Reverse Engineer Hibernate Value Object Mappings hbm.xml Examples Step 17

Reverse Engineer your Hibernate Mappings

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If you already have the database built, you can reverse engineer to create your value objects and your hibernate mappings. This will save you time in creating each of your value objects and mappings manually.

Eclipse has some tools to accomplish this. I used the openlogic plugin.
You should visit this website: https://openlogic.com/packages/eclipseplugin-hibernate_tools to retrieve the plugin.

This website is https so you will have to bypass the security warning.

You should download the openlogic-eclipseplugin-hibernate_tools-3.2.1.GA-all-bin-1.zip

Make sure you have the mysql.jar file you in your lib directory with the eclipse build path pointing to it. The eclipse plugin will need this to connect to the database.

When you download the plugin, you should unzip it and copy all of the directories and jar files from the plugins directory to the eclipse plugin directory.

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There are a couple of possible errors you can receive when using this plugin.
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1) java.lang.ClassNotFoundException: org.eclipse.jface.viewers.BaseLabelProvider

This error is because you are using an older version of eclipse. You will need to upgrade to a more current version of eclipse to use this plugin.

2) java.lang.ClassNotFoundException: org/eclipse/ui/internal/util/SWTResourceUtil

This error is because you are using a version of Ganymede Eclipse which is missing this class. You will need to add this class by following these steps:

2a) You need to get this class from an older version of Eclipse. I used the eclipse version 3.2.2. You should download this version or another version and locate this file in the eclipse plugin directory. org.eclipse.ui.workbench*.jar.


2b) Unzip this jar file and remove the SWTResourceUtil.class file.


2c) Locate the org.eclipse.ui.workbench_*.jar in your current eclipse directory. You should change the extension from jar to zip and then unzip it. Drop the class in the org/eclipse/ui/internal/util folder. Then zip it back up and change the extension back to .jar and place the jar file back in the plugin directory of eclipse.

3) Missing sun.nio.cs.surrogate

This error means that you didn't copy all of the jar files from the plugin into eclipse.
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After you have the plugin installed, then restart eclipse.
From my prior posts you should have already established a connection to the database using Hibernate.

After opening up eclipse, select windows->open perspective->other. Select Hibernate from the menu.

In the Hibernate Configuration window, select the right mouse button and select configuration.

Project: select the project you are working on.
Property file: If you are using a properties file, select it from here.
Configuration File: You need to select the configuration file that holds your database information.

Apply the changes.

Now we want to create your mappings directly from the database.

You should be able to select the database and see all the tables that you are using in your project from your configuration information in your hibernate mappings.

At the top menu you will see a drop down where you are able to select Hibernate Code Generation and Configuration. Select it to generate your mapping files.

On the Hibernate Code Generation link on the left, you should select the right mouse button and select new to open the configuration page.

In the Console Configuration, select hibernate.

Select what output directory you want to use. This is the directory where the mappings will be copied too. You should put them in the com.vo package which is the package holding your value objects.

Select the reverse enginner check box.

You can put the package in the configuration also and that will set the proper package name for the mappings.  Put the directory as the src directory and the tool will create the package for you.

You should select the exporters tab and select the Hiberante XML Mappings check box and Domain code.

You should press apply and then run to generate your mappings.

If you were unable to get the reverse engineering to work, then below I have the files you will need for this tutorial. If you do not reverse engineer, you can create the mappings manually.


If you reverse engineer, you will need to make sure you update the java objects to be the correct packages. You should also add a serializable variable "private static final long serialVersionUID=123l;" to each value object class.


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VO Objects and Mappings
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Book.java

package com.vo;
// Generated Oct 21, 2008 7:43:57 PM by Hibernate Tools 3.2.1.GA

import java.util.HashSet;
import java.util.Set;

/**
* Book generated by hbm2java
*/
public class Book implements java.io.Serializable {

private static final long serialVersionUID=123l;
private long id;
private Bookcategory bookcategory;
private String bookName;
private String bookAuthor;
private String bookPublisher;
private Set userses = new HashSet(0);

public Book() {
}

public Book(long id) {
this.id = id;
}

public Book(long id, Bookcategory bookcategory, String bookName,
String bookAuthor, String bookPublisher, Set userses) {
this.id = id;
this.bookcategory = bookcategory;
this.bookName = bookName;
this.bookAuthor = bookAuthor;
this.bookPublisher = bookPublisher;
this.userses = userses;
}

public long getId() {
return this.id;
}

public void setId(long id) {
this.id = id;
}

public Bookcategory getBookcategory() {
return this.bookcategory;
}

public void setBookcategory(Bookcategory bookcategory) {
this.bookcategory = bookcategory;
}

public String getBookName() {
return this.bookName;
}

public void setBookName(String bookName) {
this.bookName = bookName;
}

public String getBookAuthor() {
return this.bookAuthor;
}

public void setBookAuthor(String bookAuthor) {
this.bookAuthor = bookAuthor;
}

public String getBookPublisher() {
return this.bookPublisher;
}

public void setBookPublisher(String bookPublisher) {
this.bookPublisher = bookPublisher;
}

