I am trying to unit test a thin data access layer that I've written. I was hoping I wouldn't have to inject a stub of DriverManager into the class that makes the connection, and I don't have a mock framework available. I have check my implementation against MockRunner's MockDriver and it is very similar, but when I run the test I get a SQLException: "No suitable driver found for jdbc:mysql://localhost:3306." Here is the stub code:
public class DriverStub implements Driver
{
#Override
public boolean acceptsURL(String URL) throws SQLException
{
return true;
}
#Override
public Connection connect(String url, Properties info) throws SQLException
{
return new ConnectionStub();
}
#Override
public int getMajorVersion()
{
return 1;
}
#Override
public int getMinorVersion()
{
return 0;
}
#Override
public DriverPropertyInfo[] getPropertyInfo(String url, Properties info)
throws SQLException
{
return new DriverPropertyInfo[0];
}
#Override
public boolean jdbcCompliant()
{
return true;
}
}
A fragment of the calling code:
Connection connection = null;
try
{
Class.forName(driver).newInstance();
}
...
try
{
connection = Drivermanager.getConnection(...);
}
...
The Driver implementation should register an instance of the Driver through DriverManager.registerDriver in its static initialiser.
public class DriverStub implements Driver {
static {
java.sql.DriverManager.registerDriver(new DriverStub());
}
...
}
It's a complete and utter hack, but there you go. Personally, I'd suggest ignoring DriverManager and linking directly to the driver.
This seems to be far more effort than it's worth. Why would you want to stub the DriverManager? What does that test? How do you prove the worth of your data access layer by not using a real driver manager? Don't you want to connect to a database to test?
I'd load the JDBC driver and be done with it. This seems like mocking run amok to me.
Related
I'm trying to create a database connection library to be used in all my apps. I want to make sure that this library is fully unit tested and so i'm trying to use dependency injection.
I have this class which i want to ensure is tested:
public class ConnectionFactory {
private String dataSourceName;
public ConnectionFactory(String dataSourceName) {
if(dataSourceName == null) {
throw new NullPointerException("dataSourceName can't be null");
}
this.dataSourceName = dataSourceName;
}
public Connection getConnection() throws SQLException {
Connection connection = getDataSource(dataSourceName).getConnection();
if(connection != null) {
return connection;
}
...
}
// Get a datasource object
private DataSource getDataSource(String dataSourceName) {
...
try {
Context ctx = new InitialContext();
dataSource = (DataSource) ctx.lookup("java:comp/env/" + dataSourceName);
} catch (NamingException e) {
...
}
return dataSource;
}
}
I want to be able to simply call this class from all my apps with something as simple as this:
public class MyApp {
public static void main(string[] args) {
ConnectionFactory connectionFactory = new ConnectionFactory("jdbc/myDataSource");
Connection connection = connectionFactory.getConnection();
}
}
I've started writing unit tests for this ConnectionFactory, but quickly realized that with my current code I can't mock the DataSource object so it's trying to actually connect to a real data source.
#RunWith(Nested.class)
public class ConnectionFactoryTest {
public class Constructor {
#Test
public void shouldThrowNullPointerIfParamIsNull() {
assertThatExceptionOfType(NullPointerException.class)
.isThrownBy(() -> { new ConnectionFactory(null); })
.withMessage("dataSourceName can't be null");
}
}
public class GetConnection {
public class WithDataSourceAvailable {
#Test
public void shouldErrorIfParamIsNull() {
ConnectionFactory connectionFactory = new ConnectionFactory("jdbc/myDataSource"); // <-- This is going to fail b/c it's trying to actually fetch a real data source
}
}
}
}
How can I properly use Dependency Injection so that I can write unit tests that don't actually try to connect to a data source?
Take a look at Mockito I find it easy to use for this type of mocking.
I have a db design issue that I am facing with one of my projects. I am trying to implement a service and part of that service is a db layer. It is setup such that I have helper classes that perform get/update methods to the database and a layer on top of them that is a janitor. For ex:
public class GetStudentDBHelper {
public List<Student> get(List<Integer> ids) {
Conn getConnection...
