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Class.forName("org.sqlite.JDBC") vs JDBC.PREFIX to load JDBC class

We had recently moved to building projects using Maven. Earlier, all the JARs were added in libs folder and added to classpath. While moving to the Maven build, I missed to add a dependency to the 'sqlite-jdbc'. This library is required to read data from a local .db3 file.
As the 'org.sqlite.JBDC' class was loaded by calling the code Class.forName("org.sqlite.JDBC"), there was no compilation error and I deployed the WAR file and servlet failed in the server. I was thinking of a way to find the issue at the compilation time itself to avoid any such mistakes in the future. Can I simply call the JDBC.PREFIX to load the JDBC, so that, If I forget to add the dependency to the pom.xml file, I can find the issue at the compile time, itself?
Is there was difference between Class.forName("org.sqlite.JDBC") vs JDBC.PREFIX to load JDBC class?

No need for Class.forName
There is no generally no need to call Class.forName.
Such calls were used in the early years. Modern Java was changed so that JDBC drivers are automatically loaded and registered with the JVM via the Java Service Provider Interface (SPI) facility.
If you are using books or tutorials advising Class.forName, you may want to obtain more up-to-date learning materials.
DataSource
Furthermore, in Servlet work you generally should not be explicitly accessing the JDBC driver.
Setting the database server address, username, and password would require hard-coding text. When the deployment sysadmins change the IP address, or rotate passwords, your code breaks. You would then have to modify your source code, re-compile, and re-deploy.
Instead, you should externalize such configuration details.
For SQLite, see Using DataSource to connect to SQLite with (Xerial) sqlite-jdbc driver.
JNDI
You can externalize database configuration by using the the DataSource interface. After obtaining a DataSource object at runtime, make database connections by calling its getConnection method. That DataSource object holds the database server address, username, password, and all other settings needed to make a connection to the database.
Obtain a DataSource object at runtime by using JNDI. Your Servlet container may act as the naming/directory server to provide the DataSource object, if your sysadmin so configures it. Or the DataSource can be obtained via JNDI from an external server such as an LDAP server.
Again, the beauty of using DataSource and JNDI is that you as the Servlet programmer need not be involved, or even informed, when the deployment details change.
JDBC driver location
For Servlet work, you generally do not bundle the JDBC driver with your app.
Instead, the JDBC driver goes into a folder managed by your Servlet container. Study the documentation for your particular Servlet container. For Apache Tomcat, see this Answer.
In development, your IDE may need access to the JDBC driver to compile. If so, in your Maven POM, mark the dependency with a <scope>provided</scope> element. This tag tells Maven to omit that dependency from the final build because the dependency will already be present (provided) at runtime.
If you insist on bundling your JDBC driver within the WAR file of your web app, then see the important Comment by Mark Rotteveel.
This topic has been addressed many times on Stack Overflow. Search to learn more.

Grails - Spring Security not working with Mysql 8

I have a application where I used these technologies:
Grails 3.3.0
JDK 1.8
Spring 4+
Mysql 8
GORM 6.1.6.RELEASE
org.grails.plugins:spring-security-core:3.2.0
Hibernate 5+
Problem is when I am trying to connect the application with Mysql 8(with 5.6+ it is working fine), I am not able to get the information related to user from Grails-Spring-Security plugin.
The application is running even connect to DB but wont be able to authenticate or fetch the information of the User like findByUsername where username is property in my user domain class.
I have User domain class defined in application.properties file.
grails.plugin.springsecurity.userLookup.userDomainClassName = 'com.aaa.User'
At some point I found this error but not sure whether it is related to this or not.
java.lang.IllegalStateException:
Either class [com.aaa.User] is not a domain class or GORM has not been initialized correctly or has already been shutdown.
Ensure GORM is loaded and configured correctly before calling any methods on a GORM entity.
Want to understand why it wont be able to fetch the information from DB. I have tried lot of things like change the GORM version to 6.1.7 and grails spring-secuirty-core plugin version but not able to get anything.
Any help would be appreciated.
Thanks,
Atul

