如何在Java SE中激活自动JPA实体验证？

Question

I activated entity validation in persistence.xml with

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
    <persistence-unit name="de.richtercloud_hibernate-automatic-validation_jar_1.0-SNAPSHOTPU" transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <validation-mode>AUTO</validation-mode>
        <properties>
            <property name="javax.persistence.jdbc.url" value="jdbc:derby:memory:myDB;create=true"/>
            <property name="javax.persistence.jdbc.user" value="app"/>
            <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.EmbeddedDriver"/>
            <property name="javax.persistence.jdbc.password" value="app"/>
            <property name="javax.persistence.schema-generation.database.action" value="create"/>
        </properties>
    </persistence-unit>
</persistence>

and declared the Maven dependencies

<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-core</artifactId>
    <version>5.3.3.Final</version>
</dependency>
<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-validator</artifactId>
    <version>6.0.11.Final</version>
</dependency>
<dependency>
    <groupId>org.apache.derby</groupId>
    <artifactId>derby</artifactId>
    <version>10.14.2.0</version>
</dependency>

Assuming I have a very simple

@Entity
public class Entity0 implements Serializable {
    @Id
    private Long id;
    @Basic
    @NotNull
    private String property0;

    public Entity0() {
    }

    public Entity0(Long id,
            String property0) {
        this.id = id;
        this.property0 = property0;
    }

    [getter and setter for id and property0]
}

and persist it with

EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("de.richtercloud_hibernate-automatic-validation_jar_1.0-SNAPSHOTPU");
EntityManager entityManager = entityManagerFactory.createEntityManager();
Entity0 entity0 = new Entity0(1l, "abc");
entityManager.getTransaction().begin();
entityManager.persist(entity0);
entityManager.flush();
entityManager.getTransaction().commit();
entityManager.close();
entityManager = entityManagerFactory.createEntityManager();
entityManager.getTransaction().begin();
entity0 = entityManager.merge(entity0);
entity0.setProperty0(null);
entityManager.merge(entity0);
entityManager.flush();
entityManager.getTransaction().commit();
entityManager.close();
entityManagerFactory.close();

Why does entityManager.merge(entity0); entityManager.flush(); entityManager.merge(entity0); entityManager.flush(); not cause a validation constraint violation of the automatically invoked validator after entity0.setProperty0(null); ? Afaik, the presence of a validation implementation on the classpath enables the JPA entity validation.

Hibernate as JPA and Hibernate Validator are example implementations. I assume there's a solution for all JPA providers and JSR 303 implementations.

I'm aware that I can validate the entities manually which is out of the scope of the question.

An SSCCE is provided at https://gitlab.com/krichter/hibernate-automatic-validation . It does not contain more information than the MCVE above and merely allows to reproduce the issue locally as easily as possible.

Answer 1

I needed to add

<dependency>
    <groupId>javax.el</groupId>
    <artifactId>javax.el-api</artifactId>
    <version>3.0.0</version>
</dependency>
<dependency>
    <groupId>org.glassfish.web</groupId>
    <artifactId>javax.el</artifactId>
    <version>2.2.6</version>
</dependency>

to the list of dependencies.