I'm using a web application and, sometimes, I have MySql connection problems.
Using the testConnectionOnCheckout and preferredTestQuery options in the Hibernate configuration file, I resolved the problem and my application is ok now.
But, for better performance, I'd like to obtain the effects of this option only when a particular event occurs in my application. For example:
try {
...........
}
catch(Exception e) {
// java code to obtain the same effect as
// testConnectionOnCheckout option with "Select 1" query
}
What Java code do I have to use?
The best way to answer such a question is to look it up in the source. So I encourage you to get the source of Hibernate and find the code that tests the connection.
but anyway, here's something simple
public static boolean checkConnection(String jdbcUrl, String user, String password){
boolean result = false;
try {
Configuration config = new AnnotationConfiguration().configure();
config.setProperty("hibernate.connection.url", jdbcUrl);
config.setProperty("hibernate.connection.username", user);
config.setProperty("hibernate.connection.password", password);
sessionFactory = config.buildSessionFactory();
Session session = sessionFactory.openSession();
Assert.assertFalse(sesssion.connection.isReadOnly());
result = true;
} catch(Throwable ex) {
return = false;
}
return result;
}
Related
My Spring Boot application should connect to Filenet, which it is doing fine with the Filenet Java SDK. Now I'd like to implement a health indicator, to periodically check if the connection is still okey. Which leads me to my question:
How do I check if the connection to Filenet is successful?
What I've already tried
Creating a connection and checking if I can get the ObjectStore, which always works and never throws any error:
Connection conn = com.filenet.api.core.Factory.Connection.getConnection("https://...");
Subject subject = UserContext.createSubject(conn, "User", "password", "jaasStanzaName");
UserContext uc = UserContext.get();
uc.pushSubject(subject);
ObjectStore os = Factory.ObjectStore.getInstance(Factory.Domain.getInstance(conn, null), "objectStoreName");
Trying to do any SQL query works sort of, because it throws an EngineRuntimeException.
// Same connection as above
SearchSQL sqlObject = new SearchSQL("SELECT * FROM ...");
SearchScope searchScope = new SearchScope(conn.getObjectStore());
IndependentObjectSet results = searchScope.fetchObjects(sqlObject, null, filter, true);
But using an Exception for logic and method flows seems to me like bad code.
So are there any good methods or tried practices that I am missing?
Thanks in advance
So I eventually solved it myself, although I'm sure there are better ways to do this.
fnService is a class that essentially does what the code in the question does: creating a connection and executing an SQL query. The query doesn't really have to make much sense, even if it finds nothing it won't throw an exception. It will have to be valid SQL though.
#Component
public class FilenetHealthIndicator implements HealthIndicator {
private final FilenetService fnService;
#Autowired
public FilenetHealthIndicator(FilenetService fnService) {
this.fnService = fnService;
}
#Override
public Health health() {
log.debug("Executing automated health check Filenet");
try {
//We try to make an SQL query, if something doesn't work it will throw an EngineRuntimeException
this.fnService.searchObjectStoreWithSqlQuery("SELECT Id FROM Document WHERE Id = '{B1111111-1111-1111-AFB1-1111CD1DF11E}'");
} catch (EngineRuntimeException e){
log.error("Automated health check cannot connect to Filenet");
return Health
.down(e)
.build();
}
log.debug("Automated health check to Filenet succeeded");
return Health
.up()
.build();
}
}
I'm trying to modify existing Java app (WildFly, Jboss, oracle) which currently working fine as using persistence-unit and EntityManager connect to Oracle database(using standalone.xml and persistence.xml). However, I need to create every time new connection to database for the user which calls new GET API Endpoint using credentials from the HttpHeaders. Currently, I'm creating new entitymanager object which session is commit, rollback nad close. Unfortunately time response for every call become higher and higher. There is warning about "PersistenceUnitUser" being already registered and memory usage constantly growing. So that is bad solution.
Is there any proper way to do it, which works witout any harms ?
P.S.
Currently app using standalone.xml and persistence.xml. And that is working fine. I'm calling java api endpoint using entity manager being connected as Admin user/pass but I need to create new connection using user/pass from the httpHeaders and call one sql statement to see proper results as ORACLE uses reserved word such us: 'user'. For instance : select * from table where create_usr = user. When done 'Main EntityManager will use data from it to continue some process.
