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HibernateRelationshi...




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At line 2 changed 1 line.
This is a tutorial to show how to create and manage Hibernate relationships within [AppFuse]. This tutorial was written for AppFuse 1.8 and the AppGen pieces may not work with previous versions.
This is a tutorial to show how to create and manage Hibernate relationships within [AppFuse]. This tutorial was written using AppFuse 1.8.2. All of the code for this tutorial is downloadable at [http://static.appfuse.org/downloads/appfuse-hr.zip].
At line 4 changed 1 line.
;:''For further details about the specifics regarding creating entities, XDoclet tags for Hibernate, DAO development, etc., please refer to [Creating new DAOs and Objects in AppFuse|CreateDAO].''
;:''For further details about the specifics regarding creating objects, XDoclet tags for Hibernate, DAO development, etc., please refer to [Creating new DAOs and Objects in AppFuse|CreateDAO].''
At line 6 added 2 lines.
%%note __NOTE:__ Copying the Java code in this tutorials [doesn't work in Firefox|http://raibledesigns.com/page/rd?anchor=java2html_plugin_for_jspwiki_causes]. A workaround is to CTRL+Click (Command+Click on OS X) the code block and then copy it.%%
At line 7 changed 2 lines.
* [1] Create Weblog.java, Entry.java and add XDoclet tags
* [2] [[Many-to-One] Create a new Category object and modify Entry.java to use it
* [1] Create Weblog.java, Entry.java and Category.java domain objects
* [2] [[Many-to-Many] A Weblogs can have many Users, a User can have many Weblogs
At line 10 changed 3 lines.
* [4] [[Many-to-Many] ???
* [5] Lazy-Loading Issues
* [6] Managing relationships and indexed properties in the UI
* [4] [[Many-to-One] A Category object can be assigned to many entries
At line 15 removed 2 lines.
For our purposes, the Weblog entity is a list of available weblogs. A “Weblog” object has the following properties – an id, a username, a dateCreated, and a blogTitle. Every Entry object has an id, a text, and a timeCreated property.
The first thing to do is create some objects to persist. Let's create both a "Weblog" object and an “Entry” object (in the src/dao/**/model directory). Basic XDoclet tags for these entities are show as well.
At line 16 added 37 lines.
The ''Weblog'' object is used to indentify a person's blog. This class has the following properties:
* weblogId
* blogTitle
* dateCreated
The ''Entry'' object is used to contain a listing of a person's blog entries in their Weblog. This class contains the following properties:
* entryId
* text
* timeCreated
%%note __NOTE:__ The primary keys are prefixed with their entity name to avoid confusion. I generally recommend using "id" for your entities, but wanted to make thing clearer in this tutorial.%%
Below is a class diagram of these two objects, as well as the others you'll create in this tutorial.
[ER-Diagram.jpg]
The first thing you need to do in this tutorial is these two object to persist. Create a __Weblog.java__ class and an __Entry.java__ class (in the src/dao/**/model directory). The necessary XDoclet tags for these entities is included on the ''getter'' method's javadoc. You can download these files using the links below. Note that javadocs have been eliminated for brevity.
* [Download Weblog.java|Weblog.java]
* [Download Entry.java|Entry.java]
;:''Rather than fill up this tutorial with large blocks of Java code, the necessary files are attached and linked to. Small code snippets are used where appropriate. You should be able to easily download the files by right-clicking on them and selecting "Save Target As...".''
Create a __Category.java__ object to act as an entity for persisting category information about weblog entries. Each category can have many entries. This class contains the following properties:
* categoryId
* name
* description
* [Download Category.java|Category.java]
!Configure Spring
Add the 3 new mapping files (that will be generated) to the "sessionFactory" bean's ''mappingResources'' property in __src/org/appfuse/dao/hibernate/applicationContext-hibernate.xml__.