// run sql query and construct returning Student objects
}
public List<Student> get(List<Classroom> byClassroom) {
// get all students in passed in classrooms
// run sql query and construct returning Student objects
}
}
public class StudentJanitor {
public GetStudentDBHelper getStudentDBHelper;
public UpdateStudentDBHelper updateStudentDBHelper;
public UpdateClassroomDBHelper updateClassroomDBHelper;
public List<Student> getStudents(List<Integer> ids) {
return getStudentDBHelper.get(ids);
}
public void saveStudents(List<Students> students, int classRoomid) {
Connection conn = Pool.getConnection(); // assume this gives a jdbc
conn.autocommit(false);
try {
try
{
updateStudentDBHelper.saveForClassroom(students, classRoomid, conn);
updateClassroomDBHelper.markUpdated(classRoomid, conn);
conn.commit();
}
catch
{
throw new MyCustomException(ErrorCode.Student);
}
}
catch (SQLException c)
{
conn.rollback();
}
finally {
conn.close();
}
}
public class ClassroomJanitor{
public void saveClassRoon(List<Classrooms> classrooms) {
Connection conn = Pool.getConnection()// assume this gives a jdbc
conn.autocommit(false);
try {
try {
updateClassroomDBHelper.save(classrooms, conn);
updateStudentDBHelper.save(classrooms.stream().map(Classroom::getStudents).collect(Collections.toList()), conn);
conn.commit();
}
catch {
throw new MyCustomException(ErrorCode.ClassRoom);
}
}
catch (SQLException c)
{
conn.rollback();
}
finally {
conn.close();
}
}...
public class GetClassroomDBHelper{}...
public class UpdateClassroomDBHelper{}...
The update db classes all compose multiple other updators in case they need to update values in other tables (ie. saving a student means I have to touch a classroom table in which a student belongs to update its last updated time for instance).
The issue I am having is for the update db classes, I have to pass in a connection from my Janitor class if i am touching multiple tables in order to have transactions and their rollback capabilities. See above for what I mean. Is there a better way to do this? This type of try, catch, pass in conn to db helpers, will have to be done for any multi transaction operation in my janitors.
In short, you can see that the code is generally like this duplicated across multiple methods:
Connection conn = Pool.getConnection()// assume this gives a jdbc
conn.autocommit(false);
try {
try {
//do some business logic requiring Connection conn
}
catch {
throw new MyCustomException(ErrorCode);
}
}
catch (SQLException c)
{
conn.rollback();
}
finally {
conn.close();
}
Whenever you have a code sequence that is duplicated but it only differs in some parts you can use a template method.
In your case I would introduce a TransactionTemplate class and use a callback interface for the parts that are different. E.g.
public class TransactionTemplate {
private DataSource dataSource;
public TransactionTemplate(DataSource dataSource) {
this.dataSource = Objects.requireNonNull(dataSource);
}
public <T> T execute(TransactionCallback<T> transactionCallback) throws Exception {
Connection conn = dataSource.getConnection();// assume this gives a jdbc
try {
conn.setAutoCommit(false);
T result = transactionCallback.doInTransaction(conn);
conn.commit();
return result;
} catch (Exception e) {
conn.rollback();
throw e;
} finally {
conn.close();
}
}
}
The callback interface would look like this
public interface TransactionCallback<T> {
public T doInTransaction(Connection conn) throws Exception;
}
As you can see the TransactionTemplate manages the transaction while the TransactionCallback implements the logic that must be done in one transaction.
Your client code will then look like this
public class StudentJanitor {
private TransactionTemplate transactionTemplate;
StudentJanitor(DataSource dataSource) {
transactionTemplate = new TransactionTemplate(dataSource);
}
public void saveStudents(List<Students> students, int classRoomid) {
SaveStudentsTransaction saveStudentsTransaction = new SaveStudentsTransaction(students, classRoomid);
transactionTemplate.execute(saveStudentsTransaction);
}
}
and the logic is placed in the TransactionCallback
public class SaveStudentsTransaction implements TransactionCallback<Void> {
public GetStudentDBHelper getStudentDBHelper;
public UpdateStudentDBHelper updateStudentDBHelper;
public UpdateClassroomDBHelper updateClassroomDBHelper;
private List<Students> students;
private int classRoomid;
public SaveStudentsTransaction(List<Students> students, int classRoomid) {
this.students = students;
this.classRoomid = classRoomid;
}
#Override
public Void doInTransaction(Connection conn) throws Exception {
try
{
updateStudentDBHelper.saveForClassroom(students, classRoomid, conn);
updateClassroomDBHelper.markUpdated(classRoomid, conn);
conn.commit();
}
catch
{
throw new MyCustomException(ErrorCode.Student);
}
return null;
}
}
Two main concerns you are currently facing are the boiler plate code for repetitive tasks related to connection (get/execute/close etc)
and infrastructure for getting the same connection across method boundaries. The first is typically solved using Template pattern and the latter
using Threadlocal variables to pass around appropriate connection across methods. These type of concerns have been solved in Java world long ago but
will require you to rely on framework like Spring (JDBC template) etc which have this feature from last decade or so or you would need to roll out stripped
down version of this infrastructure. If you are interested in latter then you can take hint from similar attmepts shared on Github like this.
