Transcript JAVA & PL/SQL For Oracle RDBMS (8i & 9i) By Joel A.

JAVA & PL/SQL
For Oracle RDBMS (8i & 9i)
By Joel A. Thompson ([email protected])
www.rhinosystemsinc.com
05/2004
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INTRODUCTION
Joel A. Thompson
 15 years of industry experience
 Consultant: Architecture, Software
Engineering and Project Manager
 Java and Oracle expert

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OVERVIEW
Basics of PLSQL
 Optimizing RDBMS Calls from JAVA

Return Values & Cursors
Logic processing on Server, ARRAY inserts
And more …
Examples
 WRAP UP / Q&A

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Getting Started with Java

Must install a JDK & IDE
– JDK (Java Developers Kit) from Sun
http://java.sun.com/j2se/1.4/index.html
– IDE (Integrated Developers Environment)
• Oracle’s JDeveloper (technet.oracle.com)
• IntelliJ: (www.intellij.net)
• Textpad: http://www.textpad.com
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Getting Started with Oracle

Server Install Oracle (Steps)
– Download/Install from technet.oracle.com
– Create the database, use Oracle's Database Configuration
Assistant.
– Make sure network listeners are started – typically your
instance will be available on port 1525 – use Oracle's Net
Configuration Assistant, to configure a "Listener".

Client Requirement
– Copy the $ORACLE_HOME/jdbc/lib/classes12.jar to your
client side's CLASSPATH.
– Connect string example (thin driver) – requires no client side
libraries: jdbc:oracle:thin:joel/welcome@localhost:1521:UCDBA
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Client Server Java/PLSQL Architecture
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What is PL/SQL?

A programming language
– If/then/else
– Loops
– Function calls
– Transactional
– Procedural
Feature rich
 Performance Gain
 Oracle only

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Some Good Reasons to use
PL/SQL






Basically you'd like to do some logic on the server side in one
call to the database
Transaction support within the PL/SQL
Temporary table queries/inserts to filter data further before
returning result set
Take advantage of server side resources while processing you
PL/SQL – send message out through Oracle's Advanced
Queuing.
Distributed Computing – update another database…
You want to abstract your database layer into Oracle, such
that you can change the table's or columns around without
affecting the client program.
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Ways to call PL/SQL

ADHOC
– Send the PL/SQL block of code from the client
java program to the server for processing.

FUNCTION
– Client Side calls a PL/SQL function in Oracle.
PL/SQL is already compiled and loaded in Oracle.
– Function will return a value

PROCEDURE
– Client calls a PL/SQL procedure
– Similar to function, but does not return values.
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ADHOC: Java Client Example 1

SQL embedded in call from Java Client
// EXAMPLE OF SIMPLE SELECT STATEMENT
Statement stmt=connection.createStatement();
// QUERY THE ENTIRE TABLE
String sSQL="select ACCOUNT_ID,SSNO,FNAME,LNAME,PHONE from PERSON order by account_id";
// GET THE RESULT SET AND PROCESS IT.
ResultSet rs=stmt.executeQuery(sSQL);
while(rs.next())
{
nPERSON_ID=rs.getInt(1);
sSSNO=rs.getString(2);
…/// check to see if matches with new account you'd like to add.
}
// IF ACCOUNT DOESN'T ALREADY EXIST, THEN ADD IT HERE:
stmt.executeUpdate("insert into PERSON(ACCOUNT_ID,SSNO,FNAME,LNAME) values(account_id_seq.nextval," +
"'" + sSSNO + "'," + "'" + sFNAME + "'," +"'" + sLNAME + "'");
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Issues Regarding Example 1
Selecting from entire table is generally a
bad idea. (unless small "lookup table").
 One call for the Query, and 2nd call to
create the account.

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ADHOC: Java Client Example 2

Prepared Statement/Bind from Java Client
public void initializeOnce()
{
// THE SQL INSERT TO BE MADE.
String sQueryNotify="insert into PERSON (PERSON_ID,SSNO,FNAME,LNAME)" +
" values (person_id_seq.nextval,?,?,?)";
// CREATE A PREPARED STATEMENT, BASED ON THE ABOVE SQL
m_psInsertPerson=conn.prepareStatement(sQueryNotify);
}
public void insertNewPerson(String SSNO,String FNAME,String LNAME)
{
// BIND THE PARAMETER - REUSE THE ALREADY CREATED PREPARED STATEMENT
m_psInsertPerson.setString(1, SSNO);
m_psInsertPerson.setString(2, FNAME);
m_psInsertPerson.setString(3, LNAME);
// EXECUTE THE INSERT
m_psInsertPerson.executeUpdate();
…
return;
}
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Issues Regarding Example 2
Good – Created the preparedStatement once
at initialization time & then binding values in
function.
 Loader routine purpose? – still worse
performance than a SQL batch processing.
 Does not check to see if account exists
already.
 GOOD – uses sequence number generation
from oracle

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ADHOC: Java Client Example 3

