Transcript HIBERNATE/Java & ORACLE Overview of technology for Hibernate 3 as of 1/2006 By Joel A.

HIBERNATE/Java & ORACLE
Overview of technology for
Hibernate 3
as of 1/2006
By Joel A. Thompson ([email protected])
Goal:
Present Hibernate to first time users, and get you
started with all the major concepts right away.
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What we'll Cover
• Introduction of HibernateV3
Configuration & Setup of Hibernate/Java
• Code
• Pros and Cons
• RESOURCES
• Q & A.
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Intro:About
Hibernate
• www.hibernate.org - Open Source since, and
now with JBoss (since late 2003)
w/ commercial support & training.
Founder: Gavin King
• Provides a layer for java to interact with the
database.
– Is technically a set of java-class libraries that you use to
gain access to your database
• Hibernate caches database objects
– & Hibernate services your Java program
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Intro:About
Hibernate
• Hibernate layer resides in your JVM.
• Improves performance
– objects are cached in JVM and mapped to your
object model.
• Used in commercial applications
– JBoss for one (yes, another open source…)
– Many more opensource and commercial listed at:
http://www.hibernate.org/27.html
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Intro:About
Hibernate
• Hibernate is highly customizable
–
–
–
–
–
Caching (2nd level cache).
Database dialects
Transaction
Connection pooling
Custom Types
• Or use out of box (recommend changing: connection pooling).
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Intro:Importance
of DAO
• DAO: Data Access Objects –
design/pattern
• Purpose is to abstract your calls to the
database.
– Don't put SQL directly into your Java/JSP.
• You can change our database with minimal
affect on your code
• Identify bottle necks and bugs easier.
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Intro:Importance
of DAO
• Better design translates into easier to
understand code.
• Hibernate DAO - 3rd party technology
– Benefits of common knowledge
– Fixes to technology
– Specialized for each database and optimized for
database access (caveats).
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Intro:Comparison
to SQL
• Problem with SQL
– never lived up to promise of standardization amongst
database vendors
– Uses Jdbc to access database – (no forced design)
– Is Relational
• With Hibernate:
–
–
–
–
Caching
Easier to code
Standard access
Is Object Oriented and maps to Relational.
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Intro:Comparison
to SQL
• Speed/performance
– Prepared Statements and caching (hib)
– Can batch process many DML statements. (hib)
– Better performance from PL/SQL (sql/hib)
• Maintenance/Updates (hib)
• Legacy system (depends)
– Using hibernate with legacy database systems
& Legacy java code retrofit with Hibernate
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Configuration Hibernate/Java
• Download and install JDK 1.4 or 1.5
• Download version3 from
www.hibernate.org
• Setup Hibernate's Jars into your project's
classpath.
– The hibernate3.jar into your project's classpath;
and if need be all the <hib>/lib (if you don't
already have them).
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Config:hibernate.properties
• Make sure that Oracle's client jdbc lib is in
your CLASSPATH
• Hibernate.properties needs to be in your
project's & runtime classpath.
HIBERNATE.PROPERTIES
#for OCI (local instance of Oracle, not using tnsnames.ora).
hibernate.dialect=org.hibernate.dialect.OracleDialect
hibernate.connection.driver_class=oracle.jdbc.driver.OracleDriver
hibernate.connection.username=joel
hibernate.connection.password=xyz
hibernate.connection.pool_size=5
hibernate.connection.url=jdbc:oracle:oci:@
hibernate.show_sql=true
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Config: Download
& Config Xdoclet
[OPTIONAL]
• In order to run the "generation" of hibernate
XML you need to setup your classpath to include
Xdoclet libraries
• Download latest (v1.2.3) from
http://xdoclet.sourceforge.net/xdoclet/index.html
(www.xdoclet.org?)
– Download direct from
http://sourceforge.net/project/showfiles.php?group_id=31602
– Tag References
http://xdoclet.sourceforge.net/xdoclet/tags/hibernate-tags.html
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config: Download
& Config ANT
[OPTIONAL]
• In order to use ANT you'll need to setup your
PATH to include ANT. Check – run "ant"
• Download latest (v1.6.5) from http://ant.apache.org/
(www.ant.org?)