At line 20 changed 1 line.
package org.appfuse.model;
<property name="mappingResources">
<list>
<value>org/appfuse/model/Role.hbm.xml</value>
<value>org/appfuse/model/User.hbm.xml</value>
<value>org/appfuse/model/Weblog.hbm.xml</value>
<value>org/appfuse/model/Entry.hbm.xml</value>
<value>org/appfuse/model/Category.hbm.xml</value>
</list>
</property>
}]
At line 22 changed 1 line.
import java.util.Date;
!![[Many-to-Many] A Weblogs can have many Users, a User can have many Weblogs [#2]
At line 24 changed 4 lines.
import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
import org.apache.commons.lang.builder.ToStringBuilder;
import org.apache.commons.lang.builder.ToStringStyle;
A Weblog can have many Users. Basically the idea is of a shared weblog that is a place where many users can express themselves about a particular topic of interest. For this bit of functionality the User object will be modified to have a many-to-many relationship with Weblog.
At line 29 changed 4 lines.
/**
* @hibernate.class table="weblog"
*/
public class Weblog extends BaseObject {
Add the following ''users'' property and accessor methods to __Weblog.java__.
At line 34 changed 5 lines.
private Long id;
private String username;
private Date dateCreated;
private String blogTitle;
private Integer version;
[{Java2HtmlPlugin
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/**
* @return Returns the blogTitle.
*
* @hibernate.property column="blog_title"
*/
public String getBlogTitle() {
return blogTitle;
}
private List users = new ArrayList();
/**
* @hibernate.bag table="weblog_user" cascade="save-update" lazy="true"
* @hibernate.collection-key column="weblog_id"
* @hibernate.collection-many-to-many class="org.appfuse.model.User" column="username"
*/
public List getUsers() {
return users;
}
At line 49 changed 7 lines.
/**
* @param blogTitle
* The blogTitle to set.
*/
public void setBlogTitle(String blogTitle) {
this.blogTitle = blogTitle;
}
public void addUser(User user) {
getUsers().add(user);
}
At line 57 changed 8 lines.
/**
* @return Returns the dateCreated.
*
* @hibernate.property column="date_created"
*/
public Date getDateCreated() {
return dateCreated;
}
public void setUsers(List users) {
this.users = users;
}
}]
At line 66 changed 7 lines.
/**
* @param dateCreated
* The dateCreated to set.
*/
public void setDateCreated(Date dateCreated) {
this.dateCreated = dateCreated;
}
%%note __NOTE:__ The reason a java.util.List is used instead of a java.util.Set is because this is because [Sets aren't supported for indexed properties in Struts|http://www.mail-archive.com/[email protected]/msg26289.html].%%
At line 74 changed 9 lines.
/**
* @return Returns the id.
*
* @hibernate.id column="weblog_id" generator-class="native"
* unsaved-value="null"
*/
public Long getId() {
return id;
}
!User modifications
At line 84 changed 7 lines.
/**
* @param id
* The id to set.
*/
public void setId(Long id) {
this.id = id;
}
To allow navigation from a User objec to a list of Weblogs, you need to add a List of Weblogs to the User object. Modify ''User.java'' to add a ''weblogs'' List and accessor methods.
At line 92 changed 6 lines.
/**
* @return Returns the username.
*/
public String getUsername() {
return username;
}
[{Java2HtmlPlugin
At line 99 changed 7 lines.
/**
* @param username
* The username to set.
*/
public void setUsername(String username) {
this.username = username;
}
protected List weblogs;
At line 107 changed 8 lines.
/**
* @return Returns the version.
*
* @hibernate.version
*/
public Integer getVersion() {
return version;
}
/**
* @hibernate.bag table="weblog_user" cascade="save-update" lazy="true"
* @hibernate.collection-key column="username"
* @hibernate.collection-many-to-many class="org.appfuse.model.Weblog" column="weblog_id"
*/
public List getWeblogs() {
return weblogs;
}
At line 116 changed 7 lines.
/**
* @param version
* The version to set.
*/
public void setVersion(Integer version) {
this.version = version;
}
public void setWeblogs(List weblogs) {
this.weblogs = weblogs;
}
}]
At line 124 changed 13 lines.
