We Keep Coding

How to Enforce MyBatis PSQL custom TypeHandler on property level

I am using a DTO which contains Set<UUID> and Set<String>.
public class MyBatisDTO implements Serializable{
// other attributes
private Set<UUID> uuidSet;
private Set<String> stringSet;
.....
}
A typeHandler has already been registered for Generic-Type Set<T>.
#MappedJdbcTypes(JdbcType.OTHER)
#MappedTypes(Set.class)
public class SetTypeHandler extends BaseTypeHandler<Set<T>> {
#Override
public Set<T> getNullableResult(ResultSet rs, String columnName) throws SQLException {
return mapFromJson(rs.getString(columnName));
}
.......
Now the problem is that when above mentioned MyBatisDTO.java is being mapped from DB values where both columns uuidSet and stringset are stored as jsonb values, typeHandler picks the Generic type as String -> T extends String for Set<UUID> uuidSet; as well which is leading to auto-type conversion to all items of uuidSet as String. This is not an error but in debugging it can be seen that uuidSet contains String values.
Later on, which also leads in de-serialization of JAX-RS response but thats another topic which is not important at the moment.
My question is Is there a way that we can enforce a typeHandler on property's level? so I am looking for a solution in which I may attach custom TypeHandler on property level, something like this
//SUDO_CODE
public class MyBatisDTO implements Serializable{
// other attributes
#TypeHandler ("com.mybatis.handlers.typeHandler.SetUUIDTypeHandler")
private Set<UUID> uuidSet;
#TypeHandler ("com.mybatis.handlers.typeHandler.SetStringTypeHandler")
private Set<String> stringSet;
.....
}
OR if there is a way to mention these typeHandlers on Mapper-Level, something like this?
#Mapper
public interface MyBatisMapper {
//TYPE HANDLER ATTACHMENT/CONFIGURATION HERE ..???
#Select("SELECT uuidSet, stringSet FROM MyBatisDTO WHERE param = #{param}")
Cursor<MyBatisDTO> getData(#Param("param") final UUID param);
.....
}

You can do it with a result map:
#Mapper
public interface MyBatisMapper {
#Select("SELECT uuidSet, stringSet FROM MyBatisDTO WHERE param = #{param}")
#Results({
#Result(column = "uuidSet", property="uuidSet", typeHandler = "com.mybatis.handlers.typeHandler.SetUUIDTypeHandler"),
#Result(column = "stringSet", property="stringSet", typeHandler = "com.mybatis.handlers.typeHandler.SetStringTypeHandler")
})
Cursor<MyBatisDTO> getData(#Param("param") final UUID param);
}

Mybatis problem - convey parameter to my TypeHandler class through MyObjectFactory

I have class TypeHandler that works normal. But now i need to convey parametr - DB schema inside TypeHandler. I dont need to use this DB schema parametr as result, so i dont map it in mybatis-config.xml
Schema parametr used in CallableStatement in ClobTypeHandler.
public class ClobTypeHandler extends BaseTypeHandler<String> {
public String scheme;
public ClobTypeHandler(String scheme) {
this.scheme = scheme;
}
public ClobTypeHandler() {
}
I've created my object factory:
public class ComponentObjectFactory extends DefaultObjectFactory {
String scheme;
public ComponentObjectFactory() {
}
public void setScheme(String scheme) {
this.scheme = scheme;
}
public <T> T create(Class<T> type) {
System.out.println("create:" + type);
return super.create(type);
}
public <T> T create(Class<T> type, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
if (type.equals(ClobTypeHandler.class)) {
String scheme = (String)constructorArgs.get(0);
ClobTypeHandler cth = (ClobTypeHandler)super.create(type, constructorArgTypes, constructorArgs);
cth.scheme = scheme;
return cth;
} else {
return super.create(type, constructorArgTypes, constructorArgs);
}
}
}
And registered it in mybatis-config:
<typeHandlers>
<typeHandler javaType="java.lang.String"
jdbcType="CLOB"
handler="model.DB.ClobTypeHandler"/>
</typeHandlers>
<objectFactory type="services.ComponentObjectFactory">
<property name="name" value="ComponentObjectFactory"/>
</objectFactory>
But when myBatis creates an instance of ClobTypeHandler - it not uses my ComponentObjectFactory and even don't come to DefaultObjectFactory. I set breakpoints in constructors there and see it. As result when debug comes to ClobTypeHandler - it s another instance, not my, that i created as
ComponentObjectFactory cof = new ComponentObjectFactory();
cof.create(ClobTypeHandler.class, Arrays.asList(String.class), Arrays.asList(this.scheme));
How to force myBatis use my instance of ClobTypeHandler ?
How to force myBatis use my ComponentObjectFactory ?
How to force myBatis use only parameter constructor to convey schema parametr there ?

