Modifications in JDBC examples

diff --git a/Allgemeines/JDBC/src/main/java/de/sql/tests/RawJDBCExample.java b/Allgemeines/JDBC/src/main/java/de/sql/tests/RawJDBCExample.java
index eb8b2f5..34c3d5b 100644 (file)
--- a/Allgemeines/JDBC/src/main/java/de/sql/tests/RawJDBCExample.java
+++ b/Allgemeines/JDBC/src/main/java/de/sql/tests/RawJDBCExample.java
@@ -56,6 +56,7 @@ public class RawJDBCExample {
             logger.info("Callable statement executed successfully");          
             
         } finally {
+               // It does not implement AutoCloseable
                connection.close();
         }
     }
@@ -65,57 +66,33 @@ public class RawJDBCExample {
         * I MAY USE THE SAME Statement MORE THAN ONCE!!! :)
         */
        
-       Statement statement = null;
-       ResultSet answer = null;
-       try {
-               statement = connection.createStatement();
-               answer = statement.executeQuery("SELECT * FROM AD");
-               // Loop through ResultSet a row at a time
-               while (answer.next()) {
-                       final int adID = answer.getInt("AD_ID");
-                       final int adCode = answer.getInt("AD_CODE");
-                       final String description = answer.getString("DESCRIPTION");
-                       logger.info("AD_ID: " + adID + " AD_CODE: " + adCode + " DESCRIPTION: " + description);
-               }
-       } finally {
-               if (answer != null) {
-                // Explicitly close the cursor and connection. NOTE: IT IS NOT THE SAME AS "DECLARE CURSOR" OF SQL
-                // This is a cursor in program memory not in DBMS!!!
-                try {
-                    answer.close(); // Cursor
-                } catch (final SQLException e) {
-                    logger.error("Error while closing cursor: ", e);
-                }
-            }
-       }
-       
-       
-       try {
-               answer = statement.executeQuery("SELECT * FROM AD");
-               // Loop through ResultSet a row at a time
-               while (answer.next()) {
-                       final int adID = answer.getInt("AD_ID");
-                       final int adCode = answer.getInt("AD_CODE");
-                       final String description = answer.getString("DESCRIPTION");
-                       logger.info("AD_ID: " + adID + " AD_CODE: " + adCode + " DESCRIPTION: " + description);
-               }
-       } finally {
-               if (answer != null) {
-                // Explicitly close the cursor and connection. NOTE: IT IS NOT THE SAME AS "DECLARE CURSOR" OF SQL
-                // This is a cursor in program memory not in DBMS!!!
-                try {
-                    answer.close(); // Cursor
-                } catch (final SQLException e) {
-                    logger.error("Error while closing cursor: ", e);
-                }
-            }
-            if (statement != null) {
-                try {
-                    statement.close();
-                } catch (final SQLException e) {
-                    logger.error("Error while closing statement: ", e);
-                }
-            }
+       try (final Statement statement = connection.createStatement())
+       {
+               try (final ResultSet answer = statement.executeQuery("SELECT * FROM AD"))
+               {
+                       // Loop through ResultSet a row at a time
+                       while (answer.next()) {
+                               final int adID = answer.getInt("AD_ID");
+                               final int adCode = answer.getInt("AD_CODE");
+                               final String description = answer.getString("DESCRIPTION");
+                               logger.info("AD_ID: " + adID + " AD_CODE: " + adCode + " DESCRIPTION: " + description);
+                       }
+               }
+               // Explicitly close the cursor and connection. NOTE: IT IS NOT THE SAME AS "DECLARE CURSOR" OF SQL
+            // This is a cursor in program memory not in DBMS!!!
+               
+               try (final ResultSet answer = statement.executeQuery("SELECT * FROM AD"))
+               {
+                       // Loop through ResultSet a row at a time
+                       while (answer.next()) {
+                               final int adID = answer.getInt("AD_ID");
+                               final int adCode = answer.getInt("AD_CODE");
+                               final String description = answer.getString("DESCRIPTION");
+                               logger.info("AD_ID: " + adID + " AD_CODE: " + adCode + " DESCRIPTION: " + description);
+                       }
+               }
+               // Explicitly close the cursor and connection. NOTE: IT IS NOT THE SAME AS "DECLARE CURSOR" OF SQL
+            // This is a cursor in program memory not in DBMS!!!
        }
     }
     
@@ -124,58 +101,36 @@ public class RawJDBCExample {
         * I MAY USE THE SAME PreparedStatement MORE THAN ONCE!!! :)
         */
        
