Refactor MainController to use DataHelper and catch SQLException

src/library/assistant/database/DataHelper.java

@@ -146,4 +146,24 @@ public static MailServerInfo loadMailServerInfo() {
         }
         return null;
     }
+
+    public static ResultSet getIssueDetails(String bookID) throws SQLException {
+        return getIssueDetails(bookID, DatabaseHandler.getInstance().getConnection());
+    }
+
+    public static ResultSet getIssueDetails(String bookID, Connection conn) throws SQLException {
+        String myQuery = "SELECT ISSUE.bookID, ISSUE.memberID, ISSUE.issueTime, ISSUE.renew_count,\n"
+                + "MEMBER.name, MEMBER.mobile, MEMBER.email,\n"
+                + "BOOK.title, BOOK.author, BOOK.publisher\n"
+                + "FROM ISSUE\n"
+                + "LEFT JOIN MEMBER\n"
+                + "ON ISSUE.memberID=MEMBER.ID\n"
+                + "LEFT JOIN BOOK\n"
+                + "ON ISSUE.bookID=BOOK.ID\n"
+                + "WHERE ISSUE.bookID=?";
+        PreparedStatement stmt = conn.prepareStatement(myQuery);
+        stmt.setString(1, bookID);
+        ResultSet rs = stmt.executeQuery();
+        return rs;
+    }
 }

src/library/assistant/ui/main/MainController.java

@@ -273,17 +273,8 @@ private void loadBookInfo2(ActionEvent event) {
 
         try {
             String id = bookID.getText();
-            String myQuery = "SELECT ISSUE.bookID, ISSUE.memberID, ISSUE.issueTime, ISSUE.renew_count,\n"
-                    + "MEMBER.name, MEMBER.mobile, MEMBER.email,\n"
-                    + "BOOK.title, BOOK.author, BOOK.publisher\n"
-                    + "FROM ISSUE\n"
-                    + "LEFT JOIN MEMBER\n"
-                    + "ON ISSUE.memberID=MEMBER.ID\n"
-                    + "LEFT JOIN BOOK\n"
-                    + "ON ISSUE.bookID=BOOK.ID\n"
-                    + "WHERE ISSUE.bookID='" + id + "'";
-            ResultSet rs = databaseHandler.execQuery(myQuery);
-            if (rs.next()) {
+            ResultSet rs = DataHelper.getIssueDetails(id);
+            if (rs != null && rs.next()) {
                 memberNameHolder.setText(rs.getString("name"));
                 memberContactHolder.setText(rs.getString("mobile"));
                 memberEmailHolder.setText(rs.getString("email"));
@@ -313,8 +304,8 @@ private void loadBookInfo2(ActionEvent event) {
                 JFXButton button = new JFXButton("Okay.I'll Check");
                 AlertMaker.showMaterialDialog(rootPane, rootAnchorPane, Arrays.asList(button), "No such Book Exists in Issue Database", null);
             }
-        } catch (Exception e) {
-            e.printStackTrace();
+        } catch (SQLException e) {
+            Logger.getLogger(MainController.class.getName()).log(Level.SEVERE, null, e);
         }
 
     }

test/library/assistant/database/DataHelperTest.java

@@ -2,6 +2,7 @@
 
 import java.sql.Connection;
 import java.sql.PreparedStatement;
+import java.sql.ResultSet;
 import java.sql.SQLException;
 import library.assistant.data.model.Book;
 import org.junit.Test;
@@ -64,4 +65,37 @@ public void testInsertNewBookException() throws SQLException {
         // Assert
         assertFalse(result);
     }
+
+    @Test
+    public void testGetIssueDetails() throws SQLException {
+        // Arrange
+        Connection mockConn = mock(Connection.class);
+        PreparedStatement mockStmt = mock(PreparedStatement.class);
+        ResultSet mockRs = mock(ResultSet.class);
+        String bookID = "B100";
+
+        when(mockConn.prepareStatement(anyString())).thenReturn(mockStmt);
+        when(mockStmt.executeQuery()).thenReturn(mockRs);
+
+        // Act
+        ResultSet result = DataHelper.getIssueDetails(bookID, mockConn);
+
+        // Assert
+        assertNotNull(result);
+        assertEquals(mockRs, result);
+        verify(mockStmt).setString(1, bookID);
+        verify(mockStmt).executeQuery();
+    }
+
+    @Test(expected = SQLException.class)
+    public void testGetIssueDetailsException() throws SQLException {
+        // Arrange
+        Connection mockConn = mock(Connection.class);
+        String bookID = "B100";
+
+        when(mockConn.prepareStatement(anyString())).thenThrow(new SQLException("DB Error"));
+
+        // Act
+        DataHelper.getIssueDetails(bookID, mockConn);
+    }
 }