reactive repository throws exception when saving a new object

I am using r2dbc, r2dbc-h2 and experimental spring-boot-starter-data-r2dbc
implementation 'org.springframework.boot.experimental:spring-boot-starter-data-r2dbc:0.1.0.M1'
implementation 'org.springframework.data:spring-data-r2dbc:1.0.0.RELEASE' // starter-data provides old version
implementation 'io.r2dbc:r2dbc-h2:0.8.0.RELEASE'
implementation 'io.r2dbc:r2dbc-pool:0.8.0.RELEASE'
I have created reactive repositories
public interface IJsonComparisonRepository extends ReactiveCrudRepository<JsonComparisonResult, String> {}
Also added a custom script that creates a table in H2 on startup
#SpringBootApplication
public class JsonComparisonApplication {
public static void main(String[] args) {
SpringApplication.run(JsonComparisonApplication.class, args);
}
#Bean
public CommandLineRunner startup(DatabaseClient client) {
return (args) -> client
.execute(() -> {
var resource = new ClassPathResource("ddl/script.sql");
try (var is = new InputStreamReader(resource.getInputStream())) {
return FileCopyUtils.copyToString(is);
} catch (IOException e) {
throw new RuntimeException(e);
} })
.then()
.block();
}
}
My r2dbc configuration looks like this
#Configuration
#EnableR2dbcRepositories
public class R2dbcConfiguration extends AbstractR2dbcConfiguration {
#Override
public ConnectionFactory connectionFactory() {
return new H2ConnectionFactory(
H2ConnectionConfiguration.builder()
.url("mem:testdb;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE")
.username("sa")
.build());
}
}
My service where I perform the logic looks like this
#Override
public Mono<JsonComparisonResult> updateOrCreateRightSide(String comparisonId, String json) {
return updateComparisonSide(comparisonId, storedComparisonResult -> {
storedComparisonResult.setRightSide(json);
return storedComparisonResult;
});
}
private Mono<JsonComparisonResult> updateComparisonSide(String comparisonId,
Function<JsonComparisonResult, JsonComparisonResult> updateSide) {
return repository.findById(comparisonId)
.defaultIfEmpty(createResult(comparisonId))
.filter(result -> ComparisonDecision.NONE == result.getDecision()) // if not NONE - it means it was found and completed
.switchIfEmpty(Mono.error(new NotUpdatableCompleteComparisonException(comparisonId)))
.map(updateSide)
.flatMap(repository::save);
}
private JsonComparisonResult createResult(String comparisonId) {
LOGGER.info("Creating new comparison result: {}.", comparisonId);
var newResult = new JsonComparisonResult();
newResult.setDecision(ComparisonDecision.NONE);
newResult.setComparisonId(comparisonId);
return newResult;
}
The domain looks like this
#Table("json_comparison")
public class JsonComparisonResult {
#Column("comparison_id")
#Id
private String comparisonId;
#Column("left")
private String leftSide;
#Column("right")
private String rightSide;
// #Enumerated(EnumType.STRING) - no support for now
#Column("decision")
private ComparisonDecision decision;
private String differences;
The problem is that when I try to add any object to the database it fails with the exception
org.springframework.dao.TransientDataAccessResourceException: Failed to update table [json_comparison]. Row with Id [4] does not exist.
at org.springframework.data.r2dbc.repository.support.SimpleR2dbcRepository.lambda$save$0(SimpleR2dbcRepository.java:91) ~[spring-data-r2dbc-1.0.0.RELEASE.jar:1.0.0.RELEASE]
at reactor.core.publisher.FluxHandle$HandleSubscriber.onNext(FluxHandle.java:96) ~[reactor-core-3.3.1.RELEASE.jar:3.3.1.RELEASE]
at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onNext(FluxOnErrorResume.java:73) ~[reactor-core-3.3.1.RELEASE.jar:3.3.1.RELEASE]
at reactor.core.publisher.MonoUsingWhen$MonoUsingWhenSubscriber.deferredComplete(MonoUsingWhen.java:276) ~[reactor-core-3.3.1.RELEASE.jar:3.3.1.RELEASE]
at reactor.core.publisher.FluxUsingWhen$CommitInner.onComplete(FluxUsingWhen.java:536) ~[reactor-core-3.3.1.RELEASE.jar:3.3.1.RELEASE]
at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onComplete(Operators.java:1858) ~[reactor-core-3.3.1.RELEASE.jar:3.3.1.RELEASE]
at reactor.core.publisher.Operators.complete(Operators.java:132) ~[reactor-core-3.3.1.RELEASE.jar:3.3.1.RELEASE]
at reactor.core.publisher.MonoEmpty.subscribe(MonoEmpty.java:45) ~[reactor-core-3.3.1.RELEASE.jar:3.3.1.RELEASE]
at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.3.1.RELEASE.jar:3.3.1.RELEASE]
For some reason during save in SimpleR2dbcRepository library class it doesn't consider the objectToSave as new, but then it fails to update as it is in reality doesn't exist.
// SimpleR2dbcRepository#save
#Override
#Transactional
public <S extends T> Mono<S> save(S objectToSave) {
Assert.notNull(objectToSave, "Object to save must not be null!");
if (this.entity.isNew(objectToSave)) { // not new
....
}
}
Why it is happening and what is the problem?