/**
* @see java.lang.Object#equals(Object)
*/
public boolean equals(Object object) {
if (!(object instanceof Weblog)) {
return false;
}
Weblog rhs = (Weblog) object;
return new EqualsBuilder().append(this.blogTitle, rhs.blogTitle)
.append(this.username, rhs.username).append(this.dateCreated,
rhs.dateCreated).append(this.id, rhs.id).append(
this.version, rhs.version).isEquals();
}
!Test it!
At line 138 changed 8 lines.
/**
* @see java.lang.Object#hashCode()
*/
public int hashCode() {
return new HashCodeBuilder(-1229851019, 1071684527).append(
this.blogTitle).append(this.username).append(this.dateCreated)
.append(this.id).append(this.version).toHashCode();
}
Create a unit test so you can verify that everything actually works. Create a __WeblogDaoTest__ class in your test/dao/**/dao directory. This file should extend GenericDaoTest. If you're using anything less than AppFuse 1.9, you may have to modify GenericDAOTest's "dao" variable so its __protected__ instead of private. Copy the code below into this test:
At line 147 changed 10 lines.
/**
* @see java.lang.Object#toString()
*/
public String toString() {
return new ToStringBuilder(this, ToStringStyle.MULTI_LINE_STYLE)
.append("id", this.id).append("version", this.version).append(
"username", this.username).append("blogTitle",
this.blogTitle).append("dateCreated", this.dateCreated)
.toString();
}
[{Java2HtmlPlugin
package org.appfuse.dao;
import java.util.Date;
import org.appfuse.model.User;
import org.appfuse.model.Weblog;
public class WeblogDaoTest extends GenericDAOTest {
public void testWeblogAndUsers() throws Exception {
Weblog w = new Weblog();
w.setBlogTitle("My New Weblog");
w.setDateCreated(new Date());
// add it to the database
dao.saveObject(w);
w = (Weblog) dao.getObject(Weblog.class, w.getWeblogId());
assertTrue(w.getUsers().isEmpty());
// add a user
User u = (User) dao.getObject(User.class, "mraible");
w.addUser(u);
dao.saveObject(w);
w = (Weblog) dao.getObject(Weblog.class, w.getWeblogId());
assertTrue(w.getUsers().size() == 1);
// remove the user
w.setUsers(null);
dao.saveObject(w);
w = (Weblog) dao.getObject(Weblog.class, w.getWeblogId());
assertNull(w.getUsers());
}
At line 166 added 4 lines.
Make sure you run __ant setup-db__ before running __ant test-dao -Dtestcase=UserDAO__. When running the test, you'll probably get a ''LazyInitializationException''. To solve this, change BaseDaoTestCase to extend Spring's [AbstractTransactionalDataSourceSpringContextTests|http://www.springframework.org/docs/api/org/springframework/test/AbstractTransactionalDataSourceSpringContextTests.html] if it doesn't already. In additional, you'll need to make a few changes to the existing tests so all the tests pass. [Here is a patch|LazyDaoTests.diff]. At a minimum, you'll need to fix BaseDAOTestCase and GenericDAOTest (onSetUp() -> onSetupBeforeTransaction()).
Because the WeblogDaoTest is now extending AbstractTransactionalDataSourceSpringContextTests (ATDSSCT), there is a "jdbcTemplate" variable you can use to do additional querying. For instance, you could add the following at the end of your ''testWeblogAndUsers()'' method:
At line 162 changed 1 line.
package org.appfuse.model;
String qry = "select count(*) from weblog_user where username = 'mraible' " +
" and weblog_id = " + w.getWeblogId();
assertEquals(0, jdbcTemplate.queryForInt(qry));
}]
At line 164 changed 1 line.
import java.util.Date;
!![[One-to-Many] A Weblog object can have many Entries [#3]
At line 166 changed 4 lines.
import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
import org.apache.commons.lang.builder.ToStringBuilder;
import org.apache.commons.lang.builder.ToStringStyle;
Now you'll modify the __Weblog__ object and __Entry__ object to represent the multiplicity of a weblog that can have many entries. This relationship is set on the Weblog class using a java.util.List. XDoclet tags are used to establish this relationship using a __bag__ as the Hibernate collection type. Add the following code to your __Weblog.java__ class.
