Limit query for Java Persistence Query Language

Hi,
Anybody know Java Persistence Query Language can support limit querry to limit the number of row return(Like SQL LIMIT clause)?
Thanks

I think the javax.persistence.Query methods setFirstResult and setMaxResults are what you need...

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Tutorial for Java as a language for Portal development!

Hi All,
I am basically a Java, J2EE developer. Now my Employers want me to start working on SAP EP 6.0 SP9. The SAP world is completely new to me.
So
Plz, guide me and provide reference for some good Tutorials or books for Java coding in SAP EP.
Thanx in advance.
Manish

Hi Manish,
start here http://help.sap.com/saphelp_nw04/helpdata/en/19/4554426dd13555e10000000a1550b0/frameset.htm and work through the material.
The books offered by SAPPress for EP development are not recommandable.
SP9 should be upgraded, it's really horrible old and buggy.
Hope it helps
Detlev
PS: Wrong forum, you should have asked within EP Dev.
PPS: Please consider rewarding points for helpful answers on SDN. Thanks in advance!

Java Persistence 1.0 requires Java 5.0 or newer.

Hello All,
I'm getting the below error on NWDS CE 7.1 SP09 while trying to do the [tutorial, page 35|https://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/b030e7fb-2662-2b10-0dab-c4aa52c3550b]. I found a forum [posting|Problems adding Java Persistence as a Project Facet;, where the issue got resolved after restarting the laptop. I'm unable to get past this error even after bouncing the machine.
I'm using Java version: JDK1.5.0_06 and have also tried with 1.5.0_22
Java Persistence 1.0 requires Java 5.0 or newer.
Constraints for Java Persistence 1.0 have not been met.
Please help!
Regards,
TN

Hello there,
Can I ask you, Did you try closing and opening the NWDS again. Also try to clean and build the project again.
HTH
Vivek Nidhi

Persistence Query language

hi guys
I am using persistence query language, I'm trying to delete an entry from the database table. So far I tried 2 approaches
public void destroy(DeviceType deviceType)
em.merge(deviceType);
em.remove(deviceType);
public void delete(int pk)
em.createQuery("Delete from DeviceType dt where dt.deviceTypeID = '"+pk+"'");
both of these methods are not working for me.
please help

Hi shim1,
1. If you're executing destroy in an extended persistence context, em.merge(deviceType) is not needed. In a transaction scoped persistence context, you must change destroy to:
public void destroy(DeviceType deviceType)
DeviceType mergedType = em.merge(deviceType);
em.remove(mergedType);
Please see chapter 3.2.4.1 of the JPA specification for more information about the merge operation.
2. Please change the delete method to:
public void delete(int pk)
em.createQuery("Delete from DeviceType dt where dt.deviceTypeID = ?1").setParameter(1, new Integer(pk)).executeUpdate();
}

Query language for CTXRULE MATCHES

I am trying to build an alerting application when, on receipt of a new XML document, user's are alerted if the document matches one or more of the profiles that they have defined. I have created a CTXRULE index that does this but only with very simple profiles. For example ABOUT(soccer), which is the example in the Text documentation.
Is it possible to create more complex queries, for example using WITHIN to only match within defined elements of the XML document. Is there a definition of the query language that can be used with MATCHES and are there any good example?
Thanks
Martin Haigh

Omar,
Thanks for the reply. I had actually found that document myself but I couldn't get the WITHIN clause to work and that document conflicted with the ORACLE documentation at:
<a href="http://download-west.oracle.com/docs/cd/B10501_01/text.920/a96517/ind.htm#1010647> Do you have any examples of using WITHIN?
Thanks
Martin

Query language for XML documents

Which is a better (efficiency in terms of memory management) query language for interacting with XML documents.The query language shouls support 'insert', 'delete', 'update' and 'select' commands. How fast is database as compared to XML ( database being replaced by XML) when only 'insert' n 'select' commands are issued?

