122             // obtain and read ResultSet
123 ResultSet JavaDoc rs = statement.executeQuery();
124             ExtendedTypeMap types = adapter.getExtendedTypes();
125
126             RowDescriptor descriptor = (compiled.getResultColumns().length > 0)
127                     ? new RowDescriptor(compiled.getResultColumns(), types)
128                     : new RowDescriptor(rs, types);
129
130             JDBCResultIterator result = new JDBCResultIterator(
131                     connection,
132                     statement,
133                     rs,
134                     descriptor,
135                     query.getFetchLimit());
136
137             if (!observer.isIteratedResult()) {
138                 // note that we don't need to close ResultIterator
139 // since "dataRows" will do it internally
140 List JavaDoc resultRows = result.dataRows(true);
141                 QueryLogger.logSelectCount(query.getLoggingLevel(),
142                         resultRows.size(),
143                         System.currentTimeMillis() - t1);
144
145                 observer.nextDataRows(query, resultRows);
146             }
147             else {
148                 try {
149                     result.setClosingConnection(true);
150                     observer.nextDataRows(query, result);
151                 }
152                 catch (Exception JavaDoc ex) {
153                     result.close();
154                     throw ex;
155                 }
156             }
157         }
158     }
159 }
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