We are able to solve the issue. It happens when grails-hibernate plugin look for the property(in my case its username as I am calling API findByUsername) which is present in the static api or not. If it is not there it throws the exception.
The thing worked for me is, I have to put the property in static mapping of User domain class:
static mapping = {
table 'userTable'
id column: 'id'
password column: 'userpassword'
username column: 'username'
}
I am not sure why it is happening, when I run the application with Mysql5.6+ its working.(The driver is according to it) but when go with Mysql8, it look for the property in static mapping.
One more point I would like to mention to fix the issue is, make sure you have tablename, columnname same as defined in DB. Case sensitivity is what expected.
As I mentioned the case sensitivity, if you are using linux with Mysql8, the lower_case_table_names=0, this check with the following as per Mysql official documentation:
Table and database names are stored on disk using the lettercase
specified in the CREATE TABLE or CREATE DATABASE statement. Name
comparisons are case sensitive. You should not set this variable to 0
if you are running MySQL on a system that has case-insensitive file
names (such as Windows or macOS). If you force this variable to 0 with
--lower-case-table-names=0 on a case-insensitive file system and access MyISAM tablenames using different lettercases, index corruption
may result.
So if the table name is static is in camel or upper case and in db it is lower case it wont match. and the error occurred.
Hope this helps to someone.

Connect to a DB2 with JDBC from domino

I am trying to connect to a db2 database from my domino application without using the extension library.
I have created a managed bean that it only connects to the db2 and prints a message on the console.
I call the method of the managed bean from a button on an xpage.
The code in the bean is this:
Class.forName("com.ibm.db2.jcc.DB2Driver");
String url = "jdbc:db2://10.0.1.49:50000/AVIN";
String user = "db2admin";
String password = "ibmdb2";
con = DriverManager.getConnection(url, user, password);
System.out.println("Successful TEST JDBC Connection!!");
I have also configured my build path and added the db2jcc.jar library.
The problem is that i am getting
java.lang.ClassNotFoundException for com.ibm.db2.jcc.DB2Driver
Why is this happening?

Is the DB2 JDBC driver available to your application? I suspect not.
You may need to package the driver in a plugin - within the NSF it will probably hit Java security issues and not work. More recent versions of the Extension Library (the Designer update site install) provide a menu option to Domino Designer to allow you to easily package up a JDBC driver as a plugin, which can then be deployed to your Update Site database.
I strongly recommend using the Extension Library. It will provide robust connection pooling amongst other things. Without it, you may well hit problems already considered and resolved by the experience of the Extension Library developers. If you do hit problems, you may struggle to find anyone with the experience to help you.

How to see all tables in my h2 database at localhost:8082?

I use JDBC and created h2 database called usaDB from sql script. Then I filled all tables with jdbc.
The problem is that after I connect to usaDB at localhost:8082 I cannot see on the left tree
my tables. There is only INFORMATION_SCHEMA database and rootUser which I specified creating usaDB.
How to view the content of tables in my h2 database?
I tried query SELECT * FROM INFORMATION_SCHEMA.TABLES.
But it returned many table names except those I created. My snapshot:

I had the same issue and the answer seems to be really stupid: when you type your database name you shouldn't add ".h2.db" suffix, for example, if you have db file "D:\somebase.h2.db" your connection string should be like "jdbc:h2:file:/D:/somebase". In other way jdbc creates new empty database file named "somebase.h2.db.h2.db" and you see what you see: only system tables.

You can use the SHOW command:
Using this command, you can lists the schemas, tables, or the columns of a table. e.g.:
SHOW TABLES

This problem drove me around the twist and besides this page I read many (many!) others until I solved it.
My Use Case was to see how a SpringBatch project created in STS using :: Spring Boot :: (v1.3.1.RELEASE) was going to behave with the H2 database; to do the latter, I needed to be able to get the H2 console running as well to query the DB results of the batch run.
This is what I did and found out:
Created an Web project in STS using Spring Boot:
Added the following to the pom.xml of the latter:
Added a Spring configuration file as follows to the project:
This solves the Web project deficiencies in STS. If you run the project now, you can access the H2 console as follows: http://localhost:8080/console
Now create a SpringBatch project in STS as follows (the alternative method creates a different template missing most of the classes for persisting data. This method creates 2 projects: one Complete, and the other an initial. Use the Complete in the following.):
The SpringBatch project created with STS uses an in memory H2 database that it CLOSES once the application run ends; once you run it, you can see this in the logging output.
So what we need is to create a new DataSource that overrides the default that ships with the project (if you are interested, just have a look at the log messages and you will see that it uses a default datasource...this is created from:
o.s.j.d.e.EmbeddedDatabaseFactory with the following parameters:
Starting embedded database: url='jdbc:hsqldb:mem:testdb', username='sa')
So, it starts an in memory, and then closes it. You have no chance of seeing the data with the H2 console; it has come and gone.
So, create a DataSource as follows:
You can of course use a properties file to map the parameters, and profiles for different DataSource instances...but I digress.
Now, make sure you set the bit that the red arrow in the picture is pointing to, to a location on your computer where a file can be persisted.
Running the SpringBatch (Complete project) you should now have a db file in that location after it runs (persisting Person data)
Run the Web project you configured previously in these steps, and you WILL :=) see your data, and all the Batch job and step run data (et voila!):
Painful but rewarding. Hope it helps you to really BOOTSTRAP :=)

