[CSV-123] Add possibility to use ResultSet header meta data as CSV

header apache#11.

Author: garydgregory

src/changes/changes.xml

@@ -55,7 +55,9 @@
       <action issue="CSV-149" type="fix" dev="ggregory" due-to="Kranthi, Gary Gregory, Brent Worden, dota17">Line number is not proper at EOF.</action>
       <action issue="CSV-195" type="fix" dev="ggregory" due-to="Rodolfo Duldulao, Rodolfo Duldulao, Michael Vitz, dota17">Parser iterates over the last CSV Record twice.</action>
       <action issue="CSV-267" type="fix" dev="ggregory" due-to="Arturo Bernal">Minor improvements #126, #127.</action>
-      <!-- UPDATES -->
+      <action issue="CSV-123" type="fix" dev="ggregory" due-to="Emmanuel Bourg, Benedikt Ritter, shivakrishnaah, Gary Gregory">Add possibility to use ResultSet header meta data as CSV header #11.</action>
+      <!-- ADD -->
+      <!-- UPDATE -->
       <action                 type="update" dev="ggregory" due-to="Gary Gregory">Update org.junit.jupiter:junit-jupiter from 5.6.0 to 5.7.0, #84 #109</action>
       <action                 type="update" dev="ggregory" due-to="Gary Gregory">Update tests from Apache Commons Lang 3.9 to 3.11.</action>
       <action                 type="update" dev="ggregory" due-to="Gary Gregory">Update tests from commons-io:commons-io 2.6 to 2.8.0, #108.</action>

src/main/java/org/apache/commons/csv/CSVPrinter.java

@@ -224,6 +224,18 @@ public void printComment(final String comment) throws IOException {
         println();
     }
 
+    /**
+     * Prints headers for a result set based on its metadata.
+     *
+     * @param resultSet The result set to query for metadata.
+     * @throws IOException If an I/O error occurs.
+     * @throws SQLException If a database access error occurs or this method is called on a closed result set.
+     * @since 1.9.0
+     */
+    public void printHeaders(final ResultSet resultSet) throws IOException, SQLException {
+        printRecord((Object[]) format.withHeader(resultSet).getHeader());
+    }
+
     /**
      * Outputs the record separator.
      *
@@ -388,4 +400,20 @@ public void printRecords(final ResultSet resultSet) throws SQLException, IOExcep
             println();
         }
     }
+
+    /**
+     * Prints all the objects with metadata in the given JDBC result set based on the header boolean.
+     *
+     * @param resultSet result set the values to print.
+     * @param printHeader Boolean value to print header or not.
+     * @throws IOException If an I/O error occurs
+     * @throws SQLException if a database access error occurs
+     * @since 1.9.0
+     */
+    public void printRecords(final ResultSet resultSet, final boolean printHeader) throws SQLException, IOException {
+        if (printHeader) {
+            printHeaders(resultSet);
+        }
+        printRecords(resultSet);
+    }
 }

src/test/java/org/apache/commons/csv/CSVPrinterTest.java

@@ -21,6 +21,7 @@
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
@@ -29,13 +30,13 @@
 
 import java.io.CharArrayWriter;
 import java.io.File;
+import java.io.FileReader;
 import java.io.IOException;
 import java.io.PrintStream;
+import java.io.Reader;
 import java.io.StringReader;
 import java.io.StringWriter;
 import java.io.Writer;
-import java.io.Reader;
-import java.io.FileReader;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 import java.sql.BatchUpdateException;
@@ -62,7 +63,7 @@
 import org.junit.jupiter.api.Test;
 
 /**
- *
+ * Tests {@link CSVPrinter}.
  */
 public class CSVPrinterTest {
 
@@ -86,8 +87,8 @@ private static String printable(final String s) {
     }
 
     private final String recordSeparator = CSVFormat.DEFAULT.getRecordSeparator();
-    private String longText2;
 
+    private String longText2;
     private void doOneRandom(final CSVFormat format) throws Exception {
         final Random r = new Random();
 
@@ -140,7 +141,7 @@ private <T> T[] expectNulls(final T[] original, final CSVFormat csvFormat) {
         return fixed;
     }
 
-    private Connection geH2Connection() throws SQLException, ClassNotFoundException {
+    private Connection getH2Connection() throws SQLException, ClassNotFoundException {
         Class.forName("org.h2.Driver");
         return DriverManager.getConnection("jdbc:h2:mem:my_test;", "sa", "");
     }
@@ -620,7 +621,7 @@ public void testInvalidFormat() {
     @Test
     public void testJdbcPrinter() throws IOException, ClassNotFoundException, SQLException {
         final StringWriter sw = new StringWriter();
-        try (final Connection connection = geH2Connection()) {
+        try (final Connection connection = getH2Connection()) {
             setUpTable(connection);
             try (final Statement stmt = connection.createStatement();
                     final CSVPrinter printer = new CSVPrinter(sw, CSVFormat.DEFAULT)) {
@@ -635,7 +636,7 @@ public void testJdbcPrinter() throws IOException, ClassNotFoundException, SQLExc
     public void testJdbcPrinterWithResultSet() throws IOException, ClassNotFoundException, SQLException {
         final StringWriter sw = new StringWriter();
         Class.forName("org.h2.Driver");
-        try (final Connection connection = geH2Connection()) {
+        try (final Connection connection = getH2Connection()) {
             setUpTable(connection);
             try (final Statement stmt = connection.createStatement();
                     final ResultSet resultSet = stmt.executeQuery("select ID, NAME, TEXT from TEST");
@@ -647,11 +648,32 @@ public void testJdbcPrinterWithResultSet() throws IOException, ClassNotFoundExce
                 + "\"" + recordSeparator, sw.toString());
     }
 
+    @Test
+    public void testJdbcPrinterWithResultSetHeader() throws IOException, ClassNotFoundException, SQLException {
+        final StringWriter sw = new StringWriter();
+        try (final Connection connection = getH2Connection()) {
+            setUpTable(connection);
+            try (final Statement stmt = connection.createStatement();
+                final CSVPrinter printer = new CSVPrinter(sw, CSVFormat.DEFAULT);) {
+                try (final ResultSet resultSet = stmt.executeQuery("select ID, NAME from TEST")) {
+                    printer.printRecords(resultSet, true);
+                    assertEquals("ID,NAME" + recordSeparator + "1,r1" + recordSeparator + "2,r2" + recordSeparator,
+                        sw.toString());
+                }
+                try (final ResultSet resultSet = stmt.executeQuery("select ID, NAME from TEST")) {
+                    printer.printRecords(resultSet, false);
+                    assertNotEquals("ID,NAME" + recordSeparator + "1,r1" + recordSeparator + "2,r2" + recordSeparator,
+                        sw.toString());
+                }
+            }
+        }
+    }
+
     @Test
     public void testJdbcPrinterWithResultSetMetaData() throws IOException, ClassNotFoundException, SQLException {
         final StringWriter sw = new StringWriter();
         Class.forName("org.h2.Driver");
-        try (final Connection connection = geH2Connection()) {
+        try (final Connection connection = getH2Connection()) {
             setUpTable(connection);
             try (final Statement stmt = connection.createStatement();
                     final ResultSet resultSet = stmt.executeQuery("select ID, NAME, TEXT from TEST");