I've created a Rest service with four methods, GET,POST,UPDATE and DELETE.
These methods make connections to a Database to retrieve and store data.
Now I want to test each method. I've used the Jersey Test Framework for this. And it is working as long as I remove the code what actually makes the call to the database. When I leave the code that makes the call to the database it throws an exception that it could not connect to the database.
EDIT: I have done some research and used dependancy injection. The db calls are moved to a separate class but I'm still doing something wrong.
DatabaseResults. In this class the call to the DB is made.
public class DatabaseResults {
private final String getQuery = "SELECT * FROM movies";
private Connection connection = null;
private PreparedStatement pstmt = null;
private final ArrayList<Movie> jsonList = new ArrayList<>();
public JSONObject getAllMovies() throws SQLException {
try {
ComboPooledDataSource dataSource = DatabaseUtility.getDataSource();
connection = dataSource.getConnection();
pstmt = connection.prepareStatement(getQuery);
ResultSet rs = pstmt.executeQuery();
while (rs.next()) {
jsonList.add(new Movie(rs.getString(1), rs.getString(2), rs.getString(4), rs.getString(3)));
}
} catch (SQLException ex) {
System.out.println(ex);
System.out.println("Could not retrieve a connection");
connection.rollback();
} finally {
connection.close();
}
JSONObject jsonObject = new JSONObject();
jsonObject.put("movies", jsonList);
return jsonObject;
}
}
MoviesResource that contains the REST methods
#Path("movies")
public class MoviesResource {
....
private DatabaseResults dbResults = null;
public MoviesResource() {
this(new DatabaseResults());
}
MoviesResource(DatabaseResults dbr){
this.dbResults = dbr;
}
....
#GET
#Produces(MediaType.APPLICATION_JSON)
public Response getAllMovies() throws JSONException, SQLException {
return Response.status(200).entity(dbResults.getAllMovies().toString()).build();
}
The Test class
#RunWith(MockitoJUnit44Runner.class)
public class MovieResourceTest extends JerseyTest {
JSONObject jsonObject = new JSONObject();
#Mock
DatabaseResults dbr;
#Before
public void setup() throws SQLException{
jsonObject.put("id", "hello");
when(dbr.getAllMovies()).thenReturn(jsonObject);
}
Client client = ClientBuilder.newClient();
WebTarget target = client
.target("http://localhost:9998/RestServiceMovies/resources");
#Override
protected Application configure() {
return new ResourceConfig(MoviesResource.class);
}
#Test
public void getAllMoviesTest() throws SQLException {
String responseGetAllMovies = target("/movies").request().get(String.class);
Assert.assertTrue("hello".equals(responseGetAllMovies));
}
At this moment I can run the tests but still when I test the getAllMovies() method it makes a call to the real database instead of returning the jsonObject.
I have the feeling that a connection is missing between the mock object and the constructor from the MovieResource class?
When you register your resource as a class
new ResourceConfig(MoviesResource.class)
you are telling Jersey to create the instance. If you don't have any DI configured, it will just call the no-arg constructor. In your no-arg constructor, you are just creating the service yourself. It knows nothing about your mock.
What you should do instead is register the resource class as an instance. That way you can pass the mock to the constructor.
MockitoAnnotations.initMocks(this);
return new ResourceConfig()
.register(new MoviesResource(dbr));
Don't use the Mockito runner. Instead use the MockitoAnnotations.initMocks method. That way you control when the #Mocks are injected. If you use the runner, the injection will not happen in time, as the the configure method is called by the framework before the Mockito injection happens.
I've implemented an RMI interface with these current files;
MyClient.java - Clientside code
MyServer.java - Serverside code
Adder.java - Interface
AdderRemote.java - Remote _implements Adder_
DataAccess.java - Contains all the methods to interveen between server and client
I have a vps which contains all files except the Client file in the directory
vps:~/rmi#
When testing this on it's own, ie: compiling on the server, doing
rmic AdderRemote
rmiregistry 5000&
(the port I have chosen)
java -classpath .:mysql-connector... MyServer
and then locally doing the same process but running the MyClient java instead, it works. The problem I am facing is now implementing this into a project I have running in eclipse as a part of this;
I have an instance of MyClient in the main file which is then passed as parameters to the certain classes (This project implements the MVC pattern and is passed to fellow model class'), and I am now getting the error
java.rmi.NotBoundException: xox
after googling, the only response I could find was "Attempt to look up a name that is not bound.", But I'm not really sure what this means? I'll attach my code, and any help would be much appreciated.
