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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 18 changed 1 line.
[{Java2HtmlPlugin
The ''Weblog'' object is used to indentify a person's blog. This class has the following properties:
At line 20 changed 1 line.
package org.appfuse.model;
* weblogId
* blogTitle
* dateCreated
At line 22 changed 1 line.
import java.util.Date;
The ''Entry'' object is used to contain a listing of a person's blog entries in their Weblog. This class contains the following properties:
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;
* entryId
* text
* timeCreated
At line 29 changed 4 lines.
/**
* @hibernate.class table="weblog"
*/
public class Weblog extends BaseObject {
%%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.%%
At line 34 changed 1 line.
private Long id;
Below is a class diagram of these two objects, as well as the others you'll create in this tutorial.
At line 36 changed 1 line.
private String username;
[ER-Diagram.jpg]
At line 38 changed 1 line.
private Date dateCreated;
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.
At line 40 changed 1 line.
private String blogTitle;
* [Download Weblog.java|Weblog.java]
* [Download Entry.java|Entry.java]
At line 42 changed 1 line.
private Integer version;
;:''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...".''
At line 44 changed 4 lines.
/*
* Generate your getters and setters using your favorite IDE: In Eclipse:
* Right-click -> Source -> Generate Getters and Setters
*/
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:
At line 49 changed 8 lines.
/**
* @return Returns the blogTitle.
*
* @hibernate.property column="blog_title"
*/
public String getBlogTitle() {
return blogTitle;
}
* categoryId
* name
* description
At line 58 changed 7 lines.
/**
* @param blogTitle
* The blogTitle to set.
*/
public void setBlogTitle(String blogTitle) {
this.blogTitle = blogTitle;
}
* [Download Category.java|Category.java]
At line 66 changed 8 lines.
/**
* @return Returns the dateCreated.
*
* @hibernate.property column="date_created"
*/
public Date getDateCreated() {
return dateCreated;
}
!Configure Spring
At line 75 changed 7 lines.
/**
* @param dateCreated
* The dateCreated to set.
*/
public void setDateCreated(Date dateCreated) {
this.dateCreated = dateCreated;
}
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 83 changed 9 lines.
/**
* @return Returns the id.
*
* @hibernate.id column="weblog_id" generator-class="native"
* unsaved-value="null"
*/
public Long getId() {
return id;
}
[{Java2HtmlPlugin
At line 93 changed 7 lines.
/**
* @param id
* The id to set.
*/
public void setId(Long id) {
this.id = id;
}
<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 101 changed 8 lines.
/**
* @return Returns the username.
*
* @hibernate.property column="username"
*/
public String getUsername() {
return username;
}
!![[Many-to-Many] A Weblogs can have many Users, a User can have many Weblogs [#2]
At line 110 changed 7 lines.
/**
* @param username
* The username to set.
*/
public void setUsername(String username) {
this.username = username;
}
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 118 changed 8 lines.
/**
* @return Returns the version.
*
* @hibernate.version
*/
public Integer getVersion() {
return version;
}
Add the following ''users'' property and accessor methods to __Weblog.java__.
At line 127 changed 7 lines.
/**
* @param version
* The version to set.
*/
public void setVersion(Integer version) {
this.version = version;
}
[{Java2HtmlPlugin
At line 135 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();
}
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 149 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();
}
public void addUser(User user) {
getUsers().add(user);
}
At line 158 changed 11 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();
}
}
public void setUsers(List users) {
this.users = users;
}
At line 94 added 6 lines.
%%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].%%
!User modifications
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 173 changed 1 line.
package org.appfuse.model;
protected List weblogs;
At line 104 added 22 lines.
/**
* @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;
}
public void setWeblogs(List weblogs) {
this.weblogs = weblogs;
}
}]
!Test it!
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:
[{Java2HtmlPlugin
package org.appfuse.dao;
At line 177 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;
import org.appfuse.model.User;
import org.appfuse.model.Weblog;
At line 182 changed 4 lines.
/**
* @hibernate.class table="entry"
*/
public class Entry extends BaseObject {
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 187 changed 1 line.
private Long id;
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()).
