Using Play! framework and it's JPASupport class I have run into a problem with a legacy database.
I have the following class:
#Entity
#Table(name="product_catalog")
public class ProductCatalog extends JPASupport {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
public Integer product_catalog;
#OneToOne
#JoinColumn(name="upper_catalog")
public ProductCatalog upper_catalog;
public String name;
}
Some product catalogs don't have an upper catalog, and this is referenced as 0 in a legacy database. If I supply the upper_catalog as NULL, then expectedly JPA inserts a NULL value to that database column.
How could I force the null values to be 0 when writing to the database and the other way around when reading from the database?
I don't see any easy way of achieving what you want with JPA directly (and there are great chance that even if you find a way that works with basic operation like save or load, that it will not work with more complex use case, like complex criteria / hql, none standard fetching mode, etc)
So i would do that :
#Entity
#Table(name="product_catalog")
public class ProductCatalog extends JPASupport {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
public Integer product_catalog;
#Column(name="upper_catalog")
public Long upper_catalog_id;
public String name;
public ProductCatalog getUpperCatalog() {
if (upper_catalog_id == 0)
return null;
return ProductCatalog.findById(upper_catalog_id);
}
public void setUpperCatalog(ProductCatalog pc) {
if (pc == null) {
upper_catalog_id = 0;
}
else {
if (pc.id == null) {
// option 1. a bit like a cascade
pc.save();
// option 2. if you consider passing a transient entity is not valid
throw new RuntimeException("transient entity " + pc.toString());
}
upper_catalog_id = pc.id;
}
}
}
I see two options:
Use a primitive data type as Id (i.e. int instead of Integer)
If you are using Hibernate as JPA provider, use a CustomType to do the conversion
Related
I am developing an App in Xamarin type PCL, for my DB structure, I want to use SQLite, but I have the following doubts ...
When entering a record in my DB, it takes the ID = 0, in my data model use
[PrimaryKey, AutoIncrement]
Public int ViolationID {get; set; }
And still, I enter the registry at zero, I do not know I'm doing wrong ... or is this a bug in the SQLite.NET-PCL package?
How can I verify that these records are actually being entered? I have in my code
public class DataAccess : IDisposable
{
private SQLiteConnection connection;
public DataAccess()
{
var entity = DependencyService.Get<IEntity>();
connection = new SQLiteConnection(entity.Plataforma, System.IO.Path.Combine(entity.DirectorioBD, "Infraccions.db3"));
connection.CreateTable<Infraccion>();
}
public void InsertInfraccion(Infraccion infraccion)
{
connection.Insert(infraccion);
}
public void UpdateInfraccion(Infraccion infraccion)
{
connection.Update(infraccion);
}
public Infraccion GetInfraccion(int InfraccionID)
{
return connection.Table<Infraccion>().FirstOrDefault(c => c.InfraccionID == InfraccionID);
}
public List<Infraccion> GetInfraccions()
{
return connection.Table<Infraccion>().OrderBy(c => c.MotivoID).ToList();
}
public void DeleteInfraccion(Infraccion infraccion)
{
connection.Delete(infraccion);
}
public void Dispose()
{
connection.Dispose();
}
}
Should I create a table called Infraccions.db3 on my phone?
Thank you for your comments...
Are you saying that all new records have an ID of 0 and overwrite the existing record in the database?
If so, then this is how SQLite works - for int columns 0 is a valid value, so when the ID is 0 it will overwrite the record, instead of incrementing the value.
The correct way to use int primary keys is to define your primary key as a nullable int, that way the value for a new record is null, which will be updated to the next available id:
[PrimaryKey, AutoIncrement]
public int? ViolationID {get; set; }
Essentially change int to int?.
1) When entering a record in my DB, it takes the ID = 0, in my data
model use
You are using primary key and auto increment in your model that's means you are not able to enter 0 manually in the primary field and it takes automatically next value in this field.
2) How can I verify that these records are actually being entered?
You can get DB file path when you create your database and you can able to open and see that data.
(System.IO.Path.Combine(entity.DirectorioBD, "Infraccions.db3") )
There are many browser plugins to access the sqllite database.
I don't know why I received the error :
org.apache.cayenne.CayenneRuntimeException: [v.4.0.M5 Feb 24 2017 07:47:55] Commit Exception
[...]
Caused by: java.sql.SQLException: Procédure stockée 'auto_pk_for_table' introuvable.
[...]
I'm using Cayenne :
<dependency>
<groupId>org.apache.cayenne</groupId>
<artifactId>cayenne-server</artifactId>
<version>4.0.M5</version>
</dependency>
and JDTS for sql server :
<dependency>
<groupId>net.sourceforge.jtds</groupId>
<artifactId>jtds</artifactId>
<version>1.3.1</version>
</dependency>
The connexion is ok :
avr. 10, 2017 2:36:30 PM org.apache.cayenne.datasource.DriverDataSource getConnection
INFOS: +++ Connecting: SUCCESS.
