Tutorial Starting and Using the H2 Console Special H2 Console Syntax Settings of the H2 Console Connecting to a Database using JDBC Creating New Databases Using the Server Using Hibernate Using Top. Link and Glassfish Using Eclipse. Link Using Apache Active. MQ Using H2 within Net. Beans Using H2 with j. OOQ Using Databases in Web Applications Android CSV (Comma Separated Values) Support Upgrade, Backup, and Restore Command Line Tools The Shell Tool Using Open. Office Base Java Web Start / JNLP Using a Connection Pool Fulltext Search User- Defined Variables Date and Time Using Spring OSGi Java Management Extension (JMX)Starting and Using the H2 Console The H2 Console application lets you access a database using a browser.
Let us see the example on hibernate select query, hibernate loading an object, selecting object from the database in hibernate, hibernate loading data from database. A simple example to submit multiple rows in form using Spring 3 MVC. It uses List of beans to submit an array of rows to Spring Controller. This chapter describes the Oracle performance extensions to the Java Database Connectivity (JDBC) standard. This section compares and contrasts the general models and.
This can be a H2 database, or another database that supports the JDBC API. A browser window should open and point to the login page at http: //localhost: 8. Windows Open a file browser, navigate to h. A console window appears.
If there is a problem, you will see an error message in this window. A browser window will open and point to the login page (URL: http: //localhost: 8.
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Any Double click on the h. This only works if the . Java. Any Open a console window, navigate to the directory h.
Firewall If you start the server, you may get a security warning from the firewall (if you have installed one). If you don't want other computers in the network to access the application on your machine, you can let the firewall block those connections. The connection from the local machine will still work. Only if you want other computers to access the database on this computer, you need allow remote connections in the firewall. A workaround is to connect using 'localhost'.
To change this, go to 'Preferences' and select 'Allow connections from other computers'. Testing Java To find out which version of Java is installed, open a command prompt and type. If you get an error message, you may need to add the Java binary directory to the path environment variable. Error Message 'Port may be in use' You can only start one instance of the H2 Console, otherwise you will get the following error message: . Possible cause: another server is already running..
It is possible to start multiple console applications on the same computer (using different ports), but this is usually not required as the console supports multiple concurrent connections. Using another Port If the default port of the H2 Console is already in use by another application, then a different port needs to be configured. The settings are stored in a properties file.
For details, see Settings of the H2 Console. The relevant entry is web. Port. If the default port is already in use, a random port is used. Connecting to the Server using a Browser If the server started successfully, you can connect to it using a web browser. Javascript needs to be enabled.
If you started the server on the same computer as the browser, open the URL http: //localhost: 8. If you want to connect to the application from another computer, you need to provide the IP address of the server, for example: http: //1. If you enabled TLS on the server side, the URL needs to start with https: //.
Multiple Concurrent Sessions Multiple concurrent browser sessions are supported. As that the database objects reside on the server, the amount of concurrent work is limited by the memory available to the server application. Login At the login page, you need to provide connection information to connect to a database.
Set the JDBC driver class of your database, the JDBC URL, user name, and password. If you are done, click .
The settings are stored in a properties file (see Settings of the H2 Console). Error Messages Error messages in are shown in red. You can show/hide the stack trace of the exception by clicking on the message.
Adding Database Drivers To register additional JDBC drivers (My. SQL, Postgre. SQL, HSQLDB..), add the jar file names to the environment variables H2. DRIVERS or CLASSPATH. Example (Windows): to add the HSQLDB JDBC driver C: \Programs\hsqldb\lib\hsqldb. H2. DRIVERS to C: \Programs\hsqldb\lib\hsqldb. Spaces in the path names are supported. The settings must not be quoted.
Using the H2 Console The H2 Console application has three main panels: the toolbar on top, the tree on the left, and the query/result panel on the right. The database objects (for example, tables) are listed on the left. Type a SQL command in the query panel and click . The result appears just below the command. Inserting Table Names or Column Names To insert table and column names into the script, click on the item in the tree. If you click on a table while the query is empty, then SELECT * FROM ..
While typing a query, the table that was used is expanded in the tree. For example if you type SELECT * FROM TEST T WHERE T. Disconnecting and Stopping the Application To log out of the database, click .
However, the server is still running and ready to accept new sessions. If you don't have the system tray icon, navigate to . Special H2 Console Syntax The H2 Console supports a few built- in commands. Those are interpreted within the H2 Console, so they work with any database.
Built- in commands need to be at the beginning of a statement (before any remarks), otherwise they are not parsed correctly. If in doubt, add ; before the command. Command(s)Description @autocommit. Patterns are case sensitive (usually identifiers are uppercase).
For information about the parameters, see the Javadoc documentation. Missing parameters at the end of the line are set to null. The complete list of metadata commands is: @attributes, @best. Parameters (?) are set using a loop from 0 up to x - 1. Random values are used for each ?/*rnd*/. A Statement object is used instead of a Prepared.