At line 171 changed 4 lines.
/**
* @hibernate.class table="entry"
*/
public class Entry extends BaseObject {
[{Java2HtmlPlugin
At line 176 changed 13 lines.
private Long id;
private String text;
private Date timeCreated;
private Integer version;
/**
* @return Returns the id.
*
* @hibernate.id column="entry_id" generator-class="native"
* unsaved-value="null"
*/
public Long getId() {
return id;
}
private List entries;
At line 190 changed 7 lines.
/**
* @param id
* The id to set.
*/
public void setId(Long id) {
this.id = id;
}
/**
* @return Returns the entries.
*
* @hibernate.bag name="entries" lazy="false" cascade="all"
* @hibernate.collection-key column="weblog_id"
* @hibernate.collection-one-to-many class="org.appfuse.model.Entry"
*/
public List getEntries() {
return entries;
}
At line 198 changed 8 lines.
/**
* @return Returns the text.
*
* @hibernate.property column="entry_text"
*/
public String getText() {
return text;
}
public void setEntries(List entries) {
this.entries = entries;
}
}]
At line 207 changed 7 lines.
/**
* @param text
* The text to set.
*/
public void setText(String text) {
this.text = text;
}
Modify the __Entry__ class is so it contains a foreign key to its parent __Weblog__ class.
At line 215 changed 8 lines.
/**
* @return Returns the timeCreated.
*
* @hibernate.property column="time_created"
*/
public Date getTimeCreated() {
return timeCreated;
}
[{Java2HtmlPlugin
At line 224 changed 4 lines.
/**
* @param timeCreated
* The timeCreated to set.
*/
private Long weblogId;
At line 229 changed 3 lines.
public void setTimeCreated(Date timeCreated) {
this.timeCreated = timeCreated;
}
/**
* @hibernate.property column="weblog_id"
*/
public Long getWeblogId() {
return weblogId;
}
At line 233 changed 8 lines.
/**
* @return Returns the version.
*
* @hibernate.version
*/
public Integer getVersion() {
return version;
}
public void setWeblogId(Long weblogId) {
this.weblogId = weblogId;
}
}]
At line 242 changed 7 lines.
/**
* @param version
* The version to set.
*/
public void setVersion(Integer version) {
this.version = version;
}
At this point, you could add an additional test method to WeblogDaoTest to test that this relationship works. Of course, you'll need to run __ant setup-db__ to make sure your database knows about the relationship.
At line 250 changed 12 lines.
/**
* @see java.lang.Object#equals(Object)
*/
public boolean equals(Object object) {
if (!(object instanceof Entry)) {
return false;
}
Entry rhs = (Entry) object;
return new EqualsBuilder().append(this.text, rhs.text).append(
this.timeCreated, rhs.timeCreated).append(this.id, rhs.id)
.append(this.version, rhs.version).isEquals();
}
!![[Many-to-One] A Category object can be assigned to many entries [#4]
At line 263 changed 8 lines.
/**
* @see java.lang.Object#hashCode()
*/
public int hashCode() {
return new HashCodeBuilder(-880342185, -1668369001).append(this.text)
.append(this.timeCreated).append(this.id).append(this.version)
.toHashCode();
}
The ''many-to-one'' relationship between __Category__ and __Entry__ can be established using XDoclet tags. Hibernate relationships can be established on either side of the relationship or bi-directionally. For this tutorial, this relationship is maintained by a __categoryId__ property and a __Category__ object in __Entry__. The list of possible categories for a weblog entry will eventually be represented as a drop-down on the UI. Add the following code to your __Entry.java__ class. Notice that the relationship to __Category__ has ''insert="false" update="false"''. This is because the object is read-only. This can be useful for displaying a category's name on the UI when you're viewing an Entry.
At line 272 changed 9 lines.