TL;DR: How should Spring Data know if your object is new or whether it should exist?
Relational Spring Data Repositories (both, JDBC and R2DBC) must differentiate on [Reactive]CrudRepository.save(…) whether the given object is new or whether it exists in your database. Performing a save(…) operation results either in an INSERT or UPDATE statement. Issuing the wrong statement either causes a primary key violation or a no-op as standard SQL does not have a way to express an upsert.
Spring Data JDBC|R2DBC use by default the presence/absence of the #Id value. Generated primary keys are a widely used mechanism. If the primary key is provided, the entity is considered existing. If the id value is null, the entity is considered new.
Read more in the reference documentation about Entity State Detection Strategies.

You have to implement Persistable because you’ve provided the #Id. The library needs to figure out, whether the row is new or whether it should exist. If your entity implements Persistable, then save(…) will use the outcome of isNew() to determine whether to issue an INSERT or UPDATE.
For example:
public class Product implements Persistable<Integer> {
#Id
private Integer id;
private String description;
private Double price;
#Transient
private boolean newProduct;
#Override
#Transient
public boolean isNew() {
return this.newProduct || id == null;
}
public Product setAsNew() {
this.newProduct = true;
return this;
}
}

May be you should consider this:
Choose data type of your id/Primary Key as INT/LONG and set it to AUTO_INCREMENT (something like below):
CREATE TABLE PRODUCT(id INT PRIMARY KEY AUTO_INCREMENT NOT NULL, modelname VARCHAR(30) , year VARCHAR(4), owner VARCHAR(50));
In your post request body, do not include id field.