I have met exactly this problem.
From what you describe, I suppose that you connect your jdbc with the "real" h2 server, but you are connecting on web application to database by the wrong mode (embedded-in-memory mode, aka h2mem). It means that h2 will create a new database in-memory, instead of using your true database stored elsewhere.
Please make sure that when you connect to this database, you use the mode Generic H2 (Server), NOTGeneric H2 (Embedded). You can refer to the picture below.

Version of jar file and installed h2 database should be same.

If in case you have created and populated H2 database table using maven dependency in spring boot, then please do change the JDBC URL as jdbc:h2:mem:testdb while connecting to H2 using web console.

It is an old question, but I came across the same problem. Eventually I found out that the default JDBC URL is pointing a test server rather than my application. After correcting it, I could access the right DB.
I tried with both Generic H2 (Embedded) and the Generic H2 (Server) options, both worked as long as the JDBC URL: is provided correctly.
In grails 4.0.1 the jdbc URL for development is jdbc:h2:mem:devDb. Check your application.yml file for the exact URL.

For the people who are using H2 in embedded(persistent mode) and want to "connect" to it from IntelliJ(other IDEs probably apply too).
Using for example jdbc url as follows: jdbc:h2:./database.h2
Note, that H2 does not allow implicit relative paths, and requires adding explicit ./
Relative paths are relative to current workdir
When you run your application, your workdir is most likely set to your project's root dir
On the other hand, IDE's workdir is most likely not your project's root
Hence, in IDE when "connecting" to your database you need to use absolute path like: jdbc:h2:/Users/me/projects/MyAwesomeProject/database.h2
For some reason IntelliJ by default also adds ;MV_STORE=false. It disables MVStore engine which in fact is currently used by default in H2.
So make sure that both your application and your IDE use the same store engine, as MVStore and PageStore have different file layouts.
Note that you cannot "connect" to your database if your application is using it because of locking. The other way around applies too.

In my case the issue was caused by the fact that I didn't set the h2 username, password in java. Unfortunatelly, Spring didn't display any errors to me, so it was not easy to figure out. Adding this lines to dataSource method helped me fix the issue:
dataSource.setUsername("sa");
dataSource.setPassword("");
Also, I should have specified the schema when creating tables in schema.sql

Selecting Generic H2 (Server) solved for me. We tempted to use default Generic H2 (Embedded) which is wrong.

Datasource creation failed using PCF User Provided Service

I have a SpringBoot application and deploying it in PCF where app is trying to connect Oracle 12c Database using PCF User Provided Services but it failing with this error Failed to determine a suitable driver class
build.gradle code:
and here are the configuration that I used in CUP service:
Service binding is happening properly. I can see the same details under VCAP_SERVICES in Environment Variables.
Error:

Short Answer: I think you want the uri to be oracle://... Strip off the jdbc: part. The Spring Autoreconfiguration code that gets injected by the Java buildpack will look at the prefix on the URI, so it needs oracle:// to know it's an Oracle link.
Long Answer: You probably don't want to depend on the injected Spring Autoreconfiguration. When it just works, it's great, but it can be difficult to understand what it's doing when it doesn't work.
It is better to use Spring Cloud Connector or even better, as all signs point to this replacing Spring Cloud Connector, use java-cfenv. For details on java-cfenv, see this blog post.
Spring Cloud Connector has the same issue I mentioned above as the Spring Autoreconfiguration, except that it will pretty clearly tell you when it doesn't recognize a bound service. Anyway, if you decide to use SCC, make sure you prefix the URI with oracle://.
If you use java-cfenv, it's more flexible so it's really up to you what properties and values you inject through the service.
Hope that helps!