Validating Entity and Get Error Messages - JPA , eclipselink

[showakath Naseem]

Here is my code, I would like to Validate DeploymentConfiguration Entity before saving to database. I have 3 more different entities – I have to write validation for other entities also. Note: Finally I will call these methods and exposing as a Rest Services (Jersy)
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1) DeploymentConfiguration is model/entity

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package com.Demo.persistence.model;

import java.io.Serializable;
import java.util.List;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.ElementCollection;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
import javax.validation.Valid;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Pattern;
import javax.validation.constraints.Size;

      public class DeploymentConfiguration implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @Column(name= DBConstants.DEPLOYMENT_ID,length = 255)
    @NotNull(message="DepoymentId type must be specified.")
    @Size(min=1, max=255)
    //@Valid
    private String depoymentId;

    @Basic
    @Column(name = DBConstants.SERVER_TYPE_VALUE, length = 255) 
    @NotNull(message="Deployment Server must be specified.")
    @Size(min=1, max=255)
    @Pattern(regexp="^(Dev|QA|Production)$",message="Invalid Servertype
private String deploymentServerValue;

     public String getDepoymentId () {
        return depoymentId;
    }

    public void setConnectionId(String depoymentId) {
        this.depoymentId = depoymentId;
    }

    public String getDeploymentServerValue () {
        return deploymentServerValue;
    }

    public void setDeploymentServerValue (String deploymentServerValue) 
{
        this.deploymentServerValue = deploymentServerValue;
}

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2) DaoImplementation
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import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import javax.persistence.EntityManager;
import javax.persistence.TypedQuery;
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.ValidatorFactory;
public class DeploymentConfigurationDaoImpl 
{
EntityManagerProvider entityManagerProvider;
public void saveConnectionConfigurations(ConnectionConfiguration connConfig) {
        LOG.debug("Saving depoyment Configuration");
        if (null == connConfig) {
            return;
        }
        EntityManager em = null;
        em = getEntityManagerProvider().getEntityManager();
        try {
            em.getTransaction().begin();

                em.persist(connConfig);
                em.getTransaction().commit();
                em.getEntityManagerFactory().getCache().evictAll();
                LOG.debug("Persisting data");

        } 
catch (Exception ex) 
{
LOG.error("Error while persisting the depoyment Configuration", ex);

} finally {
    if (em != null && em.isOpen())
    em.close();

}

}

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3-.Persistence .xml
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<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
<persistence-unit name="com.Demo.persistence"
transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<class>com.Demo.persistence.model.DeploymentConfiguration</class>
<shared-cache-mode>ALL</shared-cache-mode>
<properties>
<property name="eclipselink.ddl-generation" value="create-or-extend-tables" />
</properties>
</persistence-unit>
</persistence>

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I am using below dependencies


<!-- JPA dependencies - Start -->
<dependency>
<groupId>org.eclipse.persistence</groupId>
<artifactId>eclipselink</artifactId>
</dependency>
<!-- JPA dependencies - Start -->

<!-- Spring dependencies - Start -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
</dependency>
<!-- Spring dependencies - End -->
<!-- slf4j dependencies - Start -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>com.springsource.slf4j.log4j</artifactId>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>com.springsource.slf4j.api</artifactId>
</dependency>
<!-- slf4j dependencies - End -->
<!-- Junits dependencies - Start -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>org.springframework.test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-expression</artifactId>
</dependency>
<dependency>
<groupId>org.testng</groupId>
<artifactId>testng</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>org.springframework.orm</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.servicemix.bundles</groupId>
<artifactId>org.apache.servicemix.bundles.derby</artifactId>
<scope>test</scope>
</dependency>
<!-- Junits dependencies - End -->

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I am newbie in JAVA, Springs, JPA ecipselink. –
could some one explain me how to write validations using Annotations. Note : we should use eclipselink ,springframework in our demo project, We are not using Spring MVC, we need to exposed our methods as Services (Jersy)