I'm trying to create a new user (I'm starting by bascis!) so my code is :
(I cut a little bit, it's too long:!)
public abstract class _UserInfo extends CayenneDataObject {
public static final String ADDRESS_PROPERTY = "address";
public void setAddress(String address) {
writeProperty(ADDRESS_PROPERTY, address);
}
public String getAddress() {
return (String)readProperty(ADDRESS_PROPERTY);
}
}
public class UserInfo extends _UserInfo implements Serializable {
private static final long serialVersionUID = 1L;
public String address;
public String getAdress() {
return address;
}
public void setAddress(String address) {
super.setAddress(address);
}
//I have the hashcode and equals too
}
Then, I used vaadin to create my form :
public class UserAddView extends CustomComponent implements View {
private static final long serialVersionUID = 1L;
private TextField address;
private Button save;
public static final String USERVIEW = "user";
public boolean checkValidation() {
if (!checkTextFieldValid(address))
return false;
return true;
}
public boolean checkTextFieldValid(TextField element) {
if (element == null || element.isEmpty()) {
Notification.show(
"You should register a " + element.getDescription(),
Type.WARNING_MESSAGE);
return false;
}
return true;
}
public UserAddView() {
VerticalLayout mainLayout = new VerticalLayout();
mainLayout.setSizeFull();
setCompositionRoot(mainLayout);
final VerticalLayout vlayout = new VerticalLayout();
address = new TextField("Address:");
address.setDescription("Address");
vlayout.addComponent(address);
save = new Button("Save");
vlayout.addComponent(save);
mainLayout.addComponent(new HeaderMenu());
mainLayout.addComponent(vlayout);
addListeners();
}
private void addListeners() {
save.addClickListener(new ClickListener() {
private static final long serialVersionUID = 1L;
#Override
public void buttonClick(ClickEvent event) {
if (checkValidation() == true) {
ServerRuntime cayenneRuntime = ServerRuntime.builder()
.addConfig("cayenne-myapplication.xml").build();
ObjectContext context = cayenneRuntime.newContext();
UserInfo user = context.newObject(UserInfo.class);
user.setAddress(address.getValue());
user.getObjectContext().commitChanges();
Notification.show(
"Has been saved, We will send you your password by email. Your user login is: "
+ email.getValue(), Type.TRAY_NOTIFICATION);
getUI().getNavigator().navigateTo(HomepageView.MAINVIEW);
}
}
});
}
#Override
public void enter(ViewChangeEvent event) {
// TODO Auto-generated method stub
}
}
EDIT, add information : In my user object, I have a userid (primary key), in cayenne I wrote it as primary key too and in smallint. This error seems to be link... https://cayenne.apache.org/docs/3.1/api/org/apache/cayenne/dba/sybase/SybasePkGenerator.html
The error happens when you insert a new object. For each new object Cayenne needs to generate a value of the primary key. There are various strategies to do this. The default strategy depends on the DB that you are using. For SQLServer (and for Sybase, as you've discovered :)) that strategy is to use a special stored procedure.
To create this stored procedure (and other supporting DB objects), go to CayenneModeler, open your project, and select "Tools > Generate Database Schema". In "SQL Options" tab, uncheck all checkboxes except for "Create Primary Key Support". The SQL you will see in the window below the checkboxes is what you need to run on SQL server. Either do it from Cayenne modeler or copy/paste to your favorite DB management tool.
There's also an alternative that does not require a stored procedure - using DB auto-increment feature. For this you will need to go to each DbEntity in the Modeler and under the "Entity" tab select "Database-Generated" in the "Pk Generation Strategy" dropdown. This of course implies that your PK column is indeed an auto-increment in the DB (meaning you may need to adjust your DB schema accordingly).
Given the following:
public class SomePoco {
public int IntValue { get; }
}
and
CREATE TABLE SomePocoStorage (IntValue INT NOT NULL)
and
INSERT SomePocoStorage VALUES (1), (274)
If I call
connection.Query<SomePoco>("SELECT * FROM SomePocoStorage")
does Dapper handle populating the IntValue field on the returned SomePoco instances?
Good question! It isn't a scenario I've targeted, but I'd be more than happy to take a look at what would be involved. Since we already do a lot of nasty reflection, this could still be viable. Probably better as a github issue, but I'll have a look.
Update - it does now (at the current time, via repo only - not deployed):
[Fact] // passes
public void GetOnlyProperties()
{
var obj = connection.QuerySingle<HazGetOnly>(
"select 42 as [Id], 'def' as [Name];");
obj.Id.IsEqualTo(42);
obj.Name.IsEqualTo("def");
}
class HazGetOnly
{
public int Id { get; }
public string Name { get; } = "abc";
}
No because there's no way for Dapper to set the value of the property if that property only has a getter.