– Download direct from
http://www.axint.net/apache/ant/binaries/apache-ant-1.6.5-bin.zip
– Unzip and make sure "ant" is in your path. (right-click my computer ->
properties ->Advanced->Environmental Variables -> update PATH with directory
<ant_install>/bin)
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config: Download
& Config ANT
• SUMMARY:
– JDK [required]: PATH,CLASSPATH
– HIBERNATE [required]: CLASSPATH
• ORACLE or DBMS client [required]:
CLASSPATH (connection/lib info w/ hibernate.properties)
– XDOCLET [optional]:CLASSPATH
– ANT [optional]:CLASSPATH
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Code & Fragments
• What we'll cover in the CODE section. For
each of the items below you'll see the XML,
the DDL SQL, Java code and an
explanation.
–Single Entity
–Primary Keys
–Many-to-One
–Many-to-Many
–DML (Query, Insert, Update, Delete)
–Extra topics
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Code:
Overview
• Hibernate layer is
independent of your
code
• Entities map via
hibernate XML
• Hibernate & you:
DML, caching,
isolation levels
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Code[0]:
Java POJO Entity
public class Person {
Long PERSON_ID=null; //manufactured surrogate key
String FIRST_NAME=null;
String LAST_NAME=null;
Standard get/set
public Long getPERSON_ID(){…}
need empty
public void setPERSON_ID(String) {…}
public String getFIRST_NAME(){…}
constructor ~
public void setFIRST_NAME(String) {…}
public String getLAST_NAME(){…}
public void setLAST_NAME (String) {…}
}
&
See SAMPLE 0
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Code[0]:
XML for Entity
<!--Must be named: Person.hbm.xml and reside in CLASSPATH-->
<?xml
<?xml version="1.0"
version="1.0" encoding="UTF-8"?>
encoding="UTF-8"?>
<!DOCTYPE
hibernate-mapping
<!DOCTYPE hibernate-mapping PUBLIC
PUBLIC "-//Hibernate/Hibernate
"-//Hibernate/Hibernate Mapping
MappingDTD
DTD 3.0//EN"
3.0//EN""http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<hibernate-mapping>
<class name="com.rhinosystemsinc.hibernate.samples_0.Person" table="SAMPLE0_Person" >
<id name="PERSON_ID" column="PERSON_ID" type="java.lang.Long" unsaved-value="null">
<generator class="hilo">
class="hilo">
<generator
<paramname="table">SAMPLE0_PERSON_SEQ</param>
name="table">SAMPLE0_PERSON_SEQ</param>
<param
<paramname="column">NEXT</param>
name="column">NEXT</param>
<param
</generator>
</generator>
</id>
</id>
<property
<property
name="FIRST_NAME"
type="java.lang.String"
update="true"
insert="true"
column="FIRST_NAME"
not-null="true"
unique="false"
length="100"
/>
<property name="LAST_NAME"/>
</class>
</hibernate-mapping>
Define the manufactured
surrogate primary key,
based on SEQUENCE.
Also natural composite
primary keys:
<composite-id>
<key-property
name="name"/>
<key-property
name="ssn"/>
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</composite-id>
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Code:
Primary Keys
• All hibernate persisted Entity mappings
must have a primary key.
• Suggestion: Use surrogate generated keys.
– Hib supports natural keys ( & multi-column).
– Reason:
• Sometimes (rarely) keys will change values
• Easier to manage
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Code[0]:
Java Main Class
//SAVING A NEW OBJECT
org.hibernate.Session sess = sessFact.openSession(); //more on SessionFactory in a minute.
Person p = new Person();
p.setFIRST_NAME("John");
p.setLAST_NAME("Smith");
Transaction tx = sess.beginTransaction();
sess.saveOrUpdate(p);
tx.commit();
At this point, what if we
sess.close();
do an
update, via SQLPLUS?