MyClient.java
public class MyClient
{
public Adder stub;
public MyClient ()
{
try
{
stub = (Adder)Naming.lookup("rmi://92.222.2.96:5000/xox");
}
catch (Exception e)
{
System.out.println(e.toString());
}
}
public static void connect(Adder stub) throws RemoteException
{
System.out.println(stub.connect());
}
Adder.java
public interface Adder extends Remote
{
public String connect() throws RemoteException;
}
AdderRemote.java
public class AdderRemote extends UnicastRemoteObject implements Adder
{
public AdderRemote() throws RemoteException
{
super();
da = new DataAccess();
}
DataAccess da;
public String connect() throws RemoteException
{
return da.connect();
}
DataAccess.java
public class DataAccess
{
// Connection info
static final String URL = "jdbc:mysql://92.222.2.96:3306/groupproj";
static final String DRIVER = "com.mysql.jdbc.Driver";
static final String USERNAME = "root";
static final String PASSWORD = "*****";
Connection c = null;
public String connect()
{
try
{
Class.forName(DRIVER).newInstance(); //Load DB driver
c = DriverManager.getConnection(URL, USERNAME, PASSWORD); //Establish connection to DB2
return "Connected.";
}
catch(Exception e)
{
return e.toString();
}
}
MyServer.java
public class MyServer
{
public static void main ( String args[] )
{
try
{
Adder stub = new AdderRemote();
Naming.rebind("rmi://92.222.2.96:5000/xox", stub);
}
catch ( Exception e )
{
System.out.println(e);
}
}
public static void connect(Adder stub) throws RemoteException
{
try
{
stub.connect();
}
catch(Exception e)
{
System.out.println("Could not connect to the DB.");
}
}
I gathered that because the files on the server are located in the directory "rmi" I renamed the xox to this, but this did not solve the problem, so I reverted it back to xox, which it worked before putting it into a java project.
Thank you
You must have got an exception doing the bind.
If you got a NotBoundException when looking up the same name in the same Registry you're supposed to have bound it to, you didn't bind it at all.
Notes:
You can only bind to a Registry that is running in the same host as yourself. For that reason it is convenient to always use "localhost" as the hostname when calling bind(), rebind(), or unbind().
You'd be better off letting the RemoteException and NotBoundException be thrown from the constructor of MyClient.
MyClient.connect() should not be static. In fact it cannot be static. Ergo this cannot be the real code.
From what we can see so far, your system isn't correctly designed. Your server should get a DBMS connection when it needs one, inside a remote method, on behalf of the client that is calling that method, and release it before exiting the method. Opening a new connection every time a client asks for one explicity and storing it into an instance variable of the remote object (a) will leak connections and (b) won't work when concurrent clients come to execute a query or update on the same connection.
I am developing an application that needs to store information to a database. I would like to use a Scala solution if possible. If the database connectivity fails for some reason, I would like to write the raw SQL statements that would have been executed to a .sql script file. The idea is that when/if the connectivity to the database is restored I would like to execute that script in Scala/Java to bring the database back into sync. It is also nice to have the .sql script around in case there is a failure in the program, so that a manual execution of the script could occur.
How do I record the sql statements that I am going to execute to a file in Scala/Java? Then, how do I execute a that file (or really any .sql script) in Scala/Java?
you can proxy your Connection object:
public class ConnectionProxy {
public ConnectionProxy(Object anObject) {
super(anObject);
}
#Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
Object result = method.invoke(target, args);
String methodName = method.getName();
if (methodName.equals("createStatement")) {
result = ProxyBuilder.createProxy(result, new StatementProxy(result));
}
return result;
}
}
in order to intercept any call to Statement.execute(String sql):
public class StatementProxy {
public StatementProxy(Object anObject) {
super(anObject);
}
#Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
try {
return method.invoke(proxy, args);
} catch (SQLException sqle) {
if (method.getName().contains("execute")) {
String sql = "";
if (args != null && args[0] != null) {
sql = args[0].toString();
}
saveToFile(arg);
}
throw sqle;
}
}
}
where ProxyBuilder is a simple helper class:
public final class ProxyBuilder {
public static Connection tracingConnection(Connection connection) {
return createProxy(connection, new ConnectionProxy(connection));
}
static <T> T createProxy(T anObject, InvocationHandler invocationHandler) {
return createProxy(anObject, invocationHandler, anObject.getClass().getInterfaces());
}
static <T> T createProxy(T anObject, InvocationHandler invocationHandler, Class... forcedInterfaces) {
return (T) Proxy.newProxyInstance(
anObject.getClass().getClassLoader(),
forcedInterfaces,
invocationHandler);
}
}
Of course, this is not your final production code but it is a good starting point.