My application is using SQLServer and JPA2 in the backend. App makes use of a timestamp column (in the SQLServer sense, which is equivalent to row version see here) per entity to keep track of freshly modified entities. NB SQLServer stores this column as binary(8).
Each entity has a respective timestamp property, mapped as #Lob, which is the way to go for binary columns:
#Lob
#Column(columnDefinition="timestamp", insertable=false, updatable=false)
public byte[] getTimestamp() {
...
The server sends incremental updates to mobile clients along with the latest database timestamp. The mobile client will then pass the old timestamp back to the server on the next refresh request so that the server knows to return only fresh data. Here's what a typical query (in JPQL) looks like:
select v from Visit v where v.timestamp > :oldTimestamp
Please note that I'm using a byte array as a query parameter and it works fine when implemented in JPQL this way.
My problems begin when trying to do the same using the Criteria API:
private void getFreshVisits(byte[] oldVersion) {
EntityManager em = getEntityManager();
CriteriaQuery<Visit> cq = cb.createQuery(Visit.class);
Root<Visit> root = cq.from(Visit.class);
Predicate tsPred = cb.gt(root.get("timestamp").as(byte[].class), oldVersion); // compiler error
cq.where(tsPred);
...
}
The above will result in compiler error as it requires that the gt method used strictly with Number. One could instead use the greaterThan method which simply requires the params to be Comparable and that would result in yet another compiler error.
So to sum it up, my question is: how can I use the criteria api to add a greaterThan predicate for a byte[] property? Any help will be greatly appreciated.
PS. As to why I'm not using a regular DateTime last_modified column: because of concurrency and the way synchronization is implemented, this approach could result in lost updates. Microsoft's Sync Framework documentation recommends the former approach as well.
I know this was asked a couple of years back but just in case anyone else stumbles upon this.. In order to use a SQLServer rowver column within JPA you need to do a couple of things..
Create a type that will wrap the rowver/timestamp:
import com.fasterxml.jackson.annotation.JsonIgnore;
import javax.xml.bind.annotation.XmlTransient;
import java.io.Serializable;
import java.math.BigInteger;
import java.util.Arrays;
/**
* A RowVersion object
*/
public class RowVersion implements Serializable, Comparable<RowVersion> {
#XmlTransient
#JsonIgnore
private byte[] rowver;
public RowVersion() {
}
public RowVersion(byte[] internal) {
this.rowver = internal;
}
#XmlTransient
#JsonIgnore
public byte[] getRowver() {
return rowver;
}
public void setRowver(byte[] rowver) {
this.rowver = rowver;
}
#Override
public int compareTo(RowVersion o) {
return new BigInteger(1, rowver).compareTo(new BigInteger(1, o.getRowver()));
}
#Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
RowVersion that = (RowVersion) o;
return Arrays.equals(rowver, that.rowver);
}
#Override
public int hashCode() {
return Arrays.hashCode(rowver);
}
}
The key here is that it implement Comparable if you want to use it in calculations (which you definitely do)..
Next create a AttributeConverter that will move from a byte[] to the class you just made:
import javax.persistence.AttributeConverter;
import javax.persistence.Converter;
/**
* JPA converter for the RowVersion type
*/
#Converter
public class RowVersionTypeConverter implements AttributeConverter<RowVersion, byte[]> {
#Override
public byte[] convertToDatabaseColumn(RowVersion attribute) {
return attribute != null ? attribute.getRowver() : null;
}
#Override
public RowVersion convertToEntityAttribute(byte[] dbData) {
return new RowVersion(dbData);
}
}
Now let's apply this RowVersion attribute/type to a real world scenario. Let's say you wanted to find all Programs that have changed on or before some point in time.
One straightforward way to solve this would be to use a DateTime field in the object and timestamp column within db. Then you would use 'where lastUpdatedDate <= :date'.
Suppose that you don't have that timestamp column or there's no guarantee that it will be updated properly when changes are made; or let's say your shop loves SQLServer and wants to use rowver instead.
What to do? There are two issues to solve.. one how to generate a rowver and two is how to use the generated rowver to find Programs.
Since the database generates the rowver, you can either ask the db for the 'current max rowver' (a custom sql server thing) or you can simply save an object that has a RowVersion attribute and then use that object's generated RowVersion as the boundary for the query to find the Programs changed after that time. The latter solution is more portable is what the solution is below.
The SyncPoint class snippet below is the object that is used as a 'point in time' kind of deal. So once a SyncPoint is saved, the RowVersion attached to it is the db version at the time it was saved.