See SAMPLE 0
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Code[0]:
Java 1-to-Many
public class Person {
Long PERSON_ID=null; //manufactured surrogate key
String FIRST_NAME=null;
String LAST_NAME=null;
Set ADDRESSES=null;
public Set getADDRESSES()
{
return ADDRESSES;
}
public void setADDRESSES(Set ADDRESSES)
{
this.ADDRESSES = ADDRESSES;
}
…//rest of get/set methods
}
NEW
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Code[0]:
Person XML 1-to-Many
…
<hibernate-mapping>
<class name="com.rhinosystemsinc.hibernate.samples_0.Person" table="SAMPLE0_Person" >
…
<set
name="ADDRESSES"
lazy="false"
inverse="true"
all or save-update-delete
cascade="save-update"
sort="unsorted"
Any records that don't have address will be shown too.
outer-join="true">
<key column="PERSON_ID"/>
Notice one-to-many ~
<one-to-many class="com.rhinosystemsinc.hibernate.samples_1.Address"/>
</set>
…
</class>
</hibernate-mapping>
NEW
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Code[0]:
public class Address {
Long ADDRESS_ID=null;
String STREET=null;
String APT_NO=null;
String CITY=null;
String STATE=null;
String ZIP=null;
Person person=null;// the person this address belongs to.
public Person getPerson()
{
return person;
}
public void setPerson(Person person)
{
this.person = person;
}
…//rest of get/set methods
}
Java 1-to-Many
New Address class
See Sample 1
Person reference ~
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Code[0]:
Address XML 1-to-Many
Address class
…usual header
<class name="com.rhinosystemsinc.hibernate.samples_1.Address"
table="SAMPLE1_Address" dynamic-update="true">
NOTICE different
<id name="ADDRESS_ID" column="ADDRESS_ID"
type="java.lang.Long" unsaved-value="null">
definition sample of
<generator class="sequence">
the sequence
<param name="sequence">SAMPLE1_ADDRESS_SEQ</param>
<param name="parameters">INCREMENT BY 1 START WITH 1</param>
</generator>
Notice variable name in Address class
</id>
<many-to-one name="person" class="com.rhinosystemsinc.hibernate.samples_1.Person"
For outer-join fetching or use 'select'
cascade="save-update"
fetch="join"
sequential select fetching. N+1 select prob.
will always be
lazy="false"
update="true"
eagerly fetched.
insert="true"
~
column="PERSON_ID"
not-null="false"/>
…rest of properties defined
See Sample 1
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Code[0]:
public static void main(String args[])
….
Address addr = new Address();
Person p = new Person();
p.setFIRST_NAME("John");
p.setLAST_NAME("Thompson");
p.setADDRESSES(new HashSet());
p.getADDRESSES().add(addr);
p.setCreated(new Date());
addr.setSTREET("12345 Easy");
addr.setCITY("Sacramento");
addr.setSTATE("CA");
addr.setORDER_POS(new Long(1));
addr.setCreated(new Date());
addr.setPerson(p);
…
sess.save(p);
tx.commit();
…
…
See Sample 1
main 1-to-Many
Create an empty "set" and assign to Person
Add the address to the "set"
assign person reference to address ~
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Code[0]:
Java Many-to-Many
public class Address {
…same as before
Set persons=null;// the person this address belongs to.
