eclipselink

问题 If connection pooling is not defined in the persistence.xml for eclipse link, what is the default behavior? Will it open and close a JDBC connection for every transaction? Will it create a connection pool with some defaults? 回答1: The default connection pooling for EclipseLink when not using a data source is a pool of min/max 32 connections, with an initial of 1 connections. So each transaction will use a pooled connection, and not connect/disconnect. 回答2: If you use an application server

问题 I ran into some similar questions on StackOverflow, tried the solutions, but did not find an answer. I am using a fairly common JPA strategy to set last modified times on some entities. Set up the columns and the fields, then tag a method with @PreUpdate and let it set them equal to the current time. The problem is that I can see in the debugger that the method is being called and that the field is being updated, however in my DB logs I only see a SQL call to UPDATE the changed field that

问题 I have an issue I can't get my head around. In hibernate I have no problem with the following: @GeneratedValue( strategy = GenerationType.AUTO, generator = "email-seq-gen" ) @SequenceGenerator( name="email-seq-gen", sequenceName="EMAIL_SEQ_GEN", allocationSize=500 ) Then in my schema.ddl I have this: CREATE SEQUENCE EMAIL_SEQ_GEN START 1 INCREMENT 500; Not much to see here. Everything works as expected. However, if I switch my provider to EclipseLink I get this error: The sequence named

问题 I'm struggling with a problem with an EJB3 class that manages a non-trivial data model. I have constraint validation exceptions being thrown when my container-managed transactional methods commit. I want to prevent them from being wrapped in EJBException , instead throwing a sane application exception that callers can handle. To wrap it in a suitable application exception, I must be able to catch it. Most of the time a simple try/catch does the job because the validation exception is thrown

问题 What should I prefer when updating the database? What are the pros & cons with either method and when shall I use the one or the other? public void disemployEmployee(Integer employeeId, Date endDate) { Employee employee = (Employee)em.find("Employee", employeeId); employee.getPeriod().setEndDate(endDate); em.flush(); } public void disemployEmployee(Integer employeeId, Date endDate) { Employee employee = (Employee)em.find("Employee", employeeId); em.getTransaction().begin(); employee.getPeriod

问题 I am running a test on eclipselink JPA 2, to determine how lazy loading of a collection is working. I have assumed, the if you load an entity, then all eager elements are loaded first of all, then, within the JPA session, the lazy elements are loaded when you ask for them, or touch them (refer to them in some way, like getting the size of a lazy collection). The problem I have is this: when I detach the entity from the session, the lazy collection is loaded, and is available, even though I

问题 I am using EclipseLink 2.4.1 with Glassfish and a MySQL database for persisting entities. I added a field to an entity, and when I try to persist this entity it says the new field is 'unknown'. How are we supposed to use the new 'create-or-extend-tables' feature? I would have thought it would create a new column for this field. Some relevant information is below, let me know if you want more. Thanks in advance! Stack Trace ... Caused by: Exception [EclipseLink-4002] (Eclipse Persistence

问题 I'm running a sample (which i can't find anymore) from Blaise Doughans blog on Glassfish 3 using EclipseLink 2.5 MOXy for JAXB service. @XmlRootElement @XmlAccessorType(XmlAccessType.FIELD) public class Company { @XmlElementWrapper(name="employees") @XmlElement(name = "employee", type=Employee.class) private List<Employee> employees; } @XmlAccessorType(XmlAccessType.FIELD) public class Employee { private String id; private String name; } I added some annotations to the classes, to produce the

问题 Important Notice : If you are reading this post, then consider looking into this post too for in-depth discussions. It is a quite usual practice/situation/requirement where children of a parent may be migrated to another parent. What happens, if orphanRemoval is set to true on the inverse side of such relationships? Consider as an example, any simple one-to-many relationship as follows. Inverse side (Department) : @OneToMany(mappedBy = "department", fetch = FetchType.LAZY, cascade =

问题 I have the following XML structure, which is modelling a single concept across multiple XML elements. This format is not in my control. <Output> <Wrapper> <Channel> <id>1</id> <type>x</type> </Channel> <Channel> <id>2</id> <type>y</type> </Channel> <ChannelName> <id>1</id> <name>Channel name</name> </ChannelName> <ChannelName> <id>2</id> <name>Another channel name</name> </ChannelName> </Wrapper> </Output> I want to model this in a database that I do have control over and can have a more