Please see code example below :
#GET
#Path("/todo-list-enriched")
#Produces(MediaType.APPLICATION_JSON)
public Response getToDoListEnriched(#Context HttpHeaders httpHeaders, #QueryParam("skip") int elementNumber, #QueryParam("take") int pageSize, #QueryParam("orderby") String orderBy)
{
String userName = httpHeaders.getHeaderString(X_USER_NAME);
String userName = httpHeaders.getHeaderString(X_PASSWORD);
EntityManager entityManager = null;
try {
Map<String, String> persistenceMap = new HashMap<String, String>();
persistenceMap.put("hibernate.dialect","org.hibernate.dialect.Oracle8iDialect");
persistenceMap.put("hibernate.connection.username", asUserName);
persistenceMap.put("hibernate.connection.password", asPassword);
EntityManagerFactory emf = Persistence.createEntityManagerFactory("PersistenceUnitUser", persistenceMap);
entityManager = emf.createEntityManager();
if (!entityManager.getTransaction().isActive()) {
entityManager.getTransaction().begin();
}
-- Do some works as select, update, select
-- and after that
if (entityManager.getTransaction().isActive()) {
entityManager.getTransaction().commit();
}
}
catch (Exception ex)
{
if (entityManager != null && entityManager.getTransaction().isActive()) {
entityManager.getTransaction().rollback();
}
}
finally {
if (entityManager != null && entityManager.isOpen()) {
entityManager.close();
}
}
}
}
``
Best Regards
Marcin
You should define a connection pool and a datasource in the standalone.xml (cf. https://docs.wildfly.org/26.1/Admin_Guide.html#DataSource) and then use it in your persistence.xml and inject the EntitytManager in your rest service class (cf. https://docs.wildfly.org/26.1/Developer_Guide.html#entity-manager).
You may look at this example application: https://github.com/wildfly/quickstart/tree/main/todo-backend
All applications using hibernate need save and update to interact with the database. For save, I will check the existence for some criteria. If it doesn't exist, I will save. For update, I will check the existence and certain criteria to determine whether update or not. What is the best practice to do the check and save / update?
I am currently creating a separate function that open a session and search to determine the existence. The session open/close is very clumsy. I think there should be better way to do it.
public Event searchByDateAddress(Date _date, String _address, boolean _closeSess)
{
try
{
if(!session.isOpen())
{
session = HibernateUtil.getSessionFactory().openSession();
}
session.beginTransaction();
Criteria criteria = session.createCriteria(Event.class);
criteria.add(Restrictions.eq("date", _date));
criteria.add(Restrictions.eq("address", _address));
criteria.setFetchMode("organizerProfile", FetchMode.JOIN);
Event evt = (Event)criteria.uniqueResult();
if(_closeSess)
{
session.close();
}
if (evt==null)
{
LogUtils.logInfo("The event does not exist: " + _date + " " + _address);
return null;
}
else
{
return evt;
}
}
catch(Exception e)
{
LogUtils.logInfo(e.toString());
if(_closeSess)
{
session.close();
}
return null;
}
}
public EventDTO insertEvent(Event _event)
{
try
{
Event tmpEvent=new Event();
//Event not exists
if((tmpEvent=this.searchByDateAddress(_event.getDate(), _event.getAddress(), true))==null)
{
//insert
if(!session.isOpen())
{
session = HibernateUtil.getSessionFactory().openSession();
}
Transaction tx=session.beginTransaction();
long retOid=(Long)session.save(_event);
session.flush();
tx.commit();
session.close();
_event.setOid(retOid);
return new EventDTO(_event);
}
}
catch(Exception e)
{
e.printStackTrace();
session.close();
}
return new EventDTO();
}
Thanks
Regarding session handling, its best to handle in the API level, a leve before this "EventService". So you always assume that the session is available in the service methods.
Then the code will look more neet, avoiding session with the hibernate query.
Its also possible to avoid session handling at all using #Transactional attribute in the methods where you want session. This is possible using Spring. Look at : https://spring.io/guides/gs/managing-transactions/ for more info.
For checking for if a table has the data you with your where clause you may use count(*). So you dont need to get all the data at first.
Look at this example: hibernate native query, count
I'm working on a webapp where i manually create my DataSource. (also see my other question why: How to use Spring to manage connection to multiple databases) because I need to connect to other databases (dev, prod, qa, test).