public Set getPersons()
{
return persons;
}
public void setPersons(Set persons)
{
this.persons = persons;
}
…//rest of get/set methods
}
See Sample 2
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NEW ~
Code[0]:
XML Many-to-Many
…usual header
<class name=...Address>
"Set persons=null" in java
<set name="persons"
Intermediate M-M table
table="SAMPLE2_PERSON_ADDRESS">
<key column="ADDRESS_ID"/>
M-M definition,
<many-to-many
class="com.rhinosystemsinc.hibernate.samples_2.Person" referencing the Person
class by PERSON_ID
column="PERSON_ID"/>
~
</set>
…rest of properties defined
</class>
</hibernate-mapping>
See Sample 1
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Code[0]:
Address addr = new Address();
Person p = new Person();
p.setFIRST_NAME("John");
p.setLAST_NAME("Thompson");
p.setADDRESSES(new HashSet());
p.getADDRESSES().add(addr);
p.setCreated(new Date());
addr.setSTREET("12345 Easy");
…
//revised! for many-to-many
addr.setPersons(new HashSet());
addr.getPersons().add(p);
//ADD NEW PERSON TO ADDRESS
Person p2=new Person();
p2.setFIRST_NAME("Martha");
p2.setLAST_NAME("Thompson");
p2.setADDRESSES(new HashSet());
p2.getADDRESSES().add(addr);
addr.getPersons().add(p2);
See Sample 1
Main Many-to-Many
Setup empty Address and Person object
Create empty list of Addresses
Martha also lives at the SAME address,
here we add the address to the p2 object
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~
Code[0]:
Reference Data
• Data that doesn't change usually loaded at system
installation time. (Use 2nd level Cache).
– Examples: STATES, CATEGORY, ZIP..etc.
• Strategy
– Setup XML class with element cache as read-only
– Setup cache for relation as read-only
– Call a method to load All read-only objects at
initialization (actually even everytime).
(for example…)
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Code[0]:
Reference Data
…
<class name="com.rhinosystemsinc.sample.Event">
For the EVENT class
…
<many-to-one
Variable name for java class
name="CATEGORY"
Category CATEGORY=null;
class="com.rhinosystemsinc.sample.Category"
cascade="none"
which operations should be cascaded from
update="false"
the parent object to the associated object
insert="false"
We will not update or insert from this relationship. ~
column="CATEGORY_ID"
not-null="true" />
</class>
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Code[0]:
Reference Data
For the CATEGORY class
…
<class name="com.rhinosystemsinc.sample.Category" mutable="false">
<cache usage="read-only" />
…
</class>
Set cache to be read-only
Also - notice no need for a reference back to Event class
---------------------------------------------------------------------------------------------------------In your Java code, load the objects at least once…
…
org.hibernate.Query q = sess.createQuery("from Category");
q.setCacheMode(org.hibernate.CacheMode.NORMAL);
q.setCacheable(true);
java.util.List result = q.list();
Make sure your Query sets up the CACHING! (2nd level) ~
…
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Code:
Components
• Components
"Fine-grained object Model" - more Classes than Tables
– Value Type – not Entity reference
• Meaning, you want separate Java class (from the main entity)
for this property, and yet it is stored in DB with main entity
• Lets Consider ZIP_CODE as example.
• Address w/ ZipCode attribute
• ZipCode defines ZIP_CODE and ZIP_4DIGIT_CODE as fields
• Address Table has two fields in table (w/ same field names).
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Code:
Component (example)
//JAVA ADDRESS CLASS:
public class Address {
…
ZipCode variable, name is same as
ZipCode ZIP=null;
mapping below.
public ZipCode getZIP(){…}
public void setZIP(ZipCode ZIP)
}
//Address.hbm.xml -----------------------------------------------------------------------------------------…usual header
<class name="com.rhinosystemsinc.hibernate.samples_3.Address"
Notice use of "component", with class
table="SAMPLE3_Address" dynamic-update="true">
name ~
…
<component name="ZIP" class="com.rhinosystemsinc.hibernate.samples_3.ZipCode">
…
</class>
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Code:
Component (example)
//Java ZipCode Class
public class ZipCode {
NO ID
// Components have NO ID...they are just entirely dependent on
// containing Entity - in this case Address - in otherwords,
// we want a Java Class representation of ZipCode, but want it
// mapped into the Address table with ZIP_CODE and ZIP_4DIGIT_CODE
// as attributes of Address table.