Hi,
I suggest you use the Sunopsis JDBC for XML driver that will let you perform all kind of SQL statements on your XML files. It is a type 4 driver so it's very use to use. You may have more information and download it here:
http://www.sunopsis.com/corporate/us/products/jdbcforxml/
Hope that will help
Simo Fernandez

Query language for XML that is going to remove use of database

Friends,
I want to know whether my idea is feasible or not.
I want to make a query language similar to SQL for XML which is going to remove the need for database for a large extent.
Their will be queries for making table,extracting data,making foreign key all through XML and no database.
I just want to know that is their any market value for such a project and will it be sellable,so that i can start working on it.

There is no way to judge any future market for such a thing.
As it is, XML is widely abused, having mutated from its original purpose, a markup language readable by both machine and human, to a general data interchange language. It winds up being extremely slow and convoluted, in some cases overwhelming the hardware when a simple and common error occurs, then having to catch up. A big part of this is the silly and redundant method of defining metadata, again and again and again and again.
So what you want to do is create a database which will be highly formatted with redundant information, dynamically. This is silly, why does data need to be stored in a human readable format? It doesn't always even need to be presented in a human readable format! Why the heck would you need to read the bits of an mp4? Steganography?
What you are proposing is the exact opposite of what is needed. What is needed is a way to describe metadata for many different kinds of data, in a manner that can be interpreted by both man and machine at appropriate times, extensible for various paradigms.
What can be sold, on the other hand, is another question entirely, and not technical at all.
First definition of database that pops up during a search: an organized body of related information
Why would you want to get rid of that?

SQL LIMIT query for Oracle

Hi,
Is there an Oracle equivilent to the LIMIT query ?
Basically, I want to limit the number of rows retrieved.
Thanks in advance!
JD.

SELECT * FROM BigTable WHERE ROWNUM<=10as a follow up question can you use that for any
other type of query then SELECT? in MySQL forexample
you can use LIMIT on DELETE and UPDATE as well as
SELECT. Not as far as I know.
also another stupid question perhaps but theROWNUM
variable... Is it specific to the query/cursor orthe
table.?It must be used with care. For instance order by
occurs after the limit is applied.
One can use subqueries to get around the above though.thank you for the info... that is quite different then in operation to MySQL LIMIT (which is applied last after ORDER etc.) although that is expected in this case since it's part of the WHERE clause.. i guess that also means that HAVING will happen after as well?