Removing #ID issued insert statement

CSV file dynamic map to Database Tables using Hibernate

We have a requirement where around 25 CSV files would come each day & stored the Database in equivalent table structure.
Any of CSV file column structure could change in future by add new /remove columns & underlying DB table would align to the new format, without code change or redeployment.
Here are the choice of tech.
SpringBoot as Run time
Hibernate as JPA/DB Inetraction
Oracle DB as database
If using Hibernate, how to achieving this dynamic column management of the table as per the incoming CSV?
As far as I know, Hibernate would have Java Entity classes equivalent to the Table , which will be used to persists data. Any table change need Entity class change too.
Possible solution could be
just define basic JPA Entity & table structure (like ids & FKs linking to other tables etc) for CSV equivalent table,
then on arrival of CSV files, add the columns to the table by running the ALTER table command from application
In future 1st CSVs, if column added/removed , use similar alter commands
Is this achievable by Hibernate?
Or any other product better suited for this kind of tasks.

Task definition
We will have to implement a mechanism allowing for creating/deleting custom fields in real time avoiding the application restart, add a value into it and make sure the value is present in the application database. Besides we will have to make sure that the custom field can be used in queries.
Solution
Domain Model
We will first need a business entity class which we will experiment with. Let is be Contact class. There will be two persistent fields: id and name.
However besides these permanent and unchangeable fields the class should be some sort of construction to store values of custom fields. Map would be an ideal construction for this.
Let's create a base class for all business entities supporting custom fields - CustomizableEntity, that contains Map CustomProperties to work with custom fields:
package com.enterra.customfieldsdemo.domain;
import java.util.Map;
import java.util.HashMap;
public abstract class CustomizableEntity {
private Map customProperties;
public Map getCustomProperties() {
if (customProperties == null)
customProperties = new HashMap();
return customProperties;
}
public void setCustomProperties(Map customProperties) {
this.customProperties = customProperties;
}
public Object getValueOfCustomField(String name) {
return getCustomProperties().get(name);
}
public void setValueOfCustomField(String name, Object value) {
getCustomProperties().put(name, value);
}
}
Step 1 - base class CustomizableEntity
Inherit our class Contact from this base class:
package com.enterra.customfieldsdemo.domain;
import com.enterra.customfieldsdemo.domain.CustomizableEntity;
public class Contact extends CustomizableEntity {
private int id;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
Step 2 - Class Contact inherited from CustomizableEntity.
We should not forget about the mapping file for this class:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping auto-import="true" default-access="property" default-cascade="none" default-lazy="true">
<class abstract="false" name="com.enterra.customfieldsdemo.domain.Contact" table="tbl_contact">
<id column="fld_id" name="id">
<generator class="native"/>
</id>
<property name="name" column="fld_name" type="string"/>
<dynamic-component insert="true" name="customProperties" optimistic-lock="true" unique="false" update="true">
</dynamic-component>
</class>
</hibernate-mapping>
Step 3 - Mapping Class Contact.
Please note that properties id and name are done as all ordinary properties, however for customProperties we use a tag . Documentation on Hibernate 3.2.0GA says that the point of a dynamic-component is:
"The semantics of a mapping are identical to . The advantage of this kind of mapping is the ability to determine the actual properties of the bean at deployment time, just by editing the mapping document. Runtime manipulation of the mapping document is also possible, using a DOM parser. Even better, you can access (and change) Hibernate's configuration-time metamodel via the Configuration object."
Based on this regulation from Hibernate documentation we will be building this function mechanism.
HibernateUtil and hibernate.cfg.xml
After we are defined with the domain model of our application we have to create necessary conditions for Hibernate framework functioning. For this we have to create a configuration file hibernate.cfg.xml and class to work with the core Hibernate functions.
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration
PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="show_sql">true</property>
<property name="dialect">
org.hibernate.dialect.MySQLDialect</property>
<property name="cglib.use_reflection_optimizer">true</property>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/custom_fields_test</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password"></property>
<property name="hibernate.c3p0.max_size">50</property>
