To validate data I am receiving I need to make sure that the length is not going to exceeded a database column length. Now all the length information is stored in the Hibernate mapping files, is there anyway to access this information programmatically?
You can get to it but it's not easy. You might want to do something like below at startup and store a static cache of the values. There are a lot of special cases to deal with (inheritance, etc), but it should work for simple single-column mappings. I might have left out some instanceof and null checks.
for (Iterator iter=configuration.getClassMappings(); iter.hasNext();) {
PersistentClass persistentClass = (PersistentClass)iter.next();
for (Iterator iter2=persistentClass.getPropertyIterator(); iter2.hasNext();) {
Property property = (Property)iter2.next();
String class = persistentClass.getClassName();
String attribute = property.getName();
int length = ((Column)property.getColumnIterator().next()).getLength();
}
}
Based on Brian's answer, this is what I ended up doing.
private static final Configuration configuration = new Configuration().configure();
public static int getColumnLength(String className, String propertyName) {
PersistentClass persistentClass = configuration.getClassMapping(className);
Property property = persistentClass.getProperty(propertyName);
int length = ((Column) property.getColumnIterator().next()).getLength();
return length;
}
This appears to be working well. Hope this is helpful to anyone who stumbles upon this question.
My preferred development pattern is to base the column length on a constant, which can be easily referenced:
class MyEntity {
public static final int MY_FIELD_LENGTH = 500;
#Column(length = MY_FIELD_LENGTH)
String myField;
...
}
Sometimes it may be problem to get the Configuration object (if you are using some application framework and you are not creating session factory by yourself using the Configuration).
If you are using for example Spring, you can use the LocalSessionFactoryBean (from your applicationContext) to obtain Configuration object. Then obtaining of column length is just piece of cake ;)
factoryBean.getConfiguration().getClassMapping(String entityName) .getTable().getColumn(Column col).getLength()
However, when I try to access the LocalSessionFactoryBean, I take a class cast exception
LocalSessionFactoryBean factoryBean = (LocalSessionFactoryBean) WebHelper.instance().getBean("sessionFactory");
exception:
org.hibernate.impl.SessionFactoryImpl cannot be cast to org.springframework.orm.hibernate3.LocalSessionFactoryBean
<bean id="sessionFactory"
class="org.springframework.orm.hibernate3.LocalSessionFactoryBean>
This seems devious....
EDIT: found the answer. You need to use an ampersand in front of the bean name string
LocalSessionFactoryBean factoryBean = (LocalSessionFactoryBean) WebHelper.instance().getBean("&sessionFactory");
see this Spring forum post
Related
I need to dynamically assign values of cacheResolver for #Cacheable in runtime because cacheResolver has the same value for #Cacheable in every method. Hence, I use Spring AOP to dynamically assign the value but then Spring does not recognize the newly added value for cacheResolver.
Seems that AOP load #Cacheable value at the beginning.
Anyone knows how to make it work?
My AOP code:
#Aspect
#Component
#Order(1)
public class CacheableAspect {
#Pointcut("#annotation(org.springframework.cache.annotation.Cacheable)")
public void cacheablePointCut() {}
#Before("cacheablePointCut()")
public void addCacheableResolver(JoinPoint joinPoint) {
Annotation cacheableAnnotation = getCacheableAnnotation(joinPoint);
Object handler = Proxy.getInvocationHandler(cacheableAnnotation);
Field f;
try {
f = handler.getClass().getDeclaredField("memberValues");
} catch (NoSuchFieldException | SecurityException e) {
throw new IllegalStateException(e);
}
f.setAccessible(true);
Map<String, Object> memberValues;
try {
memberValues = (Map<String, Object>) f.get(handler);
} catch (IllegalArgumentException | IllegalAccessException e) {
throw new IllegalStateException(e);
}
memberValues.put("cacheResolver", "cacheableResolver");
}
private Annotation getCacheableAnnotation(JoinPoint joinPoint) {
MethodSignature signature = (MethodSignature) joinPoint.getSignature();
Method method = signature.getMethod();
return method.getAnnotation(Cacheable.class);
}
}
My #Cacheable code in which i want cacheResolver is dynamically assigned a value:
#Cacheable(value = "test")
public int test() {
System.out.println("xxx");
return 10;
}
OK, so you are trying to dynamically change an annotation representation in the JVM during runtime. Not only is that ugly, but it probably does not work as you hope it would. It seems you found out that specific annotations are represented by a dynamic proxy instance during runtime, then you are successfully manipulating one of its field values. But annotations are meant to be immutable, aber depending on when e.g. Spring scans the annotations while wiring the application, your approach to modify the proxy fields later, while being a nice try, just comes too late.
How about a more canonical approach to use multiple cache managers and/or a resolver which dynamically does what you need to begin with? As much as I love AOP, it is not the answer to everyhing.
By the way, even though your aspect is kind of useless in this case, at least we can use it as an example of how to bind annotation values to advice methods parameters, i.e. you do not need to fetch the annotation from the method by reflection next time you write an aspect:
#Pointcut("#annotation(cacheable)")
public void cacheablePointCut(Cacheable cacheable) {}
#Before("cacheablePointCut(cacheable)")
public void addCacheableResolver(JoinPoint joinPoint, Cacheable cacheable) {
Object handler = Proxy.getInvocationHandler(cacheable);
// (...)
}
I have a table which contains a column of type: integer[]
I'm trying to map my entity to this table and I've tried the following suggestion of:
#ElementCollection
private ArrayList<Integer> col;
public MyEntity() {
col = new ArrayList<>();
}
However I get the following error: Illegal attempt to map a non collection as a #OneToMany, #ManyToMany or #CollectionOfElements
Not sure how to get around this. I'm open to changing the entity's datatype, but I would prefer not to move this property into its own table/entity. Is there another solution? Thanks.