Now I have solved it to choose and switch between databases. But if a user logs out of my app. He wants to try to connect to an other database. He is still connected to the same datasource because at runtime the myDs is not null. How can I properly dispose of this Datasource when user logs out? I don't want the user to create the datasource every time he queries the database.
private DataSource createDataSource(Environment e) {
OracleDataSource ds = null;
String url = null;
try {
if (myDs != null) {
logger.info("myDs connection: " + etmetaDs.getConnection().getMetaData().getURL());
url = myDs.getConnection().getMetaData().getURL();
}
} catch (SQLException exc) {
// TODO Auto-generated catch block
exc.printStackTrace();
}
if (myDs == null) {
try {
ds = new OracleDataSource();
} catch (SQLException ex) {
ex.printStackTrace();
}
ds.setDriverType("oracle.jdbc.OracleDriver");
ds.setURL(e.getUrl());
try {
Cryptographer c = new Cryptographer();
ds.setUser(c.decrypt(e.getUsername()));
ds.setPassword(c.decrypt(e.getPassword()));
} catch (CryptographyException ex) {
logger.error("Failed to connect to my environment [" + e.getName() + "]");
ex.printStackTrace();
return null;
}
logger.info("Connecting to my environment [" + e.getName() + "]");
myDs = ds;
} else if (url.equals(e.getUrl())) {
} else {
}
return myDs;
}
If you read the answer of Reza in you other question you can see how to create multiple DataSource.
I think here that the problem is not the DataSource but the way you store information in your code. I suppose that your etmetaDs is shared but all your users, so dispose it when a user log out (= set it to null) is not the good option.
What you have to do, is to maintain the status of the connection for each user. And when a user log off, you can reset is status in order to obtain a new connection the next time it connects.
Update: There are many way to achieve this. I give here an example of what I imagine, but you have to adapt it to your needs. Suppose that you have a UserData object that holds information :
public class UserData
{
String id;
String name;
String database;
}
You may have in your application a dropdown with the name of the database (dev, test, ...) with an empty first item. When the user selects a database, you get the connection with createDataSource(). If it already exists you returns the DataSource else you create a new one. When your user disconnect (or when the user log on), you set the database to "" to force him to select the database in the dropdown. There is no need to reset the datasource.
I'm still working on the same problem mention here. It seems to work fine especially after creating an AbstractModel class shown below:
public abstract class AbstractModel {
protected static Connection myConnection = SingletonConnection.instance().establishConnection();
protected static Statement stmt;
protected static ResultSet rs;
protected boolean loginCheck; // if userId and userLoginHistoryId are valid - true, else false
protected boolean userLoggedIn; // if user is already logged in - true, else false
public AbstractModel (int userId, Long userLoginHistoryId){
createConnection(); // establish connection
loginCheck = false;
userLoggedIn = false;
if (userId == 0 && userLoginHistoryId == 0){ // special case for login
loginCheck = true; // 0, 0, false, false
userLoggedIn = false; // set loginCheck to true, userLogged in to false
} else {
userLoggedIn = true;
try{
String query = "select \"user_login_session_check\"(" + userId + ", " + userLoginHistoryId + ");";
System.out.println("query: " + query);
stmt = myConnection.createStatement();
rs = stmt.executeQuery(query);
while (rs.next()){
loginCheck = rs.getBoolean(1);
}
} catch (SQLException e){
System.out.println("SQL Exception: ");
e.printStackTrace();
}
}
}
// close connection
public void closeConnection(){
try{
myConnection.close();
} catch (SQLException e){
System.out.println("SQL Exception: ");
e.printStackTrace();
}
}
// establish connection
public void createConnection(){
myConnection = SingletonConnection.instance().establishConnection();
}
// login session check
public boolean expiredLoginCheck (){
if (loginCheck == false && userLoggedIn == true){
closeConnection();
return false;
} else {
return true;
}
}
}
I've already posted the stored procedures and Singleton Pattern implementation in the link to the earlier question above.
I'm under the impression that I don't need to close the connection to the database after each single data transaction, as it would just slow the application. I'm looking at about 30 users for this system I'm building, so performance and usability is important.
Is it correct to prolong the connection for at least 3-4 data transactions? Eg. Validation checks to user inputs for some form, or, something similar to google's auto-suggest ... These are all separate stored function calls based on user input. Can I use one connection instance, instead of connecting and disconnecting after each data transaction? Which is more efficient?
If my assumptions are correct (more efficient to use one connection instance) then opening and closing of the connection should be handled in the controller, which is why I created the createConnection() and closeConnection() methods.