<property name="hibernate.c3p0.min_size">0</property>
<property name="hibernate.c3p0.timeout">120</property>
<property name="hibernate.c3p0.max_statements">100</property>
<property name="hibernate.c3p0.idle_test_period">0</property>
<property name="hibernate.c3p0.acquire_increment">2</property>
<property name="hibernate.jdbc.batch_size">20</property>
<property name="hibernate.hbm2ddl.auto">update</property>
</session-factory>
</hibernate-configuration>
Step 4 - Hibernate configuration file.
The file hibernate.cfg.xml does not contain anything noticeable except for this string:
<property name="hibernate.hbm2ddl.auto">update</property>
Step 5 - using auto-update.
Later we will explain in details on its purpose and tell more how we can go without it. There are several ways to implement class HibernateUtil. Our implementation will differ a bit from well known due to changes into Hibernate configuration.
package com.enterra.customfieldsdemo;
import org.hibernate.*;
import org.hibernate.mapping.PersistentClass;
import org.hibernate.tool.hbm2ddl.SchemaUpdate;
import org.hibernate.cfg.Configuration;
import com.enterra.customfieldsdemo.domain.Contact;
public class HibernateUtil {
private static HibernateUtil instance;
private Configuration configuration;
private SessionFactory sessionFactory;
private Session session;
public synchronized static HibernateUtil getInstance() {
if (instance == null) {
instance = new HibernateUtil();
}
return instance;
}
private synchronized SessionFactory getSessionFactory() {
if (sessionFactory == null) {
sessionFactory = getConfiguration().buildSessionFactory();
}
return sessionFactory;
}
public synchronized Session getCurrentSession() {
if (session == null) {
session = getSessionFactory().openSession();
session.setFlushMode(FlushMode.COMMIT);
System.out.println("session opened.");
}
return session;
}
private synchronized Configuration getConfiguration() {
if (configuration == null) {
System.out.print("configuring Hibernate ... ");
try {
configuration = new Configuration().configure();
configuration.addClass(Contact.class);
System.out.println("ok");
} catch (HibernateException e) {
System.out.println("failure");
e.printStackTrace();
}
}
return configuration;
}
public void reset() {
Session session = getCurrentSession();
if (session != null) {
session.flush();
if (session.isOpen()) {
System.out.print("closing session ... ");
session.close();
System.out.println("ok");
}
}
SessionFactory sf = getSessionFactory();
if (sf != null) {
System.out.print("closing session factory ... ");
sf.close();
System.out.println("ok");
}
this.configuration = null;
this.sessionFactory = null;
this.session = null;
}
public PersistentClass getClassMapping(Class entityClass){
return getConfiguration().getClassMapping(entityClass.getName());
}
}
Step 6 - HibernateUtils class.
Alongside with usual methods like getCurrentSession(), getConfiguration(), which is necessary for regular work of the application based on Hibernate, we also have implemented such methods as: reset() and getClassMapping(Class entityClass). In the method getConfiguration(), we configure Hibernate and add class Contact into the configuration.
Method reset() has been used to close all used by Hibernate resources and clearing all of its settings:
public void reset() {
Session session = getCurrentSession();
if (session != null) {
session.flush();
if (session.isOpen()) {
System.out.print("closing session ... ");
session.close();
System.out.println("ok");
}
}
SessionFactory sf = getSessionFactory();
if (sf != null) {
System.out.print("closing session factory ... "); sf.close();
System.out.println("ok");
}
this.configuration = null;
this.sessionFactory = null;
this.session = null;
}
Step 7 - method reset()
Method getClassMapping(Class entityClass) returns object PersistentClass, that contains full information on mapping the related entity. In particular the manipulations with the object PersistentClass allow modifying the set of attributes of the entity class in the run-time.
public PersistentClass getClassMapping(Class entityClass){
return
getConfiguration().getClassMapping(entityClass.getName());
}
Step 8 - method getClassMapping(Class entityClass).
Manipulations with mapping
Once we have the business entity class (Contact) available and the main class to interact with Hibernate we can start working. We can create and save samples of the Contact class. We can even place some data into our Map customProperties, however we should be aware that this data (stored in Map customProperties) are not saved to the DB.
To have the data saved we should provide for the mechanism of creating custom fields in our classs and make it the way Hibernate knows how to work with them.
To provide for class mapping manipulation we should create some interface. Let's call it CustomizableEntityManager. Its name should reflect the purpose of the interface managing a business entity, its contents and attributes:
package com.enterra.customfieldsdemo;
import org.hibernate.mapping.Component;
