There are 2 ways to connect to a database when developing Java apps.
Using DriverManager
Connection conn = DriverManager.getConnection(url, name, password);
// execute the query.
Using application property file in SpringBoot
spring.jpa.hibernate.ddl-auto=none
spring.datasource.url=jdbc:mysql://localhost:5432/db_name
spring.datasource.username=user
spring.datasource.password=password
Now you can use #Entity annotation on your class to put data into database.
My question is how are these 2 ways different. If not how, is SpringBoot method working same as DriverManager in the background.
I assume that by Driver Manager you wanted to made reference to JDBC and by Springboot(Hibernate) you wanted to say JPA.
To simply answer your question, both JDBC and JPA will connect to the driver. Just that if you use JPA this step is made by default without you explicitly coding it.
You can look at JPA as an upper layer of JDBC which handles all the boilerplate code like connecting to the driver.
You can read more about JPA and JDBC here: JPA or JDBC, how are they different?
When you set configuration properties you are just saying to spring: "Hey, i have this properties, can you autoconfigure what i need?". At this point spring at the start of application will use you configuration properties to setup everything you need to connect to your database (using DriverManager or not is not important).
Spring do exactly what you should to do to configure your database connection.
Remember that in 99% of cases you can't write better code than spring do. So, use spring properties
Related
I was asked this question by a colleague, and I am unable to answer it:
I have an in memory database (h2), and I have a SQL database server which our app needs to talk too. But due to the two different SQL dialects we are now wondering how do we get around the issue by doing the least amount of work?
This to be done in spring boot. I am aware of how to connect to the h2 database and SQL database server, but I am unsure on the rest.
If everything is setup by Spring, you should not be worried about the 2 different SQL dialects. Just be sure that spring.jpa.database is set to default to let Spring autodetect the right dialect for each datasource.
Here's a link that explain how to use/initialize two datasource in a Spring Boot projet if you need some more information.
I created a small POC app with spring boot, using hibernate (5.2.9) and maria db (10.1.19).
I had some sql dialect issues where my create/drop table SQL was using type=MyIasam but resolved that locally by setting the spring.jpa.properties.hibernate.dialect, however, when I deploy to the cloud (PCF) all of the cloud profile stuff kicks in, and I end up with hibernate deciding its dialect is going to be org.hibernate.dialect.MySQLDialect
this results in invalid SQL getting generated for creating new tables.
Note that I'm not really sure what else could be happening. This is a spring boot app (1.5.3) and the cloud profile is kicking in to do auto configuration. There's a bunch of properties injected. And I can't seem to get my dialect property to be respected.
This is a solid crushingly easy problem that is the escaping me.
Any ideas what I need to set, or provide as dependencies?
I tried removing all of the mysql dependencies, but then the connection string inject is jdbc:mysql... which i think may be part of the problem...
I have a simple spring boot application. I am using JDBC connection configured by JDBC Template (JDBC url is got from properties file).
Can you tell me how to reach following thing:
JDBC Connection should be established in depends on logged user, I have a problem with projecting in spring such flow of control that object jdbc template will be created after loggining user.
It is about different users use different database.
Can you help me, please?
You can do the routing at the datasource level.
See https://spring.io/blog/2007/01/23/dynamic-datasource-routing/
And
http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/jdbc/datasource/lookup/AbstractRoutingDataSource.html
How can i configure default data source of j boss for data base connection and database fail over. How can i get connection to my java class from that data source. Am using hibernate and my database in Mysql.
I think you should find everything you need at this documentation for datasources
I am about to make a connection to my database and I am using EJB and JPA. I have recently started doing these technologies so I have some problems understand it all at this point:)
I know that the persistence.xml is needed in order to use JPA. It is the file where I configure how to connect to the database, that I know. However it seems like there are multiple ways of doing it.
What would be the difference (or when should I even use the one alternative over the other?) of defining properties such as username, database, password etc. in the persistence.xml file and in Glassfish? Advantages/disadvantages if any.
Underneath on the image I posted I have JDBC Resources and JDBC Connection Pools. I am a litte confused about the terminology of the two. Why don't we add properties such as username, database, password and so on in the JDBC Resources? Could someone explain the difference between them and what they mean?
JDBC Resources
A JDBC resource (data source) provides applications with a means of
connecting to a database. Typically, the administrator creates a JDBC
resource for each database accessed by the applications deployed in a
domain. (However, more than one JDBC resource can be created for a
database.)
http://download.oracle.com/docs/cd/E19316-01/820-4335/ablih/index.html
I think it strange that we add such properties on the pool but not in the resource, but I probably misunderstand the concepts.
In the "JDBC connection pools" you can create container managed JDBC data sources (with connection pooling capabilities). The data source needs to know about at least the JDBC driver, the JDBC URL, username and password.
In the "JDBC resources" you can bind those container managed JDBC data sources to one or more JNDI names so that they are by JNDI available to the deployed web application.
In the persistence.xml you can specify whether to use a local data source or to use a container managed data source. If you want to use a container managed data source, then you should specify its JNDI name. Using a container managed data source has the advantage that you can share a single data source among multiple web applications. In case of JPA, it has also the advantage that you can make use of JTA (container managed transactions) so that you don't need to call transaction.begin(), commit(), rollback() etc in every method.