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Refactor DatabaseHandler to close Statement resources #86

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65 changes: 31 additions & 34 deletions src/library/assistant/database/DatabaseHandler.java
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,6 @@ public final class DatabaseHandler {

private static final String DB_URL = "jdbc:derby:database;create=true";
private static Connection conn = null;
private static Statement stmt = null;

static {
createConnection();
Expand Down Expand Up @@ -109,39 +108,42 @@ private static void readDBTable(Set<String> set, DatabaseMetaData dbmeta, String
}

public ResultSet execQuery(String query) {
ResultSet result;
Statement stmt = null;
ResultSet result = null;
try {
stmt = conn.createStatement();
result = stmt.executeQuery(query);
stmt.closeOnCompletion();
}
catch (SQLException ex) {
System.out.println("Exception at execQuery:dataHandler" + ex.getLocalizedMessage());
LOGGER.log(Level.ERROR, "Exception at execQuery:dataHandler {}", ex.getLocalizedMessage());
if (stmt != null) {
try {
stmt.close();
} catch (SQLException e) {
LOGGER.log(Level.ERROR, "{}", e);
}
}
return null;
}
finally {
}
return result;
}

public boolean execAction(String qu) {
try {
stmt = conn.createStatement();
try (Statement stmt = conn.createStatement()) {
stmt.execute(qu);
return true;
}
catch (SQLException ex) {
JOptionPane.showMessageDialog(null, "Error:" + ex.getMessage(), "Error Occured", JOptionPane.ERROR_MESSAGE);
System.out.println("Exception at execQuery:dataHandler" + ex.getLocalizedMessage());
LOGGER.log(Level.ERROR, "Exception at execAction:dataHandler {}", ex.getLocalizedMessage());
return false;
}
finally {
}
}

public boolean deleteBook(Book book) {
try {
String deleteStatement = "DELETE FROM BOOK WHERE ID = ?";
PreparedStatement stmt = conn.prepareStatement(deleteStatement);
String deleteStatement = "DELETE FROM BOOK WHERE ID = ?";
try (PreparedStatement stmt = conn.prepareStatement(deleteStatement)) {
stmt.setString(1, book.getId());
int res = stmt.executeUpdate();
if (res == 1) {
Expand All @@ -155,9 +157,8 @@ public boolean deleteBook(Book book) {
}

public boolean isBookAlreadyIssued(Book book) {
try {
String checkstmt = "SELECT COUNT(*) FROM ISSUE WHERE bookid=?";
PreparedStatement stmt = conn.prepareStatement(checkstmt);
String checkstmt = "SELECT COUNT(*) FROM ISSUE WHERE bookid=?";
try (PreparedStatement stmt = conn.prepareStatement(checkstmt)) {
stmt.setString(1, book.getId());
ResultSet rs = stmt.executeQuery();
if (rs.next()) {
Expand All @@ -173,9 +174,8 @@ public boolean isBookAlreadyIssued(Book book) {
}

public boolean deleteMember(MemberListController.Member member) {
try {
String deleteStatement = "DELETE FROM MEMBER WHERE id = ?";
PreparedStatement stmt = conn.prepareStatement(deleteStatement);
String deleteStatement = "DELETE FROM MEMBER WHERE id = ?";
try (PreparedStatement stmt = conn.prepareStatement(deleteStatement)) {
stmt.setString(1, member.getId());
int res = stmt.executeUpdate();
if (res == 1) {
Expand All @@ -189,9 +189,8 @@ public boolean deleteMember(MemberListController.Member member) {
}

public boolean isMemberHasAnyBooks(MemberListController.Member member) {
try {
String checkstmt = "SELECT COUNT(*) FROM ISSUE WHERE memberID=?";
PreparedStatement stmt = conn.prepareStatement(checkstmt);
String checkstmt = "SELECT COUNT(*) FROM ISSUE WHERE memberID=?";
try (PreparedStatement stmt = conn.prepareStatement(checkstmt)) {
stmt.setString(1, member.getId());
ResultSet rs = stmt.executeQuery();
if (rs.next()) {
Expand All @@ -207,9 +206,8 @@ public boolean isMemberHasAnyBooks(MemberListController.Member member) {
}

