We Keep Coding

AssertThrows failing the test even after the right exception is thrown

#Test
void testConnectToInvalidUrl() {
model.setCredentials("cst8288", "8288");
assertThrows(SQLException.class,() -> model.connectTo("jdbc:mysql://localhost:3306/redditreader?useUnicode=true&serverTimezone=UTC&useSSL=falses"));
}
I'm trying to test this method which connects to a MySQL database in JUnit by entering a wrong url as it will throw an SQLException, which it does, but the test fails regardless. Here is the actual method:
public void connectTo(String url) {
try {
connection = DriverManager.getConnection(url, User, Pass);
} catch (SQLException e) {
e.printStackTrace();
}
}
The Exception thrown :
java.sql.SQLException: The connection property 'useSSL' only accepts values of the form: 'true', 'false', 'yes' or 'no'. The value 'falses' is not in this set.
I know its the extra s at the end, but since its a SQLException, shouldn't assertThrows make the test pass?

Does MariaDB disconnect automatically or Should i have to disconnect Manually?

I got to use MariaDB for my University Project.
it's my first time doing it, so I dont't know well how to use and code JDBC Driver and mariaDB.
Now I'm implementing the code in many places while looking at examples.
As I see, All the examples seems to creating Statement and making connection by using "DriverManager.getConnection"
Now I have a question.
I'm going to create a DBmanager Class that can connect, create tables, execute queries, and execute the code that updates data on tables in a single line.
I thought all the examples would run alone in one method and came from different places, so I could only try a new connection and create a code that would not close. But I have a gut feeling that this will be a problem.
Is there any way I can leave a connection connected at a single connection to send a command, and disconnect it to DB.disconnect()? And I'd appreciate it if you could tell me whether what I'm thinking is right or wrong.
The code below is the code I've written so far.
I am sorry if you find my English difficult to read or understand. I am Using translator, So, my English could not be display as I intended.
import java.sql.*;
import java.util.Properties;
public class DBManager {
/*********INNITIAL DEFINES********/
final static private String HOST="sumewhere.azure.com";//Azure DB URL
final static private String USER="id#somewhere";//root ID
final static private String PW="*****";//Server Password
final static private String DRIVER="org.mariadb.jdbc.Driver";//DB Driver info
private String database="user";
/***************API***************/
void setDB(String databaseinfo){
database=databaseinfo;
}
private void checkDriver() throws Exception
{
try
{
Class.forName("org.mariadb.jdbc.Driver");
}
catch (ClassNotFoundException e)
{
throw new ClassNotFoundException("MariaDB JDBC driver NOT detected in library path.", e);
}
System.out.println("MariaDB JDBC driver detected in library path.");
}
public void checkOnline(String databaseinfo) throws Exception
{
setDB(databaseinfo);
this.checkDriver();
Connection connection = null;
try
{
String url = String.format("jdbc:mariadb://%s/%s", HOST, database);
// Set connection properties.
Properties properties = new Properties();
properties.setProperty("user", USER);
properties.setProperty("password", PW);
properties.setProperty("useSSL", "true");
properties.setProperty("verifyServerCertificate", "true");
properties.setProperty("requireSSL", "false");
// get connection
connection = DriverManager.getConnection(url, properties);
}
catch (SQLException e)
{
throw new SQLException("Failed to create connection to database.", e);
}
if (connection != null)
{
System.out.println("Successfully created connection to database.");
}
else {
System.out.println("Failed to create connection to database.");
}
System.out.println("Execution finished.");
}
void makeCcnnection() throws ClassNotFoundException
{
// Check DB driver Exists
try
{
Class.forName("org.mariadb.jdbc");
}
catch (ClassNotFoundException e)
{
throw new ClassNotFoundException("MariaDB JDBC driver NOT detected in library path.", e);
}
System.out.println("MariaDB JDBC driver detected in library path.");
Connection connection = null;
}
public void updateTable(){}
public static void main(String[] args) throws Exception {
DBManager DB = new DBManager();
DB.checkOnline("DB");
}
}

For a studying project it's okay to give a connection from your DB Manager to client code and close it there automatically using try-with-resources construction.
Maybe you will find it possible to check Connection Pool tools and apply it further in your project or use as example (like HikariCP, here is a good introduction).