-       PreparedStatement preparedStatement = null;
-       ResultSet answer = null;
-       try {
-               preparedStatement = connection.prepareStatement("SELECT * FROM AD");
-               answer = preparedStatement.executeQuery();
-               // Loop through ResultSet a row at a time
-               while (answer.next()) {
-                       final int adID = answer.getInt("AD_ID");
-                       final int adCode = answer.getInt("AD_CODE");
-                       final String description = answer.getString("DESCRIPTION");
-                       logger.info("AD_ID: " + adID + " AD_CODE: " + adCode + " DESCRIPTION: " + description);
-               }
-       } finally {
-               if (answer != null) {
-                // Explicitly close the cursor and connection. NOTE: IT IS NOT THE SAME AS "DECLARE CURSOR" OF SQL
-                // This is a cursor in program memory not in DBMS!!!
-                try {
-                    answer.close(); // Cursor
-                } catch (final SQLException e) {
-                    logger.error("Error while closing cursor: ", e);
-                }
-            }
+       try (final PreparedStatement preparedStatement = connection.prepareStatement("SELECT * FROM AD"))
+       {
+               try (final ResultSet answer = preparedStatement.executeQuery())
+               {
+                       // Loop through ResultSet a row at a time
+                       while (answer.next()) {
+                               final int adID = answer.getInt("AD_ID");
+                               final int adCode = answer.getInt("AD_CODE");
+                               final String description = answer.getString("DESCRIPTION");
+                               logger.info("AD_ID: " + adID + " AD_CODE: " + adCode + " DESCRIPTION: " + description);
+                       }
+               }
+               // Explicitly close the cursor and connection. NOTE: IT IS NOT THE SAME AS "DECLARE CURSOR" OF SQL
+            // This is a cursor in program memory not in DBMS!!! (It is being closed by the try-catch-with-resources)
+               
+               
+               try (final ResultSet answer = preparedStatement.executeQuery())
+               {
+                       // Loop through ResultSet a row at a time
+                       while (answer.next()) {
+                               final int adID = answer.getInt("AD_ID");
+                               final int adCode = answer.getInt("AD_CODE");
+                               final String description = answer.getString("DESCRIPTION");
+                               logger.info("AD_ID: " + adID + " AD_CODE: " + adCode + " DESCRIPTION: " + description);
+                       }
+               }
+               // Explicitly close the cursor and connection. NOTE: IT IS NOT THE SAME AS "DECLARE CURSOR" OF SQL
+            // This is a cursor in program memory not in DBMS!!! (It is being closed by the try-catch-with-resources)  
        }
        
-       
-       try {
-               answer = preparedStatement.executeQuery();
-               // Loop through ResultSet a row at a time
-               while (answer.next()) {
-                       final int adID = answer.getInt("AD_ID");
-                       final int adCode = answer.getInt("AD_CODE");
-                       final String description = answer.getString("DESCRIPTION");
-                       logger.info("AD_ID: " + adID + " AD_CODE: " + adCode + " DESCRIPTION: " + description);
-               }
-       } finally {
-               if (answer != null) {
-                // Explicitly close the cursor and connection. NOTE: IT IS NOT THE SAME AS "DECLARE CURSOR" OF SQL
-                // This is a cursor in program memory not in DBMS!!!
-                try {
-                    answer.close(); // Cursor
-                } catch (final SQLException e) {
-                    logger.error("Error while closing cursor: ", e);
-                }
-            }
-            if (preparedStatement != null) {
-                try {
-                       preparedStatement.close();
-                } catch (final SQLException e) {
-                    logger.error("Error while closing statement: ", e);
-                }
-            }
-       }
     }
     
     private static void callableStatement(final Connection connection) throws SQLException {
@@ -189,19 +144,16 @@ public class RawJDBCExample {
          *    (IN OFFICE INTEGER)
          *        RETURNS VARCHAR(10)
          */
+       // Stored procedure:
+               final String str1 = "{CALL CHANGE_REGION(?, ?, ?)}";
+               // Stored function:
+               final String str2 = "{? = CALL GET_REGION(?)}";
        
-       CallableStatement cstmt1 = null;
-       CallableStatement cstmt2 = null;
-       try {
-               // Stored procedure:
-               final String str1 = "{CALL CHANGE_REGION(?, ?, ?)}";
-               // Stored function:
-               final String str2 = "{? = CALL GET_REGION(?)}";
-        
-               // Prepare the two statements
-               cstmt1 = connection.prepareCall(str1);
-               cstmt2 = connection.prepareCall(str2);
-        
+
+       try(// Prepare the two statements
+               final CallableStatement cstmt1 = connection.prepareCall(str1);
+               final CallableStatement cstmt2 = connection.prepareCall(str2))
+       {
                // Go ahead and execute the call to the stored procedure
                cstmt1.executeUpdate();
                final String adCode = cstmt1.getString("AD_CODE");
@@ -212,17 +164,6 @@ public class RawJDBCExample {
                cstmt2.registerOutParameter("AD_DESCRIPTION", Types.VARCHAR);
                // Go ahead and execute the call to the stored function
                cstmt2.executeUpdate();
-       } finally {
-            try {
-               cstmt1.close();
-            } catch (final SQLException e) {
-                logger.error("Error while closing statement: ", e);
-            }
-            try {
-               cstmt2.close();
-            } catch (final SQLException e) {
-                logger.error("Error while closing statement: ", e);
-            }
        }
     }
 }

diff --git a/Allgemeines/JDBC/src/main/java/de/sql/tests/RawJDBCLambdaExample.java b/Allgemeines/JDBC/src/main/java/de/sql/tests/RawJDBCLambdaExample.java
index a2050e0..5c5e2ab 100644 (file)
--- a/Allgemeines/JDBC/src/main/java/de/sql/tests/RawJDBCLambdaExample.java
+++ b/Allgemeines/JDBC/src/main/java/de/sql/tests/RawJDBCLambdaExample.java
@@ -69,8 +69,6 @@ public class RawJDBCLambdaExample {
         // Explicitly close the cursor and connection. NOTE: IT IS NOT THE SAME AS
         // "DECLARE CURSOR" OF SQL. This is a cursor in program memory not in DBMS!!!
         // answer.close(); // Cursor
-
-        // NOTE: in this case I do not care if we hide Exceptions while closing!!!
     }
 
     /**