Query based on Prepared Statement
{ // IN CONSTRUCTOR or INITIALIZATION BLOCK
// THE SQL QUERY TO BE MADE.
String sQueryNotify="select email_author,notification,subject,s.name as name " +
" from project p, status s " +
"
where p.id=? " +
" and s.id=p.status_id";
// CREATE A PREPARED STATEMENT, BASED ON THE ABOVE SQL
m_psLookupProjectID=conn.prepareStatement(sQueryNotify);
}
public EmailInfo queryEmailInfo(int id)
{
// BIND THE PARAMETER
m_psLookupProjectID.setInt(1,id); // REUSE THE ALREADY CREATED PREPARED STATEMENT
// GET THE RESULT SET AND PROCESS IT.
ResultSet rs=m_psLookupProjectID.executeQuery();
…
return info;
}
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ADHOC: PL/SQL Example 4
PreparedStatement ps=null;
sSQL=new String("declare" +
"
l_id number:=0;" +
"
ret number:=0;" +
"
lssno varchar2(32):=?;" +
"
error_msg varchar2(1026):=null;" +
" BEGIN" +
" select count(*) into ret from person where SSNO= lssno ;" +
" if(ret=0) then" +
" insert into person(id,ssno) values(seq_id.nextval, lssno) returning id into ret;" +
" end if;" +
" ?:=ret;" +
" EXCEPTION WHEN OTHERS THEN" +
" ?:=SQLERRM;" +
" END;");
1
2
3
4
ps =connection.prepareStatement(sbSQL.toString());
int indx=1;
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ps.setString(indx++,SSNO);
int rettype=Types.INTEGER;
ps.registerOutParameter(indx++,rettype);
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rettype=Types.VARCHAR;
ps.registerOutParameter(indx++,rettype);
ps.executeUpdate();
l_sError=ps.getString(2);
if(l_sError!=null)
{
System.err.println("PL/SQL Error: " + l_sError);
return;
}else
{
ret=ps.getInt(1);
System.out.println("New USERID: " + ret);
}
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Analysis of Example 4

Refer to labels in red from example.
 1) Notice that "DECLARE" begins our PL/SQL code.
You don't need a DECLARE section, however, you
can setup variables here by binding them to Java
variables on your client side. Also notice the BEGIN
statement, which is matched with the "END;"
statement in #4.
DECLARE
…
BEGIN
…
END;
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Analysis of Example 4

Refer to labels in red from example.
 2) Test to see if the person exists before inserting
into the table. (notice the RETURNING clause on the
insert).
 3) If there are any exceptions that are thrown in the
surrounding block, then execute this line of code –
assign the ERROR MESSAGE (SQLERRM) to the
return message
 4) The "END" tag is used to close the BEGIN - Also
notice the usage of ";" after the END tag – also notice
that we finished the string.
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Analysis of Example 4

Refer to labels in red from example.
 5) Use an existing SQL connection to create the callable
statement – a prepared statement, used to bind input variables
and output variables.
Notice the index variable declared and assigned value of 1.

6) Bind the SSNO string to the first occurance of a "?" in the
PLSQL. (what will happen if SSNO string's length is greater than
32?).
Next few lines we register the output variables. (NOTICE how
they match up with the ?).
One is of type INTEGER the other VARCHAR.
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Analysis of Example 4

Refer to labels in red from example.
 7) We executed the SQL statement, and now check
for errors.
If we find an error Message (ie not null), then we will
report it, and return immediately. ELSE we'll continue
and report the new userid (created from a sequence
number in Oracle).
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Issues from Example 4

Constructing SQL on the client side.
– Need to recompile in order to change sql
– Not very portable.
– Not modular

Trade offs?
– Plain SQL insert and catch duplicate key
exception – need to make sure your
Primary KEY or unique indices are setup
properly.
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FUNCTION/PROCEDURE CALL – Example 5
Call a function, that processes some
data and returns a result set.
 KEY THINGS TO NOTE:

– Minimize SQL code on client side.
– Ready for portability
– Within Oracle – yes
– Using other database – perhaps
– SQL 92 syntax?
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Example 5 – Syntax consideration

JDBC SYNTAX For portability
{?= call <procedure-name>[<arg1>,<arg2>, ...]}
{call <procedure-name>[<arg1>,<arg2>, ...]}

ORACLE SYNTAX (not portable)
BEGIN ?:=<procedure-name>[<arg1>,<arg2>, ...];
END;
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Example 5 – PL/SQL server code
Load the following into oracle once at
install time
 Declare function in a package (not
necessary but good to do).