Syntax error in Java persistence language

I wrote this simple program to use Java Persistence Query
public static void main(String[] args) {
test test = new test();
EntityManagerFactory emf = Persistence.createEntityManagerFactory("SVGTopLink");
EntityManager em = emf.createEntityManager();
String sql_text = "SELECT NEW " +
"joinBasicShapes(c.chartName,c.height,c.width,sh.idShape,sh.points,sh.r1,sh.rx,sh.ry,sh.typeName,sh.widthR,sh.x1,sh.x2,sh.y1,sh.y2) "+
"FROM SvgCharts c JOIN BasicShapes sh ON c.id_chart=sh.id_chart WHERE c.id_chart = 1";
Query query = em.createQuery(sql_text);
List lista = query.getResultList();
Iterator it = lista.iterator();
for(int i=0;it.hasNext();it.next()) {
System.out.println("---");
em.close();
emf.close();
But EntityManager doesn't like the query. Do you have any ideea?
Exception in thread "main" java.lang.IllegalArgumentException: An exception occured while creating a query in EntityManager
at oracle.toplink.essentials.internal.ejb.cmp3.EntityManagerImpl.createQuery(EntityManagerImpl.java:194)
at svgtoplink.test.main(test.java:23)
Caused by: Exception TOPLINK-8024 (Oracle TopLink Essentials - 2.0 (Build b41-beta2 (03/30/2007))): oracle.toplink.essentials.exceptions.EJBQLException
Exception Description: Syntax error parsing the query http://SELECT NEW joinBasicShapes(c.chartName,c.height,c.width,sh.idShape,sh.points,sh.r1,sh.rx,sh.ry,sh.typeName,sh.widthR,sh.x1,sh.x2,sh.y1,sh.y2) FROM SvgCharts c JOIN BasicShapes sh ON c.id_chart=sh.id_chart WHERE c.id_chart = 1, line 1, column 177: syntax error at sh.
Internal Exception: line 1:177: expecting DOT, found 'sh'
at oracle.toplink.essentials.exceptions.EJBQLException.syntaxErrorAt(EJBQLException.java:364)
at oracle.toplink.essentials.internal.parsing.ejbql.EJBQLParser.handleANTLRException(EJBQLParser.java:319)
at oracle.toplink.essentials.internal.parsing.ejbql.EJBQLParser.addError(EJBQLParser.java:262)
at oracle.toplink.essentials.internal.parsing.ejbql.EJBQLParser.reportError(EJBQLParser.java:362)
at oracle.toplink.essentials.internal.parsing.ejbql.antlr273.EJBQLParser.joinAssociationPathExpression(EJBQLParser.java:1909)
at oracle.toplink.essentials.internal.parsing.ejbql.antlr273.EJBQLParser.join(EJBQLParser.java:1768)
at oracle.toplink.essentials.internal.parsing.ejbql.antlr273.EJBQLParser.identificationVariableDeclaration(EJBQLParser.java:1629)
at oracle.toplink.essentials.internal.parsing.ejbql.antlr273.EJBQLParser.fromClause(EJBQLParser.java:454)
at oracle.toplink.essentials.internal.parsing.ejbql.antlr273.EJBQLParser.selectStatement(EJBQLParser.java:179)
at oracle.toplink.essentials.internal.parsing.ejbql.antlr273.EJBQLParser.document(EJBQLParser.java:135)
at oracle.toplink.essentials.internal.parsing.ejbql.EJBQLParser.parse(EJBQLParser.java:150)
at oracle.toplink.essentials.internal.parsing.ejbql.EJBQLParser.buildParseTree(EJBQLParser.java:111)
at oracle.toplink.essentials.internal.ejb.cmp3.base.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:200)
at oracle.toplink.essentials.internal.ejb.cmp3.base.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:174)
at oracle.toplink.essentials.internal.ejb.cmp3.base.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:138)
at oracle.toplink.essentials.internal.ejb.cmp3.base.EJBQueryImpl.<init>(EJBQueryImpl.java:99)
at oracle.toplink.essentials.internal.ejb.cmp3.base.EJBQueryImpl.<init>(EJBQueryImpl.java:84)
at oracle.toplink.essentials.internal.ejb.cmp3.EJBQueryImpl.<init>(EJBQueryImpl.java:71)
at oracle.toplink.essentials.internal.ejb.cmp3.EntityManagerImpl.createQuery(EntityManagerImpl.java:189)
... 1 more
Caused by: line 1:177: expecting DOT, found 'sh'
at persistence.antlr.Parser.match(Parser.java:213)
at oracle.toplink.essentials.internal.parsing.ejbql.antlr273.EJBQLParser.joinAssociationPathExpression(EJBQLParser.java:1901)
... 15 more
Process exited with exit code 1.
Can you tel me what means DOT - this is what is supposed to wait - in from clause eg FROM SvgCharts c JOIN BasicShapes sh .
Many thanks,
Aurel