Here is the SyncPoint snippet. Notice the annotation to specify the custom converter (don't forget to make the column insertable = false, updateable = false):
/**
* A sample super class that uses RowVersion
*/
#MappedSuperclass
public abstract class SyncPoint {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
// type is rowver for SQLServer, blob(8) for postgresql and h2
#Column(name = "current_database_version", insertable = false, updatable = false)
#Convert(converter = RowVersionTypeConverter.class)
private RowVersion currentDatabaseVersion;
#Column(name = "created_date_utc", columnDefinition = "timestamp", nullable = false)
private DateTime createdDate;
...
Also (for this example) here is the Program object we want to find:
#Entity
#Table(name = "program_table")
public class Program {
#Id
private Integer id;
private boolean active;
// type is rowver for SQLServer, blob(8) for postgresql and h2
#Column(name = "rowver", insertable = false, updatable = false)
#Convert(converter = RowVersionTypeConverter.class)
private RowVersion currentDatabaseVersion;
#Column(name = "last_chng_dt")
private DateTime lastUpdatedDate;
...
Now you can use these fields within your JPA criteria queries just like anything else.. here is a snippet that we used inside a spring-data Specifications class:
/**
* Find Programs changed after a synchronization point
*
* #param filter that has the changedAfter sync point
* #return a specification or null
*/
public Specification<Program> changedBeforeOrEqualTo(final ProgramSearchFilter filter) {
return new Specification<Program>() {
#Override
public Predicate toPredicate(Root<Program> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
if (filter != null && filter.changedAfter() != null) {
// load the SyncPoint from the db to get the rowver column populated
SyncPoint fromDb = synchronizationPersistence.reload(filter.changedBeforeOrEqualTo());
if (fromDb != null) {
// real sync point made by database
if (fromDb.getCurrentDatabaseVersion() != null) {
// use binary version
return cb.lessThanOrEqualTo(root.get(Program_.currentDatabaseVersion),
fromDb.getCurrentDatabaseVersion());
} else if (fromDb.getCreatedDate() != null) {
// use timestamp instead of binary version cause db doesn't make one
return cb.lessThanOrEqualTo(root.get(Program_.lastUpdatedDate),
fromDb.getCreatedDate());
}
}
}
return null;
}
};
}
The specification above works with both the binary current database version or a timestamp.. this way I could test my stuff and all the upstream code on a database other than SQLServer.
That's it really: a) type to wrap the byte[] b) JPA converter c) use attribute in query.
I don't know why I can't persistent MAP in JPA in GAE
AnnualReport thatyear = .......
if (stud.getAnnualReport() == null){
Map<Integer,AnnualReport> temp = new HashMap<Integer,AnnualReport>();
temp.put(thatyear.getAttrKey(), thatyear);
stud.setAnnualReport(temp);
} else{
Map<Integer,AnnualReport> temp2 = stud.getAnnualReport();
temp2.put(thatyear.getAttrKey(), thatyear);
stud.setAnnualReport(temp2);
}
em.getTransaction().begin();
try {
em.persist(stud);
em.getTransaction().commit();
} finally {
if (em.getTransaction().isActive()) {
em.getTransaction().rollback();
}
}
Actually in http:// localhost :8888/_ah/admin/datastore I can see the thatyear has been persistent; However, I can never get them; or, stud.getAnnualReport() is always empty.
EntityManager em;
em = EMF.get().createEntityManager();
AnnualReport thatyear = stud.getAnnualReport().get(yearselected);
I really don't know what to do. Following is the relationship between Stud & AnnualReport
Stud
#Entity( name = "Stud")
public class Stud{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Key studID;
private String lastName = new String();
private Map<Integer,AnnualReport>annualReport = new HashMap<Integer,AnnualReport>(20);
#OneToMany(mappedBy="stud",cascade = CascadeType.ALL)
#MapKey(name = "attrKey")
#Basic
public Map<Integer, AnnualReport> getAnnualReport() {
return annualReport;
}
AnnualReport
#Entity( name = "AnnualReport")
public class AnnualReport implements Serializable{
private static final long serialVersionUID = 3581307841164176872L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Key annualReportID;
public int attrKey;
#ManyToOne
Stud stud;
private String attendSchoolNote;
I don't know what happens. Why I can't get those map information which are already persistent?
No idea why you don't get the expected result, but then you present no debug info. You can easily follow the persistence process using the log, telling you what is actually persisted into the GAE Entity objects. GAE has a (JDO) unit test at
http://code.google.com/p/datanucleus-appengine/source/browse/trunk/tests/com/google/appengine/datanucleus/jdo/JDOMapTest.java
which demonstrates correct behaviour (and since JDO/JPA is simply a wrapper over the persistence engine, no reason to think the same would not persist fine using JPA).
Edit : in fact I just added a test for JPA maps at http://code.google.com/p/datanucleus-appengine/source/browse/trunk/tests/com/google/appengine/datanucleus/jpa/JPAMapTest.java and works fine.