At line 189 changed 1 line.
private String text;
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 191 changed 1 line.
private Date timeCreated;
[{Java2HtmlPlugin
At line 193 changed 1 line.
private Integer version;
String qry = "select count(*) from weblog_user where username = 'mraible' " +
" and weblog_id = " + w.getWeblogId();
assertEquals(0, jdbcTemplate.queryForInt(qry));
}]
At line 195 changed 4 lines.
/*
* Generate your getters and setters using your favorite IDE: In Eclipse:
* Right-click -> Source -> Generate Getters and Setters
*/
!![[One-to-Many] A Weblog object can have many Entries [#3]
At line 200 changed 9 lines.
/**
* @return Returns the id.
*
* @hibernate.id column="entry_id" generator-class="native"
* unsaved-value="null"
*/
public Long getId() {
return id;
}
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 210 changed 7 lines.
/**
* @param id
* The id to set.
*/
public void setId(Long id) {
this.id = id;
}
[{Java2HtmlPlugin
At line 218 changed 8 lines.
/**
* @return Returns the text.
*
* @hibernate.property column="entry_text"
*/
public String getText() {
return text;
}
private List entries;
At line 227 changed 7 lines.
/**
* @param text
* The text to set.
*/
public void setText(String text) {
this.text = text;
}
/**
* @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 235 changed 8 lines.
/**
* @return Returns the timeCreated.
*
* @hibernate.property column="time_created"
*/
public Date getTimeCreated() {
return timeCreated;
}
public void setEntries(List entries) {
this.entries = entries;
}
}]
At line 244 changed 7 lines.
/**
* @param timeCreated
* The timeCreated to set.
*/
public void setTimeCreated(Date timeCreated) {
this.timeCreated = timeCreated;
}
Modify the __Entry__ class is so it contains a foreign key to its parent __Weblog__ class.
At line 252 changed 8 lines.
/**
* @return Returns the version.
*
* @hibernate.version
*/
public Integer getVersion() {
return version;
}
[{Java2HtmlPlugin
At line 261 changed 7 lines.
/**
* @param version
* The version to set.
*/
public void setVersion(Integer version) {
this.version = version;
}
private Long weblogId;
At line 269 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();
}
/**
* @hibernate.property column="weblog_id"
*/
public Long getWeblogId() {
return weblogId;
}
At line 282 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();
}
public void setWeblogId(Long weblogId) {
this.weblogId = weblogId;
}
}]
At line 291 changed 10 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();
}
}
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.
!![[Many-to-One] A Category object can be assigned to many entries [#4]
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.
[{Java2HtmlPlugin
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 303 changed 1 line.
Add some test data for testing purposes to sample-data.xml (in the metadata/sql directory)
After making these changes, your __WeblogDaoTest__ should still pass. Verify it does by running __ant setup-db test-dao -Dtestcase=Weblog__.
At line 256 added 8 lines.
''__Yeah baby, Yeah!__''
%%(color: green)
BUILD SUCCESSFUL\\
Total time: 24 seconds
%%
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 307 changed 1 line.
<table name='weblog'>
<table name='weblog'>
At line 311 removed 2 lines.
<column>username</column>
<column>version</column>
At line 317 removed 2 lines.
<value>tomcat</value>
<value>1</value>
At line 324 removed 2 lines.
<value>mraible</value>
<value>1</value>
At line 281 added 36 lines.
<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>
At line 332 changed 1 line.
<column>version</column>
<column>weblog_id</column>
<column>category_id</column>
At line 336 changed 2 lines.
<value>2005-04-11</value>
<value>1</value>
<value>2005-04-11 01:02:03.4</value>
<value>1</value>
<value>1</value>
At line 342 changed 2 lines.
<value>2005-04-12</value>
<value>1</value>
<value>2005-04-12 01:02:03.4</value>
<value>1</value>
<value>1</value>
At line 337 added 7 lines.
<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>
At line 349 changed 1 line.
!![[Many-to-One] Create a new Category object and modify Entry.java to use it [#2]
----
At line 351 changed 8 lines.
!![[One-to-Many] A Weblog object can have many Entries [#3]
!![[Many-to-Many] ??? [#4]
!!Lazy-Loading Issues [#5]
!!Managing relationships and indexed properties in the UI [#6]
''Next Up:'' __Part II:__ [Create Weblog UI|HibernateRelationshipsUI] - Creating a UI to manage the relationships created in this tutorial.

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