public boolean updateBook(Book book) {
try {
String update = "UPDATE BOOK SET TITLE=?, AUTHOR=?, PUBLISHER=? WHERE ID=?";
PreparedStatement stmt = conn.prepareStatement(update);
String update = "UPDATE BOOK SET TITLE=?, AUTHOR=?, PUBLISHER=? WHERE ID=?";
try (PreparedStatement stmt = conn.prepareStatement(update)) {
stmt.setString(1, book.getTitle());
stmt.setString(2, book.getAuthor());
stmt.setString(3, book.getPublisher());
Expand All @@ -224,9 +222,8 @@ public boolean updateBook(Book book) {
}

public boolean updateMember(MemberListController.Member member) {
try {
String update = "UPDATE MEMBER SET NAME=?, EMAIL=?, MOBILE=? WHERE ID=?";
PreparedStatement stmt = conn.prepareStatement(update);
String update = "UPDATE MEMBER SET NAME=?, EMAIL=?, MOBILE=? WHERE ID=?";
try (PreparedStatement stmt = conn.prepareStatement(update)) {
stmt.setString(1, member.getName());
stmt.setString(2, member.getEmail());
stmt.setString(3, member.getMobile());
Expand Down Expand Up @@ -289,13 +286,13 @@ public ObservableList<PieChart.Data> getMemberGraphStatistics() {
}

private static void createTables(List<String> tableData) throws SQLException {
Statement statement = conn.createStatement();
statement.closeOnCompletion();
for (String command : tableData) {
System.out.println(command);
statement.addBatch(command);
try (Statement statement = conn.createStatement()) {
for (String command : tableData) {
System.out.println(command);
statement.addBatch(command);
}
statement.executeBatch();
}
statement.executeBatch();
}

public Connection getConnection() {
Expand Down
78 changes: 78 additions & 0 deletions test/library/assistant/database/DatabaseHandlerTest.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,78 @@
package library.assistant.database;

import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mock;
import org.mockito.junit.MockitoJUnitRunner;

import static org.mockito.ArgumentMatchers.anyString;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;

@RunWith(MockitoJUnitRunner.class)
public class DatabaseHandlerTest {

@Mock
private Connection mockConnection;

@Mock
private Statement mockStatement;

@Mock
private ResultSet mockResultSet;

@Test
public void testExecQueryClosesStatementOnCompletion() throws Exception {
// Setup mock behavior
when(mockConnection.createStatement()).thenReturn(mockStatement);
when(mockStatement.executeQuery(anyString())).thenReturn(mockResultSet);

// Get instance (it's a singleton)
// This will trigger static initialization. Ensure libs are in classpath.
DatabaseHandler handler = DatabaseHandler.getInstance();

// Inject mock connection via reflection
Field connField = DatabaseHandler.class.getDeclaredField("conn");
connField.setAccessible(true);
connField.set(null, mockConnection); // static field

// Execute query
ResultSet rs = handler.execQuery("SELECT * FROM TEST");

// Verify statement creation and execution
verify(mockConnection).createStatement();
verify(mockStatement).executeQuery("SELECT * FROM TEST");

// Verify closeOnCompletion is called
verify(mockStatement).closeOnCompletion();
}

@Test
public void testExecActionClosesStatement() throws Exception {
// Setup mock behavior
when(mockConnection.createStatement()).thenReturn(mockStatement);
when(mockStatement.execute(anyString())).thenReturn(true);

// Get instance
DatabaseHandler handler = DatabaseHandler.getInstance();

// Inject mock connection via reflection
Field connField = DatabaseHandler.class.getDeclaredField("conn");
connField.setAccessible(true);
connField.set(null, mockConnection);

// Execute action
handler.execAction("UPDATE TEST SET A=1");

// Verify statement creation and execution
verify(mockConnection).createStatement();
verify(mockStatement).execute("UPDATE TEST SET A=1");

// Verify close is called
verify(mockStatement).close();
}
}