String ZIP_CODE = "";
String ZIP_4DIGIT_CODE = "";
public String getZIP_4DIGIT_CODE(){…}
public void setZIP_4DIGIT_CODE(String ZIP_4DIGIT_CODE){…}
public String getZIP_CODE(){…}
public void setZIP_CODE(String ZIP_CODE){…}
}
Two attributes
w/
getters/setters
In this example: Attribute names map directly to database column names ~
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Code:
//SQL for Address table:
create table SAMPLE3_Address
(
ADDRESS_ID number primary key,
STREET varchar2(512),
APT_NO varchar2(64),
CITY varchar2(512),
STATE varchar2(2),
ZIP_CODE varchar2(5),
ZIP_4DIGIT_CODE varchar2(4)
);
Component (example)
Notice same name as
ZipCode variables. ~
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Code:
//Java Main Code
Address addr = new Address();
Person p = new Person();
p.setFIRST_NAME("John");
p.setADDRESSES(new HashSet());
p.getADDRESSES().add(addr);
addr.setSTREET("12345 Easy");
…
ZipCode zip=new ZipCode();
zip.setZIP_CODE("95603");
zip.setZIP_4DIGIT_CODE("4456");
addr.setZIP(zip);
addr.setPersons(new HashSet());
addr.getPersons().add(p);
…
sess.saveOrUpdate(p);
Component (example)
Usual initialization here.
Create a ZipCode
object, initialize it, and
set to the Address
Note: query returns an Address object w/
ZipCode filled in automatically. ~
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Code:
Querying
• Hibernate offers a variety of ways to query
the objects:
–
–
–
–
SQL – straight SQL (parsed SQL 92 standard)
HQL – hibernate's query language (SQL based)
QBE – query by example
Criteria Queries – Object oriented
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Code:
• HQL simple example:
Querying
Use the session to create the Query
object.
Query q = sess.createQuery("from Person");
java.util.List result = q.list();
Can also use ? As positional param
Then use:
// ALSO
First);
Query q = sess.createQuery("from Person pq.setString(0,
where
"
+
q.setString(1, Last);
"p.FIRST_NAME = :fname and " +
"p.LAST_NAME =:lname");
q.setString("fname", First); //can also use positional parameters
Returns a list, that you can iterate
q.setString("lname", Last);
through and cast the "objects" to
java.util.List result = q.list();
Person. ~
See all examples for quering
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Code:
Querying
• HQL scalar example (from reference.pdf):
Iterator results = sess.createQuery(
"select cat.color, min(cat.birthdate),
count(cat) from Cat cat " +
"group by cat.color").list().iterator();
while ( results.hasNext() )Notice alias "cat" lowercase
{
Object[] column = (Object[])
results.next();
Notice cast – same as attribute
Color type = (Color) column[0];
declared in Cat class ~
Date oldest = (Date) column[1];
Integer count = (Integer) column[2];
.....
}
See all examples for quering
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Code:
• SQL example:
SQL Querying
createSQLQuery
org.hibernate.SQLQuery q = sess.createSQLQuery("select *
" +
"
from SAMPLE0_PERSON" +
"
where " +
"
FIRST_NAME = :fname " +
Tell hibernate about actual "
and LAST_NAME = :lname");
class
q.addEntity(Person.class);
Bind parameters ~
q.setString("fname", First);
//can also use
positional parameters
q.setString("lname", Last);
See all examples for quering
java.util.List copyright
result2006,
= q.list();
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Code:
SQL Querying
• SQL example #2:
With Alias
org.hibernate.SQLQuery q = sess.createSQLQuery("select
{Person.*} " +
"
from SAMPLE0_PERSON Person where " +
"
Person.FIRST_NAME = :fname " +
"
See also:
and Person.LAST_NAME =:lname");
q.addScalar(String columnAlias, Type type).
q.addEntity("Person",Person.class);
q.addJoin(String alias, String path). Where path is the
q.setString("fname",
//can
also
path toFirst);
the java collection member
variable
name ofuse
the
parent class. In our example it would be
positional parameters
"Person.ADDRESSES" ~
q.setString("lname", Last);
java.util.List result = q.list();
… examples for quering
See all
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Pros/Cons
• Cons
– Lots of idiosyncrasies. – caching, flushing,
inverse…etc. (But can configure/disable them.)