public Set getUserses() {
return this.userses;
}

public void setUserses(Set userses) {
this.userses = userses;
}

}

Book.hbm.xml

<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <!-- Generated Oct 21, 2008 7:44:22 PM by Hibernate Tools 3.2.1.GA --> <hibernate-mapping> <class name="Book" table="book" catalog="catalog"> <id name="id" type="long"> <column name="Id" /> <generator class="assigned" /> </id> <many-to-one name="bookcategory" class="Bookcategory" fetch="select"> <column name="BookCategoryId" /> </many-to-one> <property name="bookName" type="string"> <column name="BookName" length="50" /> </property> <property name="bookAuthor" type="string"> <column name="BookAuthor" length="50" /> </property> <property name="bookPublisher" type="string"> <column name="BookPublisher" length="50" /> </property> <set name="userses" inverse="false" table="userbook"> <key> <column name="BookId" not-null="true" /> </key> <many-to-many entity-name="Users"> <column name="UserId" not-null="true" /> </many-to-many> </set> </class> </hibernate-mapping>

Users.java

package com.vo;
// Generated Oct 21, 2008 7:43:57 PM by Hibernate Tools 3.2.1.GA

import java.util.HashSet;
import java.util.Set;

/**
* Users generated by hbm2java
*/
public class Users implements java.io.Serializable {
private static final long serialVersionUID=123l;
private long id;
private String firstName;
private String lastName;
private String middleName;
private String email;
private Set books = new HashSet(0);

public Users() {
}

public Users(long id) {
this.id = id;
}

public Users(long id, String firstName, String lastName, String middleName,
String email, Set books) {
this.id = id;
this.firstName = firstName;
this.lastName = lastName;
this.middleName = middleName;
this.email = email;
this.books = books;
}

public long getId() {
return this.id;
}

public void setId(long id) {
this.id = id;
}

public String getFirstName() {
return this.firstName;
}

public void setFirstName(String firstName) {
this.firstName = firstName;
}

public String getLastName() {
return this.lastName;
}

public void setLastName(String lastName) {
this.lastName = lastName;
}

public String getMiddleName() {
return this.middleName;
}

public void setMiddleName(String middleName) {
this.middleName = middleName;
}

public String getEmail() {
return this.email;
}

public void setEmail(String email) {
this.email = email;
}

public Set getBooks() {
return this.books;
}

public void setBooks(Set books) {
this.books = books;
}

}

Users.hbm.xml

<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <!-- Generated Oct 21, 2008 7:44:22 PM by Hibernate Tools 3.2.1.GA --> <hibernate-mapping> <class name="Users" table="users" catalog="catalog"> <id name="id" type="long"> <column name="Id" /> <generator class="assigned" /> </id> <property name="firstName" type="string"> <column name="FirstName" length="50" /> </property> <property name="lastName" type="string"> <column name="LastName" length="50" /> </property> <property name="middleName" type="string"> <column name="MiddleName" length="50" /> </property> <property name="email" type="string"> <column name="Email" length="50" /> </property> <set name="books" inverse="false" table="userbook"> <key> <column name="UserId" not-null="true" /> </key> <many-to-many entity-name="Book"> <column name="BookId" not-null="true" /> </many-to-many> </set> </class> </hibernate-mapping>

Bookcategory.java

package com.vo;
// Generated Oct 21, 2008 7:43:57 PM by Hibernate Tools 3.2.1.GA

import java.util.HashSet;
import java.util.Set;

/**
* Bookcategory generated by hbm2java
*/
public class Bookcategory implements java.io.Serializable {
private static final long serialVersionUID=123l;
private long id;
private String category;
private Set books = new HashSet(0);

public Bookcategory() {
}

public Bookcategory(long id) {
this.id = id;
}

public Bookcategory(long id, String category, Set books) {
this.id = id;
this.category = category;
this.books = books;
}

public long getId() {
return this.id;
}

public void setId(long id) {
this.id = id;
}

public String getCategory() {
return this.category;
}

public void setCategory(String category) {
this.category = category;
}

public Set getBooks() {
return this.books;
}

public void setBooks(Set books) {
this.books = books;
}

}

Bookcategory.hbm.xml

<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <!-- Generated Oct 21, 2008 7:44:22 PM by Hibernate Tools 3.2.1.GA --> <hibernate-mapping> <class name="Bookcategory" table="bookcategory" catalog="catalog"> <id name="id" type="long"> <column name="Id" /> <generator class="assigned" /> </id> <property name="category" type="string"> <column name="Category" length="50" /> </property> <set name="books" inverse="true"> <key> <column name="BookCategoryId" /> </key> <one-to-many class="Book" /> </set> </class> </hibernate-mapping>

After you have created all of your mappings, their are some possible issues that you will have to fix. See my next post for creating a DAO object and fixing any possible issues.

Go To Step 18