I have these entities ,
public class SvgCharts implements Serializable {
@Id
@Column(name="ID_CHART", nullable = false)
private Long idChart;
@OneToMany(mappedBy = "svgCharts")
private List<BasicShapes> basicShapesList;
public class BasicShapes implements Serializable {
@ManyToOne
@JoinColumn(name = "ID_CHART", referencedColumnName = "ID_CHART")
private SvgCharts svgCharts;
ID_CHART is the PK in svgCharts and FK in basicShapes
I have write this code
String sql_text = "SELECT o FROM SvgCharts charts JOIN charts.ID_CHART shapes WHERE charts.ID_CHART = 1";
Query query = em.createQuery(sql_text);
List lista = query.getResultList();
But I get the following error ;
Exception Description: Error compiling the query [SELECT o FROM SvgCharts charts JOIN charts.ID_CHART shapes WHERE charts.ID_CHART = 1], line 1, column 44: unknown state or association field [ID_CHART] of class [svgtoplink3.SvgCharts].
What do you think? I use JDeveloper 11TP4 for this
Thans in advance,
Aurel

EJB Query Language where condtion based on date

Hi,
I am using EJB3 query language. In the table I have a column called requestdate which is in date time format. I have created an entity class.
I need to select few records using query language(named queries) based on this requestdate matching to the current date. I want to compare only based on Date value (truncating the time). Something like this
select max(o.req_id) from requests o where o.requestdate = :currentdate
currentdate is java.sql.Date value formatted to yyyymmdd only.
How can I do this using query language?
Please help to me get this done.
thanka
Anuradha

Hi Anuradha ,
I'm afraid the query language does not support retrieving the date portion (i.e. truncating the time) from a date field.
I propose you turn you named into a BETWEEN query taking two parameters one for the beginning of the day and another for the end of the day. Then your named query could look like:
SELECT max(o.req_id) FROM requests o WHERE o.requestdate BETWEEN :start AND :end
The following code creates two calendar instances for the current day, one for 00:00:00 and another for 23:59:59:
Calendar start = Calendar.getInstance();
start.set(Calendar.HOUR_OF_DAY, 0);
start.set(Calendar.MINUTE, 0);
start.set(Calendar.SECOND, 0);
start.set(Calendar.MILLISECOND, 0);
Calendar end = Calendar.getInstance();
end.set(Calendar.HOUR_OF_DAY, 23);
end.set(Calendar.MINUTE, 59);
end.set(Calendar.SECOND, 59);
end.set(Calendar.MILLISECOND, 999);
Here is some sample code that creates a query instance for a named query called findMaxRequestPerDay and passes the Date of the above Calendar instance as actual parameter values. It assumes the named query is called findMaxRequestPerDay and the req_id field is a long:
Query query = em.createNamedQuery("findMaxRequestPerDay");
query.setParameter("start", start.getTime());
query.setParameter("end", end.getTime());
Long max = (Long)query.getSingleResult();
I hope this helps.
Regards Michael

JPA query language syntax

My question is if JPA query language syntax allows full qualified class names in the SELECT clause of the query, e.g.:
SELECT * FROM com.abc.Person
This works well with Hibernate, but TopLink Essentials complains about the dots in com.abc.Person.
In the Java EE 5 Tutorial only partially qualified names ( SELECT * FROM Person) are used.
There are only examples with fully qualified names for constants in WHERE clauses.

my first guess:
SELECT t FROM tablename t WHERE t.timestamp>:somethingwhere :something
is handled with something like: (..).setParameter("something", someSQLDate);

Object Query Language (OQL) Support ?

I know Toplink has an "ExpressionBuilder" type querying
But does Toplink support Object Query Language (OQL)
Example :
Something like this ?
// perform query
OQLQuery query = new OQLQuery(
"select x from Person x where x.name = \"Doug Barry\"");
Collection result = (Collection) query.execute();
Iterator iter = result.iterator();
Thanks
Ratheesh

Ratheesh,
TopLink does not support OQL. We offer query support through the following 5 options:
1. EJB QL - for both Entity Beans (CMP/BMP) and Java objects
2. TopLink Expressions - Object based query API
3. SQL calls
4. Stored procedure calls
5. Quey by example
Doug