– Learning curve is fairly steep.
(learn a way and stick with it).
– Not good for bulk-inserts (batch processing)
(forced to use PL/SQL within hibernate or jdbc)
– Java-XML-table all defining entity (good and
bad) – (xdoclet and other tools – setup system of generating base/core
code elements – use patterns and conventions)
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Pros/Cons
• Pros
– Simple to understand concepts.
– Stick with tools and frameworks, then can speed up
development time.
– Caching for you – so better performance.
(if you don’t use cache, then similar to straight SQL w/ preparedstatement
performance).
– Highly extensible and customizable to suite your needs
for new development and conversion.
– Defacto standard, via OpenSource LGPL license, non
proprietary, and known by developer community
(cost, maintenance, bugs..etc.)
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Resources
• Hibernate.org – is the best most up-to-date
– FAQs : http://www.hibernate.org/5.html
• Advanced Problems, Tips and Tricks, Performance and more…
• Evaluation- http://www.hibernate.org/263.html
– Doc link: http://www.hibernate.org/5.html
– Migration (A MUST!) – http://www.hibernate.org/250.html
• Package change: net.sf -> org.hibernate
• SessionFactory
• Criteria Query
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Resources
• Hibernate installation
– <installdir>/doc/{api,other,reference}/en/pdf/hibernate_reference.
pdf (great for reference, yet not sufficient for beginners to "learn").
– <installdir>/eg – samples
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Resources
• Miscellaneous
– Book: Hibernate In Action http://www.manning.com/bauer
– Performance #'s:
http://www.sourcelabs.com/?sidemenu=3&page=software&sub=sash_hibernateperftest
• Hibernate user FORUM - http://forum.hibernate.org/
(+200 msg/day)
• CaveatEmptor Sample from Hibernate:
http://caveatemptor.hibernate.org/
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End 0f Presentation
Thank you!
• Extra topics session follow, if time.
~ Or ~
• Q&A
• Future Questions:
email:
[email protected]
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XDoclet
• XDoclet is used to generate hibernate XML
files.
– You specify annotation tags in your Java code
– Run an xdoclet-ANT task on the java code
– Make sure xml is in your classpath (the xdocletant will put in src directory)
• Hibernate Annotations, next step.
See all examples of Xdoclet in the java code
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XDoclet example
•Person.java
Long PERSON_ID=null;
String FNAME=null;
/** @hibernate.id
@hibernate.id
/**
unsaved-value="null"
** unsavedvalue="null"
* generatorclass="sequence"*/
* generatorpublic
class="sequence"*/
Long
get
public
Long getPERSON_ID(){}
public void
/** @hibernate.property */
setPERSON_ID(Long){}
/** @hibernate.property */
• Person.hbm.xml
Xdoclet Ant
task
<id name="PERSON_ID"
column="PERSON_ID"
type="java.lang.Long"
unsaved-value="null">
<generator class="sequence">
<!– …some xdoclet
commentary…-->
commentary…-->
</generator>
</id>
<property
<property
name="LAST_NAME"
name="LAST_NAME"
type="java.lang.String"
type="java.lang.String"
update="true"
update="true"
insert="true"
insert="true"
column="LAST_NAME"
/> column="LAST_NAME"
/>
public String
getFNAME(){}
•Maintain tags in one location - Java
public void
setFNAME(String){}
•On building (one click) create hbm.xml
See all examples for xdoclet
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rhinosystemsinc.com all rights
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files
Topics Not Covered
•
•
•
•
•
SessionFactory
PLSQL
Custom UserType
Caching (1st & 2nd Level)
Transactions and
Isolation Levels
– JDBC trx semantics
– Concurrent Updates and
versioning.
• Session and Flushing
– Session "unit of work"
• Interceptors & Logging
• Definitions:
– Transient, Persistent,
Detached
• Subclass
copyright 2006,
rhinosystemsinc.com all rights
reserved