Read about Java try with resources. I think that this link could be usefull for your problem.
JDBC with try with resources

Best way to open and return a database connection in a Java application?

I have come up with the following utility class:
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class MySqlConnection
{
private static String dbUrl = "jdbc:mysql://localhost:3306/database";
private static String dbUsername = "root";
private static String dbPassword = "mysql";
public static Connection getConnection()
{
Connection connection = null;
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection(dbUrl, dbUsername, dbPassword);
} catch (ClassNotFoundException e) {
System.out.println("Could not load JDBC driver: " + e.getMessage());
} catch (SQLException e) {
System.out.println("Could not connect to DB: " + e.getMessage());
}
return connection;
}
}
The problem is: I do not want to return null from my method, because by doing so I force my callers to do a if (connection != null) {...} check every time they open and want to use a connection. I find these null checks to be error prone and want to avoid them at all costs. What other approach could I follow to manage database connections in my application?

First of all, as of JDBC 4.0 / Java 6, calling Class.forName() is no longer necessary. (See is Class.forName() necessary)
Next, don't bury the exceptions. Throw them up the stack, and let the callers decide how the exceptions should be handled. Depending on when getConnection() is being called you might want to:
Display an error popup box to the user
Try a different database for a connection
Run a script to try and check the status of the database and attempt to restart it if it appears to be down
Retry getConnection() completely
My point being, don't be afraid to throw Exceptions up the stack and let the caller handle the Exception appropriately.
All that being said, your getConnection() method should just need to store your DB URL, username, and password.
public class MySqlConnection
{
private static String dbUrl = "jdbc:mysql://localhost:3306/database";
private static String dbUsername = "root";
private static String dbPassword = "mysql";
public static Connection getConnection() throws SQLException
{
return DriverManager.getConnection(dbUrl, dbUsername, dbPassword);
}
}
Realistically, getConnection() will very very rarely throw an SQLException. The only scenario I've ever seen it throw an SQLException is because credentials were incorrect or the database was down.

You can throw an exception in your original code upwards, and then have to deal with a possible exception every time you would want to get a connection. Granted, you will not have null issues, but this could end up being more work. However, it does make it very explicit that you have to handle the connection not working, and this could be clearer than simply returning a null.

Refer these two questions , Should a retrieval method return 'null' or throw an exception when it can't produce the return value? and How to show if a method may return null
that should clear things a bit.
You can't avoid returning a NULL if you can't produce desired object ( In some cases, we have an option to return EMPTY objects but that is not applicable to JDBC connection object ) - All you can do is properly document your methods.
You should also avoid doing Sysouts and let the caller know about errors to expect by adding throws to your method and by re throwing exceptions. You have an option to wrap your exceptions to something more useful ( specific to your application ) before re throwing.
Also , do explicit NULL returns from your catch ( return NULL; ) instead of relying on last return statement - return connection; . There is no point of not returning immediately if not wiling to eat Exception and continue.
Lastly, you should try to use #Null and #NotNull annotations to properly document your methods.

Get data from MS Access DB using StelsMDB on Android

I'm trying to access a MS_Access db using StelsMDB library. The file is on the SD card of the phone. I loaded all libraries, created the connection:
public class DBConnection {
private static final String TAG = DBConnection.class.getSimpleName();
private Connection connection;
public DBConnection() {
try {
Class.forName(jstels.jdbc.mdb.MDBDriver2.class.getName());
connection = DriverManager.getConnection("jdbc:jstels:mdb:sdcard/2012xp.mdb");
} catch (SQLException e) {
Log.e(TAG, "", e);
} catch (ClassNotFoundException e1) {
Log.e(TAG, "", e1);
}
}
public Connection getConnection() {
return this.connection;
}
}
and it seems to work; but when i try to query something i get the following exception:
Failed parsing query
java.lang.IllegalStateException: unknown query object flag 3
Online i can't find any hint. I get this exception with a complex query, so i tryied to write an easier one like
"SELECT * FROM TABLE_NAME"
....but i get the same exception.