The field must be of type List<Integer>, not ArrayList<Integer>.
The JPA engine must be able to use its own List implementation, used for lazy-loading, dirty checking, etc.
It's a good idea in general to program on interfaces rather than implementations, and it's a requirement to do it in JPA entities.
I have recently started evaluating Dapper as a potential replacement for EF, since I was not too pleased with the SQL that was being generated and wanted more control over it. I have a question regarding mapping a complex object in my domain model. Let's say I have an object called Provider, Provider can contain several properties of type IEnumerable that should only be accessed by going through the parent provider object (i.e. aggregate root). I have seen similar posts that have explained using the QueryMultiple and a Map extension method but was wondering how if I wanted to write a method that would bring back the entire object graph eager loaded, if Dapper would be able to do this in one fell swoop or if it needed to be done piece-meal. As an example lets say that my object looked something like the following:
public AggregateRoot
{
public int Id {get;set;}
...//simple properties
public IEnumerable<Foo> Foos
public IEnumerable<Bar> Bars
public IEnumerable<FooBar> FooBars
public SomeOtherEntity Entity
...
}
Is there a straightforward way of populating the entire object graph using Dapper?
I have a similar situation. I made my sql return flat, so that all the sub objects come back. Then I use the Query<> to map the full set. I'm not sure how big your sets are.
So something like this:
var cnn = sqlconnection();
var results = cnn.Query<AggregateRoot,Foo,Bars,FooBar,someOtherEntity,AggregateRoot>("sqlsomething"
(ar,f,b,fb,soe)=>{
ar.Foo = f;
ar.Bars = b;
ar.FooBar = fb;
ar.someotherentity = soe;
return ar;
},.....,spliton:"").FirstOrDefault();
So the last object in the Query tag is the return object. For the SplitOn, you have to think of the return as a flat array that the mapping will run though. You would pick the first return value for each new object so that the new mapping would start there.
example:
select ID,fooid, foo1,foo2,BarName,barsomething,foobarid foobaritem1,foobaritem2 from blah
The spliton would be "ID,fooid,BarName,foobarid". As it ran over the return set, it will map the properties that it can find in each object.
I hope that this helps, and that your return set is not too big to return flat.
I'm pretty new to JPA/JDO and the whole objectdb world.
I have an entity with a set of strings, looks a bit like:
#Entity
public class Foo{
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
private Key id;
private Set<String> bars;
public void setBars(Set<String> newBars){
if(this.bars == null)
this.bars = new HashSet<String>;
this.bars = newBars;
}
public Set<String> getBars(){
return this.bars;
}
public void addBar(String bar){
if(this.bars == null)
this.bars = new HashSet<String>;
this.bars.add(bar);
}
}
Now, in another part of the code, I'm trying to do something like this:
EntityManager em = EMF.get().createEntityManager();
Foo myFoo = em.find(Foo.class, fooKey);
em.getTransaction().begin();
myFoo.addBar(newBar);
em.merge(myFoo);
em.getTransaction().commit();
When, of course, newBar is a String.
But, what I get is:
javax.jdo.JDODetachedFieldAccessException: You have just attempted to access field "bars" yet this field was not detached when you detached the object. Either dont access this field, or detach it when detaching the object.
I've searched for an answer, but I couldn't find one.
I've seen someone ask about a Set of strings, and he was told to add an #ElementCollection notation.
I tried that, but I got an error about the String class Metadata (I don't really understand what it means.)
I would really appreciate some help on this thing, even a good reference to someone explaining this (in simple English).
OK,
So I found the answer in some blog.
So for anyone who's interested:
In order to use a Collection of simple data types (in JPA), a
#Basic
notation should be added to the collection. So from my example at the top, It should've been written:
#Basic
private Set<String> bars;
So you are using JPA, right? (I see EntityManager rather than JDO's PersistenceManager.) Since you are getting a JDO error, I suspect that your app isn't configured properly for JPA.
JPA docs: http://code.google.com/appengine/docs/java/datastore/jpa/overview.html
JDO docs: http://code.google.com/appengine/docs/java/datastore/jdo/overview.html
You need to pick one datastore wrapper and stick with it. The default new app with the Eclipse tools is configured for JDO, and it is a reasonable choice, but you'll have to change your annotations around a little bit.
Following grails domain class:
class MyClass {
Map myMap
}
Now for myMap, grails automatically creates a new table for the elements in the map. However if I add elements which are too long (e.g. 1024 characters), I get a DB error.
Can I somehow tell grails to make the respective column in myMap's table big enough to allow for larger Strings, or do I have to do this manually in the DB?
I already tried
static constraints = {
myMap(maxSize:1024)
}
which doesn't work (as expected because maxSize should refer to the Map's values and not to the Map itself).
If not via constraints, maybe there's a way to do it via
static mapping { ... }
?
An alternative approach I used successfully was to push the map out into a collection of a collaborator domain class.
class DynaProperty {
String name
String value
static belongsTo = MyClass
static constraints = {
value(maxSize:4000) //Or whatever number is appropriate
}
}
And then in MyClass:
class MyClass {
static hasMany = [dynaProperties:DynaProperty]
}
This is almost a map, and it gives you the ability to use dynamic finders to pull up an individual entry.
what are you trying to accomplish? Is there always the same number of things in the map? If there is you should define those properties on your class.
You can see the problem with your current approach -- there is no way to figure out what might be in the map until runtime, so how can grails possibly create a columns for it? Im surprised it even worked to begin with...