Statement if @statement is used. Result sets are read until Result. Set. next() returns false. Timing information is printed.
This will call System. The statement is not executed. The top 3 stack traces of the statement(s) between start and stop are listed (if there are 3). Used to profile a long running query or operation that is running in another session (but in the same process). Settings of the H2 Console The settings of the H2 Console are stored in a configuration file called . For Windows installations, the user home directory is usually C: \Documents and Settings\.
The configuration file contains the settings of the application and is automatically created when the H2 Console is first started. Supported settings are: web. Allow. Others: allow other computers to connect. Example: 1=Generic H2 (Embedded). A simple way to do that is using the following code.
Test . The driver name is . The database URL always needs to start with jdbc: h. The second parameter in the get. Connection() call is the user name (sa for System Administrator in this example).
The third parameter is the password. In this database, user names are not case sensitive, but passwords are. Creating New Databases By default, if the database specified in the URL does not yet exist, a new (empty) database is created automatically. The user that created the database automatically becomes the administrator of this database.
Using the Server H2 currently supports three server: a web server (for the H2 Console), a TCP server (for client/server connections) and an PG server (for Postgre. SQL clients). Please note that only the web server supports browser connections.
The servers can be started in different ways, one is using the Server tool. Starting the server doesn't open a database - databases are opened as soon as a client connects. Starting the Server Tool from Command Line To start the Server tool from the command line with the default settings, run. Server. This will start the tool with the default options. To get the list of options and default values, run.
Server - ? Connecting to the TCP Server To remotely connect to a database using the TCP server, use the following driver and database URL: JDBC driver class: org. Driver. Database URL: jdbc: h. For details about the database URL, see also in Features.
Simplify the DAO with Spring and Java Generics. I usually post about Persistence on Twitter - you can follow me there: Follow @baeldung. Table of Contents. Overview. This article will focus on simplifying the DAO layer by using a single, generified Data Access Object for all entities in the system, which will result in elegant data access, with no unnecessary clutter or verbosity. The Hibernate and JPA DAOs.
Most production codebases have some kind of DAO layer. Usually, the implementation ranges from multiple classes with no abstract base class to some kind of generified class. However, one thing is consistent – there is always more than one – most likely, there is a one to one relation between the DAOs and the entities in the system. Also, depending on the level of generics involved, the actual implementations can vary from heavily duplicated code to almost empty, with the bulk of the logic grouped in a base abstract class.
These multiple implementations can usually be replaced by a single parametrized DAO used in such no functionality is lost by taking full advantage of the type safety provided by Java Generics. Two implementations of this concept are presented next, one for a Hibernate centric persistence layer and the other focusing on JPA. These implementations are by no means complete – only some data access methods are included, but they can be easily be made more thorough. The Abstract Hibernate DAOpublic abstract class Abstract.
Hibernate. Dao< T extends Serializable > . Using of templates, as well as management of the Session. Factory which is autowired in the DAO were covered in the Hibernate DAO tutorial. The Generic Hibernate DAONow that the abstract DAO is done, we can implement it just once – the generic DAO implementation will become the only implementation needed: @Repository.
Scope( Bean. Definition. SCOPE. This will mean that the clients get all the benefits of type safety without needing to create multiple artifacts for each entity. Second, notice the prototype scope of this generic DAO implementation.
Using this scope means that the Spring container will create a new instance of the DAO each time it is requested (including on autowiring). That will allow a service to use multiple DAOs with different parameters for different entities, as needed. The reason this scope is so important is due to the way Spring initializes beans in the container. Leaving the generic DAO without a scope would mean using the default singleton scope, which would lead to a single instance of the DAO living in the container. That would obviously be majorly restrictive for any kind of more complex scenario.
The IGeneric. Dao is simply an interface for all the DAO methods so that we can inject our implementation with Spring in (or in whatever is needed): public interface IGeneric. Dao< T extends Serializable> . The Abstract JPA DAOpublic abstract class Abstract. Jpa. Dao< T extends Serializable > . The Generic JPA DAOSimilar to the Hibernate implementation, the JPA Data Access Object is straightforward as well: @Repository. Scope( Bean. Definition.
SCOPE. Injecting this DAOThere is now a single DAO to be injected by Spring; also, the Class needs to be specified: @Service. Foo. Service implements IFoo. Service. After this point, the DAO is fully parametrized and ready to be used by the service. There are of course other ways that the class can be specified for the DAO – via reflection, or even in XML. My preference is towards this simpler solution because of the improved readability and transparency compared to using reflection. Conclusion. This article discussed the simplification of the Data Access Layer by providing a single, reusable implementation of a generic DAO. This implementation was presented in both a Hibernate and a JPA based environment.
The result is a streamlined persistence layer, with no unnecessary clutter. For a step by step introduction about setting up the Spring context using Java based configuration and the basic Maven pom for the project, see this article. I usually post about Persistence on Twitter - you can follow me there: Follow @baeldung.