public interface CustomizableEntityManager {
public static String CUSTOM_COMPONENT_NAME = "customProperties";
void addCustomField(String name);
void removeCustomField(String name);
Component getCustomProperties();
Class getEntityClass();
}
Step 9 - Interface CustomizableEntityManager
The main methods for the interface are: void addCustomField(String name) and void removeCustomField(String name). These should created and remove our custom field in the mapping of the corresponding class.
Below is the way to implement the interface:
package com.enterra.customfieldsdemo;
import org.hibernate.cfg.Configuration;
import org.hibernate.mapping.*;
import java.util.Iterator;
public class CustomizableEntityManagerImpl implements CustomizableEntityManager {
private Component customProperties;
private Class entityClass;
public CustomizableEntityManagerImpl(Class entityClass) {
this.entityClass = entityClass;
}
public Class getEntityClass() {
return entityClass;
}
public Component getCustomProperties() {
if (customProperties == null) {
Property property = getPersistentClass().getProperty(CUSTOM_COMPONENT_NAME);
customProperties = (Component) property.getValue();
}
return customProperties;
}
public void addCustomField(String name) {
SimpleValue simpleValue = new SimpleValue();
simpleValue.addColumn(new Column("fld_" + name));
simpleValue.setTypeName(String.class.getName());
PersistentClass persistentClass = getPersistentClass();
simpleValue.setTable(persistentClass.getTable());
Property property = new Property();
property.setName(name);
property.setValue(simpleValue);
getCustomProperties().addProperty(property);
updateMapping();
}
public void removeCustomField(String name) {
Iterator propertyIterator = customProperties.getPropertyIterator();
while (propertyIterator.hasNext()) {
Property property = (Property) propertyIterator.next();
if (property.getName().equals(name)) {
propertyIterator.remove();
updateMapping();
return;
}
}
}
private synchronized void updateMapping() {
MappingManager.updateClassMapping(this);
HibernateUtil.getInstance().reset();
// updateDBSchema();
}
private PersistentClass getPersistentClass() {
return HibernateUtil.getInstance().getClassMapping(this.entityClass);
}
}
Step 10 - implementing interface CustomizableEntityManager
First of all we should point out that when creating class CustomizableEntityManager we specify the business entity class the manager will operate. This class is passed as a parameter to designer CustomizableEntityManager:
private Class entityClass;
public CustomizableEntityManagerImpl(Class entityClass) {
this.entityClass = entityClass;
}
public Class getEntityClass() {
return entityClass;
}
Step 11 - class designer CustomizableEntityManagerImpl
Now we should get more interested in how to implement method void addCustomField(String name):
public void addCustomField(String name) {
SimpleValue simpleValue = new SimpleValue();
simpleValue.addColumn(new Column("fld_" + name));
simpleValue.setTypeName(String.class.getName());
PersistentClass persistentClass = getPersistentClass();
simpleValue.setTable(persistentClass.getTable());
Property property = new Property();
property.setName(name);
property.setValue(simpleValue);
getCustomProperties().addProperty(property);
updateMapping();
}
Step 12 - creating custom field.
As we can see from the implementation, Hibernate offers more options in working with properties of persistent objects and their representation in the DB. As per the essence of the method:
1) We create class SimpleValue that allow us to denote how the value of this custom field will be stored in the DB in which field and table of the DB:
SimpleValue simpleValue = new SimpleValue();
simpleValue.addColumn(new Column("fld_" + name));
simpleValue.setTypeName(String.class.getName());
PersistentClass persistentClass = getPersistentClass();
simpleValue.setTable(persistentClass.getTable());
Step 13 - creating new column of the table.
2) We create a property of the persistent object and add a dynamic component into it (!), that we have planned to be used for this purpose:
Property property = new Property()
property.setName(name)
property.setValue(simpleValue)
getCustomProperties().addProperty(property)
Step 14 - creating object property.
3) And finally we should make our application perform certain changes in the xml files and update the Hibernate configuration. This can be done via method updateMapping();
It is necessary to clarify the purpose of another two get-methods which have been used in the code above. The first method is getCustomProperties():
public Component getCustomProperties() {
if (customProperties == null) {
Property property = getPersistentClass().getProperty(CUSTOM_COMPONENT_NAME);
customProperties = (Component) property.getValue();
}
return customProperties;
}
Step 15 - getting CustomProperties as Component.
This method finds and returns object Component corresponding to the tag in the mapping of our business entity.
The second method is updateMapping():
private synchronized void updateMapping() {
MappingManager.updateClassMapping(this);