/**
* @see java.lang.Object#toString()
*/
public String toString() {
return new ToStringBuilder(this, ToStringStyle.MULTI_LINE_STYLE)
.append("text", this.text).append("id", this.id).append(
"version", this.version).append("timeCreated",
this.timeCreated).toString();
}
[{Java2HtmlPlugin
At line 282 changed 1 line.
}
private Long categoryId;
private Category category;
/**
* @hibernate.many-to-one insert="false" update="false" cascade="none"
* column="category_id" outer-join="true"
*/
public Category getCategory() {
return category;
}
public void setCategory(Category category) {
this.category = category;
}
/**
* @hibernate.property column="category_id"
*/
public Long getCategoryId() {
return categoryId;
}
public void setCategoryId(Long categoryId) {
this.categoryId = categoryId;
}
At line 285 changed 1 line.
!![[Many-to-One] Create a new Category object and modify Entry.java to use it [#2]
After making these changes, your __WeblogDaoTest__ should still pass. Verify it does by running __ant setup-db test-dao -Dtestcase=Weblog__.
At line 287 changed 1 line.
!![[One-to-Many] A Weblog object can have many Entries [#3]
''__Yeah baby, Yeah!__''
%%(color: green)
BUILD SUCCESSFUL\\
Total time: 24 seconds
%%
At line 289 changed 1 line.
!![[Many-to-Many] ??? [#4]
Before working on the UI, it's helpful to have some sample data so you don't have to do manual data entry. Add the following XML to the bottom of __metadata/sql/sample-data.xml__.
At line 291 changed 1 line.
!!Lazy-Loading Issues [#5]
<div style="color: blue !important; margin-left: 50px">
{{{
<table name='weblog'>
<column>weblog_id</column>
<column>blog_title</column>
<column>date_created</column>
<row>
<value>1</value>
<value><![CDATA[Sponge Bob is Cool]]></value>
<value>2004-03-31</value>
</row>
<row>
<value>2</value>
<value><![CDATA[Java Development = Fun]]></value>
<value>2005-01-05</value>
</row>
</table>
<table name='weblog_user'>
<column>weblog_id</column>
<column>username</column>
<row>
<value>1</value>
<value>tomcat</value>
</row>
<row>
<value>1</value>
<value>mraible</value>
</row>
<row>
<value>2</value>
<value>mraible</value>
</row>
</table>
<table name='category'>
<column>category_id</column>
<column>name</column>
<column>description</column>
<row>
<value>1</value>
<value><![CDATA[Struts vs. Spring MVC]]></value>
<value><![CDATA[Comparing implementations of the MVC Design Pattern]]></value>
</row>
<row>
<value>2</value>
<value><![CDATA[Cycling Notes]]></value>
<value><![CDATA[All about cycling in the US.]]></value>
</row>
<row>
<value>3</value>
<value><![CDATA[Cyclocross]]></value>
<value><![CDATA[Bog Trotters Unite!]]></value>
</row>
</table>
<table name='entry'>
<column>entry_id</column>
<column>entry_text</column>
<column>time_created</column>
<column>weblog_id</column>
<column>category_id</column>
<row>
<value>1</value>
<value><![CDATA[Testing]]></value>
<value>2005-04-11 01:02:03.4</value>
<value>1</value>
<value>1</value>
</row>
<row>
<value>2</value>
<value><![CDATA[Test Value]]></value>
<value>2005-04-12 01:02:03.4</value>
<value>1</value>
<value>1</value>
</row>
<row>
<value>3</value>
<value><![CDATA[Test Value 3]]></value>
<value>2005-04-12 01:02:03.4</value>
<value>2</value>
<value>3</value>
</row>
</table>
}}}
</div>
At line 293 changed 1 line.
!!Managing relationships and indexed properties in the UI [#6]
----
At line 350 added 1 line.
''Next Up:'' __Part II:__ [Create Weblog UI|HibernateRelationshipsUI] - Creating a UI to manage the relationships created in this tutorial.

Back to HibernateRelationships, or to the Page History.