I belive you have a mistake in the connection string. You need to creat Connection object with it's atributes.
Try replacing your connection with this:
Connection conn = DriverManager.getConnection("jdbc:jstels:mdb:sdcard/2012xp.mdb");

After a long trying i found out that jStels is not compatible with android...

Java - Code Coverage

I have a method in one of the classes in my code base that for the life of me, I cannot get into with my junit tests.
Basically this class is called when I request a database connection, if a stale connection is returned, a new connection is established
Here is the snippet of the mthod in my class (trimmed down for this purpose)
public class TCSOracleDataSourceWrapper extends OracleDataSource {
private static final int STALE_CONNECTION_EX_CODE = 17143;
private OracleConnectionCacheManager cacheManager;
private String cacheName;
/** Local log variable **/
private final Log logger = LogFactory.getLog(getClass());
/**
* Class constructor
* #throws SQLException
*/
public TCSOracleDataSourceWrapper() throws SQLException {
super();
}
private static final long serialVersionUID = 1L;
#Override
/**
* Get a connection but if the connection is stale then refresh all DB connections
*
*/
public final Connection getConnection() throws SQLException {
logger.debug("Retrieving a database connection from the pool");
Connection connection = null;
try{
connection = super.getConnection();
}
catch(SQLException e)
{
if(e.getErrorCode() == STALE_CONNECTION_EX_CODE)
{
logger.error("Stale Oracle connection found in the Connection Pool. Refreshing invalid DB connections.");
//refresh invalid connections
cacheManager.refreshCache(cacheName, OracleConnectionCacheManager.REFRESH_INVALID_CONNECTIONS);
//now try to get the connection again
connection = super.getConnection();
}
else
{
throw e;
}
}
return connection;
}}
Any idea how I can ensure my junit tests execute the if statement?
I am currently using EasyMock and Powermock but I cannot find a way to get into this if statment using these tools
All help is greatly appreciated
Thank you
Damien

You should refactor your class to become a proxy for another data source, rather than inherit from one. This way you can easily inject into it a mock data source instead of the real one.
import javax.sql.DataSource;
public class TCSOracleDataSourceWrapper implements DataSource {
...
private DataSource wrappedDataSource;
...
public TCSOracleDataSourceWrapper(DataSource ds) {
wrappedDataSource = ds;
}
...
public final Connection getConnection() throws SQLException {
...
Connection connection = null;
try{
connection = ds.getConnection();
}
catch(SQLException e)
{
...
}
return connection;
}
}

One idea springs to mind: use aggregation rather than inheritance. This problem and others like it would go away because you can then mock the aggregated object to have whatever behavior you want. I don't see another way of getting in there right off hand. In fact, the name TCSOracleDataSourceWrapper already indicates that it's wrapping a data source (aggregation), when it actually isn't.

One quick workaround is to factor out the super.getConnection() call to a new private / protected method. Once you make that change it would be easy to mock the getBaseConnection method using power mock. This is short term fix, like the other answers suggest it is better to use delegation instead of inheritance for the wrapper implementation.
Connection getBaseConnection() throws SQLException {
return super.getConnection();
}
public final Connection getConnection() throws SQLException {
logger.debug("Retrieving a database connection from the pool");
Connection connection = null;
try{
connection = getBaseConnection();
}
catch(SQLException e)
{
if(e.getErrorCode() == STALE_CONNECTION_EX_CODE)
{
logger.error("Stale Oracle connection found in the Connection Pool. Refreshing invalid DB connections.");
//refresh invalid connections
cacheManager.refreshCache(cacheName, OracleConnectionCacheManager.REFRESH_INVALID_CONNECTIONS);
//now try to get the connection again
connection = getBaseConnection();
}
else
{
throw e;
}
}
return connection;
}