Applying a query language to collections

Hi, we handed in a project a while ago that was essentially to read in data from a .DAT file, store it in appropriate collections, then use a basic query language to filter through the stored data. I wasn't really happy with my querying though, as it was basically a huge succession of control statements. The queries were of the form "select OBJECTNAME where ATRIBUTE OPERATOR VALUE and ATRIBUTE OPERATOR VALUE", there could be as many sub clauses as desired (0... 200 whatever). For example "select elephant where height > 360 and weight <= 1000".
We had a comment back that we should use a Query interface and a two subclasses to represent a simple query (e.g. height > 360) and then a conjunctive query (ie simplequery1 AND simplequery2 ). The Query interface would then have a match method. I'm struggling to get my head around how I do this, does anyone have a simple example or explaination that might help me out?
Cheers.

I've done something like this a couple times. Your need to get a better idea of what you want your query language to look like. For example, if you're given a list of elephants, the "select elephant" part is unnecessary (your query will just return a list of matching elephants). You should decide if you want it to handle things like (height > (weight / 2)), whether conditions can be nested "((a and b) or (c and d)) and (e or f)". Will you need to support the conditional operator (a ? b : c) or a unary operator (-)? How complex will your order of operations rules be?
If you keep it simple (always two operands), you could go with something like this:
public interface QueryOperator
public boolean eval(Object leftParam, Object rightParam);
public enum BasicOperators implements QueryOperator
public class QueryElement
private QueryOperator operator;
private Object leftParam;
private Object rightParam;
}

XPath Query Language Reference

Aside from the three little examples given in the 11g Guide and the B2B Tech Note #011, is there a reference available for the XPath Query Language used by B2B? Is is possible to use complex XPath queries in the B2B Doc Definitions?

I'm mainly just looking for the full capabilities of the queries.
Specifically, at the moment, I'm looking for a way to match the value of a node to a group of values (like a sql 'in') as well as check the existence and value of other nodes within the same query.
Do the documents I find for 'Preference XPath' pertain here?

EJB query language help!!

Hi all, I have been trying to run a ejb query on JBoss 4.0.5, using built in hypersonic db, For some strange reasons am able to fetch all objects from db without any where clause but if am using a where clause with an attribute name from the entitybean am unable to retrieve any results.
I get an org.hibernate.QueryException, could not resolve property : "property name"
My ejb query looks like this...
SELECT template FROM TemplateSelect template WHERE template.template_name='Template_One'
TemplateSelect is my entity bean class and I do have an attribute named template_name in my bean class.
could any one please suggest me what could be wrong and also direct me to a good tutorial on ejb query language as well as I am fairly new to hibernate and ejb3 !
tons of thanks in advance!
pravin

Hi Anuradha ,
I'm afraid the query language does not support retrieving the date portion (i.e. truncating the time) from a date field.
I propose you turn you named into a BETWEEN query taking two parameters one for the beginning of the day and another for the end of the day. Then your named query could look like:
SELECT max(o.req_id) FROM requests o WHERE o.requestdate BETWEEN :start AND :end
The following code creates two calendar instances for the current day, one for 00:00:00 and another for 23:59:59:
Calendar start = Calendar.getInstance();
start.set(Calendar.HOUR_OF_DAY, 0);
start.set(Calendar.MINUTE, 0);
start.set(Calendar.SECOND, 0);
start.set(Calendar.MILLISECOND, 0);
Calendar end = Calendar.getInstance();
end.set(Calendar.HOUR_OF_DAY, 23);
end.set(Calendar.MINUTE, 59);
end.set(Calendar.SECOND, 59);
end.set(Calendar.MILLISECOND, 999);
Here is some sample code that creates a query instance for a named query called findMaxRequestPerDay and passes the Date of the above Calendar instance as actual parameter values. It assumes the named query is called findMaxRequestPerDay and the req_id field is a long:
Query query = em.createNamedQuery("findMaxRequestPerDay");
query.setParameter("start", start.getTime());
query.setParameter("end", end.getTime());
Long max = (Long)query.getSingleResult();
I hope this helps.
Regards Michael

Limit query for Java Persistence Query Language

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