Thanks.
Your code should never depend on the fact, that your application is currently the only client to the database or that you have only 30 users. So you should handle database connections like files, sockets and all other kinds of scarce resources that you may run ouf of.
Thus you should always clean up after yourself. No matter what you do. Open connection, do your stuff (one or SQL statements) and close connection. Always!
In your code you create your connection and save it into a static variable - this connection will last as long as your AbstractModel class lives, probably forever - this is bad. As with all similar cases put you code inside try/finally to make sure the connection gets always closed.
I have seen application servers running ouf of connections because of web applications not closing connections. Or because they closed at logout and somebody said "we will never have more then that much users at the same time" but it just scaled a little to high.
Now as you have your code running and closing the connections properly add connection pooling, like zaske said. This will remedy the performance problem of opening/closing database connection, which truely is costly. On the logical layer (your application) you doesn't want to know when to open/close physical connection, the db layer (db pool) will handle it for you.
Then you can even go and set up a single connection for your whole session model, which is also supported by DBCP - this is no danger, since you can reconfigure the pool afterwards if you need without touching your client code.
Like Tomasz said, you should never ever depend on the fact that your application will be used by a small number of clients. The fact that the driver will timeout after a certain amount of time does not guarantee you that you will have enough available connections. Picture this: a lot of databases come pre-configured with a maximum number of connections set to (say) 15 and a timeout of (let's say) 10-15 minutes. If you have 30 clients and each does an operation, somewhere around half-way you'll be stuck short on connections.
You should handle connections, files, streams and other resources the following way:
public void doSomething()
{
Connection connection = null;
Statement stmt = null;
ResultSet rs = null;
final String sql = "SELECT ....");
try
{
connection = getConnection();
stmt = connection.createStatement();
rs = stmt.executeQuery(sql);
if (rs.next())
{
// Do something here...
}
}
catch (SQLException e)
{
e.printStackTrace();
}
finally
{
closeResultSet(rs);
closeStatement(stmt);
closeConnection(connection);
}
}
The try/catch/finally guarantees you that the connection will get closed no matter the outcome. If there is some sort of failure, the finally block will still close the connection, just like it would do, if things were okay.
Similarly, with file and streams you need to do the same thing. Initialize the respective object as null outside your try/catch/finally, then follow the approach above.
This misconception makes a lot of Java applications misbehave under Windows, where people don't close files (streams to files, etc) and these files become locked, forcing you to either kill the JVM, or even restart your machine.
You can also use a connection pool such as for example Apache's DBCP, but even then you should take care of closing your resources, despite the fact that internally, the different connection pool implementations do not necessarily close the connections.
You'are right that you don't need to close the connection after each call.
Bare in mind that that modern database implement internal connection pools, but your application still need to connect and retrieve a connection object, and this is what it does now.
You should consider using a database connection pool - there are various Java frameworks to provide you such a solution, and they will define (you will be able to configure of course) when a database connection pool is closed.
In general - you should ask yourself whether your database serves only your application, or does it serve other application as well - if it does not serve other application as well, you might be able to be more "greedy" and keep connections open for a longer time.
I would also recommend that your application will create on start a fixed number of connections (define it in your configuration with a value of "Minimum connections number") and you will let it grow if needed to a maximum connection numbers.
As I previously mentioned - the ideas are suggest are implemented already by all kinds of frameworks, for example - the DBCP project of Apache.
Here is the Singleton Pattern which I initialize the myConenction field in all my Models to:
public class DatabaseConnection {
private static final String uname = "*******";
private static final String pword = "*******";
private static final String url = "*******************************";
Connection connection;
// load jdbc driver
public DatabaseConnection(){
try{
Class.forName("org.postgresql.Driver");
establishConnection();
} catch (ClassNotFoundException ce) {
System.out.println("Could not load jdbc Driver: ");
ce.printStackTrace();
}
}
public Connection establishConnection() {
// TODO Auto-generated method stub
try{
connection = DriverManager.getConnection(url, uname, pword);
} catch (SQLException e){
System.out.println("Could not connect to database: ");
e.printStackTrace();
}
return connection;
}
}
public class SingletonConnection {
private static DatabaseConnection con;
public SingletonConnection(){}
public static DatabaseConnection instance(){
assert con == null;
con = new DatabaseConnection();
return con;
}
}
Of course each and every connection to the database from the app goes through a Model.