I am using hibernate in my servlet to access the database.DB contains lot of foreign keys, composite keys and backward references..
Can you suggest me some tools to do reverse engineer the MySQL DB to Object oriented file in java so that I can use it with hibernate.
I agree with Cris,
The version 0.5.5 of Minuteproject 4 JPA2 generates also for composite key a class annotated with #Embeddable. The entity class has the #EmbeddedId as entity with the reference to the Embeddable class. For the foreign keys part of the composite key, it generates the associated #MapsId.
Meanwhile the JPA2 templates do not cover yet the composite foreign key pattern.
Hope it helped.
IDEs usually provide such generating of entities.
For example, if you use Netbeans, just go File/New/Persistence/Entity Classes from Database within a Java SE/Java EE-Project to generate JPA entities.
By the way, it's a good idea to use standard JPA(2) mechanisms where possible, in order to not being dependant on a specific O/R-Mapper (such as Hibernate) or database.
Have a look at JBoss Hibernate Tools which allows you to reverse engineer existing databases.
The best one is MinuteProject in my opinion !
Check it on :
http://javacodesamples.wordpress.com/2011/02/04/jpa2-reverse-engineering-tool/
http://www.dzone.com/links/jpa2_reverseengineering_with_minuteproject_pragma.html
http://javacodesamples.wordpress.com/2010/09/04/minute-project-episode-1-the-productivity-provider/
It has also a Spring + Hibernate track beside the JPA so you can used that for you hibernate needs.
We use Hibernate Tools to generate *.hbm.xml files with the help of a hibernate.reveng.xml file. And then, we apply Hibernate Synchronizer plugin of Eclipse to generate Entities and DAOs using *.hbm.xml files.
hibernate.reveng.xml fill the parts where auto generation cannot guess what you have in your mind.
Hibernate Synchronizer has the main advantage of creating base classes for your generated entities/daos. You add your custom properties/methods to subclasses (again automatically generated) of the base classes. The advantage here, is if you make changes to your database and regenerate, the changes you make (to subclasses) rest untouched.
Whatever tool you choose pay attention to build a system where code generation is easy and painless, not only for the first time but also during advanced phases of the project. If not you'll lose all the advantages.
Related
I'd like to automatically generate Hibernate mappings for some Java classes I have. Basically, I'd like all objects in the class to have the equivalent of the #OneToOne annotation, and all collections to have the equivalent of the #OneToMany annotation by default. I'd like to be able to fine-tune this later, but 99% of my data works this way, and it would take a very long time to go through all the classes and add the annotations manually.
Is this possible?
edit: Sorry, I think omitted something very important: I'd actually like to generate these default annotations from classes, not from a database. I would still have to design about 40 tables if I were to start with the database, but I already have a package containing all those classes. Is it possible to generate the proper mappings based on existing Java classes?
Yes, in eclipse there is a plugin called hibernate tools from jboss, which can generate mapping from a existing database.
You can generate all hibernate files both xml and annotations variant.
Just Google Hibernate Tools to know how to use it.
Thanks !!
If you are creating new classes then you can create the database structure first and then create classes using database. In eclipse, hibernate provides Hibernate code generation feature. You can use that.
I'm new to hibernate and trying to understand what is the correct way to implement and use it.
Creates tables and then use a tool to generate Hibernate classes
or
Build the classes and create the tables
Our's is a legacy application, so the tables structure is already there..We are just creating the Hibernate classes and using them...
Can someone let me know which is correct and effecient way?
You have automated tools for both sides.
create the classes from a legacy database:
you should use this if you have a runnig database already.netbeans have one of these.
create the tables and relations from entity and embedded clasess:
this way you have to use anotations or a xml file to describe the relations betwen clases and other relational stuff and set table generation strategy to create in the persistence unit the tables will be created automatically usigng the names of the classes for the table and the names of the fields for the columns.
If you already have the database use the tool to generate entity classes
If you use Eclipse then here is a tool to generate POJOs from existing tables:
step by step auto code generation using eclipse plugin
If you are using Intellij check out Intellij Java Persistence API & Hibernate
Are there any tools that can look at a database, and generate the basic mapping files?
It would be great if it could take a database, and create the actual model (java classes) with annotations, but not sure if that exists?
Hibernate 3 has a toolset called Hibernate Tools that provides an Eclipse plugin and an Ant task that both support Reverse Engineering:
Reverse Engineering: The most powerful feature of Hibernate Tools is a database reverse engineering tool that can generate domain model classes and Hibernate mapping files, annotated EJB3 entity beans, HTML documentation or even an entire JBoss Seam application in seconds!
...
Ant task: The Hibernate3 tools include a unified Ant task that allows you to run schema generation, mapping generation, or Java code generation as part of your build.
For the Eclipse plugin, have a look at this section of the documentation. For the Ant task, have a look at the section about reverse engineering and optionally how to control it.
Note that other IDEs also provide support for reverse engineering (see Hibernate Reverse Engineering for Netbeans 6.5 and Generating Persistence Mappings from Database Schema for IntelliJ).
I just happened to stumble across this problem and I think I have found a perfect tool for the job.
http://hibernatepojoge.sourceforge.net/
Features : (in case you are lazy to go through the provided link)
Java objects representing each table using annotations for use with Hibernate.
A JUnit test case per table that uses the objects generated to create, populate, save, retrieve and compare results
DAO per class
The appropriate enumeration files
Spring and hibernate configuration
DAO layers
A data factory class per schema to return a pre-populated object with random data (for boundary checking, database population, etc)
Also supports:
Join tables including those with additional fields in link tables
Polymorphism/inheritance support
Composite Keys
One-To-One, many-to-one, many-to-many, etc
Multiple schema support (4 modes)
Natural Keys
Enumerations (including those entries which cannot be mapped cleanly onto the java world)
A whole bunch of more stuff (see sample.xml)
I would also like to say that setting this up is quite straight forward; You just have to have a hibernate configuration file and the jar file downloaded from the site. Then it's just a matter executing a jar file, passing the config.xml as a parameter!
