How to create database tables from JPA using Hibernate
We know ORM. It will be a nightmare or a bliss based on the angle you are looking at it. This time a bliss
If you have started development from the java side and you have all the entities figured out, then hibernate can create the database for you from the entities.
For this example I will be assuming you are using Spring and Hibernate, with that, how do you create the database from the entities
Initial Setup assumptions
So, I will be assuming you have the spring being setup already, the configuration file for your application would look like:
jdbc.driverClassName = com.mysql.jdbc.Driver
jdbc.url = jdbc:mysql://localhost:3306/database
jdbc.username = root
jdbc.password = 123
hibernate.dialect = org.hibernate.dialect.MySQLDialect
hibernate.show_sql = true
hibernate.format_sql = true
hibernate.hbm2ddl.auto = create|create-drop|update|none
Here the values to
hibernate.hbm2ddl.auto could be create – if you want to crate during the sessionFactory initiation, create-drop, update when you want to update the exiting database when there is a change on the schema or none if you don’t want to do anything with it.
When working on spring framework, you might get this error specially on eclipse. I am assuming you are working on maven and eclipse environment.
ClassNotFound exception is a bit self explanatory that eclipse could not find the mentioned class
web.xml file for the spring configuration might look like
With this, you might have similar file like
application-context in the WEB-INF path
How to fix ClassNotFoundException for ContextLoaderList
The problem will during deployment. It is not basically compile time error. It is rather runtime error.
So, we have to make sure the jar responsible for this class is available in the classpath that eclipse is reading.
Pom dependency check
Make sure you have the same/similar configuration as the one listed below on your pom file.
You can have the right version for your spring in the parameter section or you can just replace it with the current version you have.
Using Deployment Assembly fix in eclipse
As we know, it is a deployment time problem, hence we have to tell the assembly where it can get its dependencies.
Right click on the project
Go to/search for Deployment Assembly
Click on Add
Select on Java Build path entries
Select all the maven dependencies
Clean and build the project
Either of the above methods should fix the problem
Spring data with spring boot error when using mapping
Spring boot has made life of the java developers a bliss. Thanks a million for the dedicated guys in spring.
Saying that, if you are working typical database related project with spring boot, you might have some error like this
java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.catalina.connector.Response.getWriter(Response.java:624) ~[tomcat-embed-core-8.5.16.jar!/:8.5.16]
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:211) ~[tomcat-embed-core-8.5.16.jar!/:8.5.16]
Continue reading Spring Data error: getOutputStream() has already been called for this response