HibernateUtil.getInstance().reset();
// updateDBSchema();
}
Step 16 - method updateMapping().
The method is in charge for storing the updated mapping of the persistent class and updates the configuration status of Hibernate to make further changes that we make valid when the changes take effect.
By the way we should get back to the string:
<property name="hibernate.hbm2ddl.auto">update</property>
of the Hibernate configuration. If this string was missing we would have to launch executing updates of the DB schema using hibernate utilities. However using the setting allows us to avoid this.
Saving mapping
Modifications to mapping made in run-time do not save by themselves into the corresponding xml mapping file and to make the changes to get activated at next launch of the application we need to manually save changes to the corresponding mapping file.
To do this we will be using class MappingManager the main purpose of which is to save mapping of the designated business entity to its xml mapping file:
package com.enterra.customfieldsdemo;
import com.enterra.customfieldsdemo.domain.CustomizableEntity;
import org.hibernate.Session;
import org.hibernate.mapping.Column;
import org.hibernate.mapping.Property;
import org.hibernate.type.Type;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import java.util.Iterator;
public class MappingManager {
public static void updateClassMapping(CustomizableEntityManager entityManager) {
try {
Session session = HibernateUtil.getInstance().getCurrentSession();
Class<? extends CustomizableEntity> entityClass = entityManager.getEntityClass();
String file = entityClass.getResource(entityClass.getSimpleName() + ".hbm.xml").getPath();
Document document = XMLUtil.loadDocument(file);
NodeList componentTags = document.getElementsByTagName("dynamic-component");
Node node = componentTags.item(0);
XMLUtil.removeChildren(node);
Iterator propertyIterator = entityManager.getCustomProperties().getPropertyIterator();
while (propertyIterator.hasNext()) {
Property property = (Property) propertyIterator.next();
Element element = createPropertyElement(document, property);
node.appendChild(element);
}
XMLUtil.saveDocument(document, file);
} catch (Exception e) {
e.printStackTrace();
}
}
private static Element createPropertyElement(Document document, Property property) {
Element element = document.createElement("property");
Type type = property.getType();
element.setAttribute("name", property.getName());
element.setAttribute("column", ((Column)
property.getColumnIterator().next()).getName());
element.setAttribute("type",
type.getReturnedClass().getName());
element.setAttribute("not-null", String.valueOf(false));
return element;
}
}
Step 17 - the utility to update mapping of the persistent class.
The class literally performs the following:
Defines a location and loads xml mapping for the designated business entity into the DOM Document object for further manipulations with it;
Finds the element of this document . In particular here we store the custom fields and its contents we change;
Delete (!) all embedded elements from this element;
For any persistent property contained in our component that is in charge for the custom fields storage, we create a specific document element and define attributes for the element from the corresponding property;
Save this newly created mapping file.
When manipulating XML we use (as we can see from the code) class XMLUtil, that in general can be implemented in any way though it should correctly load and save the xml file.
Our implementation is given at the Step below:
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Document;
import org.xml.sax.SAXException;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.Transformer;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.dom.DOMSource;
import java.io.IOException;
import java.io.FileOutputStream;
public class XMLUtil {
public static void removeChildren(Node node) {
NodeList childNodes = node.getChildNodes();
int length = childNodes.getLength();
for (int i = length - 1; i > -1; i--)
node.removeChild(childNodes.item(i));
}
public static Document loadDocument(String file)
throws ParserConfigurationException, SAXException, IOException {
DocumentBuilderFactory factory =DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
return builder.parse(file);
}
public static void saveDocument(Document dom, String file)
throws TransformerException, IOException {
TransformerFactory tf = TransformerFactory.newInstance();
Transformer transformer = tf.newTransformer();
transformer.setOutputProperty(OutputKeys.DOCTYPE_PUBLIC, dom.getDoctype().getPublicId());
transformer.setOutputProperty(OutputKeys.DOCTYPE_SYSTEM, dom.getDoctype().getSystemId());
DOMSource source = new DOMSource(dom);
StreamResult result = new StreamResult();
FileOutputStream outputStream = new FileOutputStream(file);
result.setOutputStream(outputStream);
transformer.transform(source, result);
outputStream.flush();
outputStream.close();
}
}
Source: Please refer this article for more detail