CREATE OR REPLACE PACKAGE api_person_pkg AS
TYPE T_REFCURSOR IS REF CURSOR;
-- Define a cursor reference.
FUNCTION getPeople (VARCHAR2) RETURN T_REFCURSOR;
END api_person_pkg;
/
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Example 5 – PL/SQL server code

Create the body of the package/function
CREATE OR REPLACE PACKAGE BODY api_person_pkg AS
FUNCTION function getPeople(p_filter varchar2:=null) RETURN T_REFCURSOR
IS
v_ret_cursor API_PERSON_PKG.T_REFCURSOR;
BEGIN
if (p_filter is null) then
OPEN v_ret_cursor FOR
'select * from person';
else
OPEN v_ret_cursor FOR
'select * from person where username like ''%' || p_filter || '%''';
end if;
RETURN v_ret_cursor;
END;
END api_person_pkg;
/

Consider using global temporary table. Create the table at install
time, then use the table to insert records into from different tables – the
records are only visible to current session. On commit records go away.
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Example 5 – PLSQL

Test code to test the PL/SQL
SQL> set serveroutput on;
SQL> declare
v_ret_cursor API_PERSON_PKG.T_REFCURSOR;
v_id number; --PERSON ID
v_name varchar2(120); -- the username
begin
v_ret_cursor:=API_PERSON_PKG.getPeople('jthomps');
LOOP
FETCH v_ret_cursor into v_id ,v_name;
EXIT WHEN v_ret_cursor%NOTFOUND;
dbms_output.put_line('values retrieved =' || v_id || ',' ||
v_name);
END LOOP;
END;
/
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Example 5 – java client code

Call a function to return a result set.
try
{
String sql=new String("{ ? = call api_person_pkg.getPeople('joelt') }");
// could have used "BEGIN ?:= api_person_pkg.getPeople('joelt'); END;"
final int cursorRefType=oracle.jdbc.driver.OracleTypes.CURSOR;
cs=m_Conn.prepareCall(sql);
cs.registerOutParameter(1,cursorRefType);
cs.execute();
rs=(ResultSet)cs.getObject(1);
int ColNameIndex=1;
ResultSetMetaData rsmd=rs.getMetaData();
String ColName1=rsmd.getColumnName(ColNameIndex++);
String ColName2=rsmd.getColumnName(ColNameIndex);
System.out.println(ColName1 + "," + ColName2);
while(rs.next())
{
l_sPersonID=rs.getString(1);
l_sUsername=rs.getString(2);
System.out.println(l_sPersonID + "," + l_sUsername);
}
}catch(SQLException sqle)
{ // ...
System.out.println("Error: " + sqle.getMessage());
}finally
{
rs.close();
cs.close();
try{ m_Conn.close(); } catch(Exception e){}
}
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Example 6 – objective

Java to insert/update record with stored
procedure, showing how to create primary
key & foreign key records using Oracle's
sequences.
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Example 6 – create the STR_VARRAY type

You need to create a type to hold the
array. This type will be referenced in
the PL/SQL procedure as a
parameter type, and in the Java
Code.
create or replace TYPE str_varray AS VARRAY(10) OF VARCHAR2(5)
/
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Example 6 – stored procedure

Create the stored procedure
PROCEDURE storePersonCar(p_username varchar2,p_Cars str_varray)
AS
cnt number:=0;
id person.id%TYPE;
indx integer;
BEGIN
select count(*) into cnt from person where username=p_username;
BEGIN
if ( cnt = 0 ) then
insert into person(id,username) values(seq_person_id.nextval,p_username) returning id
else
select id into id from person where username=p_username;
delete from cars where person_id=id;
end if;
indx:=p_Cars.FIRST;
while indx <= p_Cars.LAST LOOP
insert into cars values(id,p_Cars(indx));
indx:=p_Cars.next(indx);
END LOOP;
into id;
commit;
EXCEPTION WHEN OTHERS then
rollback;
END;
END;
/
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Example 6 –Java Code
import java.sql.*;
import oracle.sql.*;
…
PreparedStatement ps =null;
ArrayDescriptor desc = ArrayDescriptor.createDescriptor("JOEL.STR_VARRAY", m_Conn);
String sCar="";
String cars[]=new String[10];
for(int i=0;i<10;i++)
{
sCar="carX"+i;
// CONTRIVE A NAME of a CAR
cars[i]=new String(sCar);
}
ARRAY array3 = new ARRAY (desc, m_Conn, cars);
String sql=new String("{call api_person_pkg.storePersonCar('joelt',?) }");
ps= m_Conn.prepareStatement(sql);
// Set the values to insert
((oracle.jdbc.driver.OraclePreparedStatement)ps).setARRAY(1, array3);
// Insert the new row
ps.executeUpdate();
m_Conn.commit();
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Example 6 –Java Notes
Make sure to include classes12.jar and
nls_charset12.jar – both found in
$ORACLE_HOME/jdbc/lib directory.
 This example works with Oracle
9.2.0.1.0 on Windows XP.
 Java version 1.4.2_03

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Portability & Compatibility issues
SQL Standards
 JDBC standards
 Other issues (dates, functions…etc.)
 Portability from schema-to-schema

– abstracting calls to database with PL/SQL
layer
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WRAP-UP
QUESTIONS and Answers
 MORE INFORMATION:

– Contact: [email protected]
• Or call: 530-888-6248 x205
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