If you are using eclipse or ant...
Jboss tools
You might find what you need here, I found it on the fly: MyGeneration.
I know there are others that exist, but I don'T remember by heart. Hope this helps!
IDEs like Netbeans allow generation of entity classes through a persistence context. If you had access to underlying generation method (not sure if it is an external tool or part of the IDE), could you generate database entity classes dynamically at runtime? The idea being that you could hook into the entity classes using reflection.
I know you can go the other way and generate the database from the entity class, however due to permissions issues in my work environment that would be a no go. However, if you reverse the process and pull the classes from the database it may be feasible in my environment. The idea being that the database would serve as a single point of configuration/control.
It's theoretically possible but what would be the point? Java is statically typed so you would only be able to use the generated classes by reflection and you would have no way of giving them behaviour, so removing the whole point of object-relational mapping. Loading the data into Maps or just using SQL record sets would be more convenient.
If you have an existing schema you can write classes that act in the way your application needs and declaratively map them onto the schema. That way the code is the simplest expression of your application logic and is persistence-agnostic.
You can find on JBoss website a tool to do the reverse engineering from database to java objects.
The source code is available, you should dig in!
https://www.jboss.org/tools/download/stable.html
Assuming you're using Hibernate, you might be able to use Hibernate Tools to generate the database schema. Although primarily designed for Eclipse and Ant, its theoretically possible to link it in and invoke it like any other JAR.
may i know in eclipse, is there any feature that will auto generate domain objects with all table relationship properly mapped in class?
can provide me with some reference articles on this?
You can use something like Hibernate to accomplish this
This plugin set for Eclipse called Hibernate Tools for Eclipse and ANT will do most of the work for you.
In particular it will do Reverse Engineering: The most powerful feature of Hibernate Tools is a database reverse engineering tool that can generate domain model classes and Hibernate mapping files, annotated EJB3 entity beans, HTML documentation or even an entire JBoss Seam application in seconds!
Telosys code generator does this kind of job.
It's an Eclipse plugin, it uses the database schema to create a light model
that is used to generate the Java code.
There are some predefined templates available on GitHub (for JPA, POJO, Documentation, Spring MVC, etc )
See http://www.telosys.org
and http://marketplace.eclipse.org/content/telosys-tools
Templates : https://github.com/telosys-templates-v3
Articles about code generation with Telosys :
https://modeling-languages.com/telosys-tools-the-concept-of-lightweight-model-for-code-generation/
https://dzone.com/articles/telosys-a-code-generation-tool-by-laurent-guerin
You can use Hibernate Tools 3.0.0.GA either via Eclipse or ANT to auto-generate your hibernate domain entities directly from your database tables.
See tutorial here :
http://docs.jboss.org/tools/3.0.0.GA/en/hibernatetools/html_single/index.html
I have a solution for you i.e to create auto generate domain objects with all table relationship properly mapped in class ...Try Dal4j yes you can find it in sourceforge.net/p/dal4j/wiki/ DAL4j is a Command Line and Framework tool that can be used to reverse engineer a MySQL or SQLServer database schema into a set of JPA Entity Beans.
DAL4j can be useful for scenarios where there is an existing database schema but a technology other that JPA is used by applications to interact with the database. DAL4j can provide an easy way to migrate your code base from other technologies such as JDBC or Hibernate to JPA.
The beans generated can be 1 or two types: Simple or Framework. Simple beans are standard pojo classes managed by your application using JPA semantics. Framework generated pojos use the DAL4j framework DAO generic to simplify CRUD operations.
DAL4j provides optional hooks to allow you integrate encryption/decryption of data fields that must be encrypted in the database.
Last, DAL4j provides a set of Generic classes that can be used to simplify creation of Session Beans which perform CRUD operations using generated Entities.
I think you will find this article feasible....
You want an object relational mapping of which Hibernate is the most popular for Java. The hibernate tools are typically better for taking annotated classes and using them to generate a schema, as opposed to vice versa, which is what you sound like you're doing. I suspect you'll be doing a lot of hand-annotating if you're working with a legacy DB schema.
if you use grails, you can generate domain objects with GRAG http://sourceforge.net/projects/grag
I use eclipse for java development, but when it comes to generating domain entities I use Net beans.
Create an EJB module, and then right click and generate entities.
You need to set up the database also you can select the tables you want visually.
Regards
Lyju
It feels like another rather common question that people always run into.
The link below links to a blog detailed enough for me to learn how to generate entities from database schema the first time.
http://shengwangi.blogspot.com/2014/12/how-to-create-java-classes-from-tables.html
Just in case, the following link refers to eclipse help page. This link should never expire:
http://help.eclipse.org/juno/index.jsp?topic=%2Forg.eclipse.jpt.doc.user%2Ftasks021.htm
I downloaded JBoss and failed to understand how it works. I think the plugin that I used is Hibernate Tools but I am not sure as I did not install any new plugin for this purpose. I am using Eclipse Luna for EE.
Hope this helps.
I got so tired of manually coding this kind of stuff so I made a tool to generate models, dao, and dao implementation from a schema. It's oriented towards spring boot and only tested on MySQL, but for those that don't want to use Hibernate and just want to work with jdbc/sql and JdbcTemplate, or just want POJOs with getter/setters generated for tables, then this could perhaps be something to kick off the coding.
Called Jassd (Java Automated Spring Source-code for Databases generator), I'm "jazzed" to introduce this tool: https://github.com/aforslund/jassd