The onFlushDirty Hibernate Interceptor method is never called

Question: Why MyInterceptor#onFlushDirty is never called?
I extend AbstractEntityManagerFactoryBean in xml configs like
<bean id="myEntityManagerFactory" parent="abstractEntityManagerFactoryBean" abstract="true">
<property name="entityInterceptor">
<bean class="xxxx.MyInterceptor"/>
</property>
</bean>
<bean id="abstractEntityManagerFactoryBean" class="xxxx.MyEntityManagerFactoryBean"/>
MyEntityManagerFactoryBean
public class MyEntityManagerFactoryBean extends AbstractEntityManagerFactoryBean implements LoadTimeWeaverAware {
private Interceptor entityInterceptor;
public Interceptor getEntityInterceptor() {
return entityInterceptor;
}
public void setEntityInterceptor(Interceptor interceptor) {
entityInterceptor = interceptor;
}
}
MyInterceptor:
public class MyInterceptor extends EmptyInterceptor {
public MyInterceptor() {
System.out.println("init"); // Works well
}
// PROBLEM - is never called
#Override
public boolean onFlushDirty(Object entity,
Serializable id,
Object[] currentState,
Object[] previousState,
String[] propertyNames,
Type[] types) {
if (entity instanceof File) {
.....
}
return false;
}
}
UPDATE: [explanation why custom dirty policy looks like not my way]
I want update modified timestamp each time I change something in Folder entity EXCEPT folderPosition. In the same time folderPosition should be persistent and not transient (means cause entity to be dirty).
Due I use Spring Transactional and Hibernate Templates, there is some nuances:
1) I can't update modified timestamp at the end of each setter like:
public void setXXX(XXX xxx) {
//PROBLEM: Hibernate templates collect object via setters,
//means simple get query will cause multiple 'modified' timestamp updates
this.xxx = xxx;
this.modified = new Date();
}
2) I can't call setModified manually, because it has about 25 fields, and setXXX for each field is scattered across whole app. And I have no power to make refactoring.
#Entity
public class Folder {
/**
* GOAL: Changing of each of these fields except 'folderPosition' should cause
* 'modified' timestamp update
*/
private long id;
private String name;
private Date created;
private Date modified;
private Integer folderLocation;
#PreUpdate
public void preUpdate() {
//PROBLEM : change modified even if only location field has been changed!
//PROBLEM: need to know which fields have been updated!
modified = new Date();
}
....
}

You need to extend the findDirty method not onFlushDirty. Check this tutorial for a detail explanation with a reference to a GitHub working example.