title: Hibernate exception handling
body: <p>I've got a little 'complex' question.<br></p>
  
  <p>I'm using Hibernate/JPA to make transactions with a DB.<br></p>
  
  <p>I'm not the DBA, and a client consumes my application, a RESTful web service. My problem is that the DB is altered (not very often, but it still changes). Also, the client does not always respect input for my application (length, type, etc.). When this happens Hibernate throws an exception. The exception is difficult to translate and read from the log, because it has nested exceptions and consists of a lot of text: like I said, very difficult to understand.<br></p>
  
  <p>I want to know if it's possible to handle exceptions on entity level, throwing maybe a customized exception.</p>
  
  <p>I thank your patience and help in advance.</p>
  
  <p><strong>EDIT:</strong></p>
  
  <p>Fianlly I managed to do what I wanted, not sure if it's done the <em>right way</em>.</p>
  
  <p><em>App.java</em></p>
  
  <pre><code>package com.mc;  
  
  import org.hibernate.Session;  
  import com.mc.stock.Stock;  
  import com.mc.util.HibernateUtil;  
  import javax.persistence.EntityManager;  
  
  public class App {  
  
      public static void main(String[] args) {  
          Set&lt;ConstraintViolation&lt;Stock&gt;&gt; violations;
          validator = Validation.buildDefaultValidatorFactory().getValidator();
          Scanner scan = new Scanner(System.in);
  
          EntityManager em = null;
  
          System.out.println("Hibernate one to many (Annotation)");
          Session session = HibernateUtil.getSessionFactory().openSession();
  
          session.beginTransaction();
  
  
          Stock stock = new Stock();
          String nextLine = scan.nextLine();
          stock.setStockCode(nextLine.toString());
          nextLine = scan.nextLine();
          stock.setStockName(nextLine.toString());
  
  
          violations = validator.validate(stock);
          if (violations.size() &gt; 0) {
              StringBuilder excepcion = new StringBuilder();
              for (ConstraintViolation&lt;Stock&gt; violation : violations) {
                  excepcion.append(violation.getMessageTemplate());
                  excepcion.append("\n");
              }
              System.out.println(excepcion.toString());
          }
          session.save(stock);
          session.getTransaction().commit();
      }  
  }  
  </code></pre>
  
  <p><em>FieldMatch.java</em></p>
  
  <pre><code>package com.mc.constraints;  
  
  import com.mc.constraints.impl.FieldMatchValidator;  
  
  import javax.validation.Constraint;  
  import javax.validation.Payload;  
  import java.lang.annotation.Documented;  
  import static java.lang.annotation.ElementType.ANNOTATION_TYPE;  
  import static java.lang.annotation.ElementType.TYPE;  
  import java.lang.annotation.Retention;  
  import static java.lang.annotation.RetentionPolicy.RUNTIME;  
  import java.lang.annotation.Target;  
  
  @Target({TYPE, ANNOTATION_TYPE})  
  @Retention(RUNTIME)  
  @Constraint(validatedBy = FieldMatchValidator.class)  
  @Documented  
  public @interface FieldMatch {  
  
      String message() default "{constraints.fieldmatch}";  
  
      Class&lt;?&gt;[] groups() default {};  
  
      Class&lt;? extends Payload&gt;[] payload() default {};  
  
      String first();  
  
      String second();  
  
      @Target({TYPE, ANNOTATION_TYPE})  
      @Retention(RUNTIME)  
      @Documented  
      @interface List {  
  
          FieldMatch[] value();  
      }  
  }  
  </code></pre>
  
  <p><em>FieldMatchValidator.java</em></p>
  
  <pre><code>package com.mc.constraints.impl;  
  
  import javax.validation.ConstraintValidator;  
  import javax.validation.ConstraintValidatorContext;  
  import com.mc.constraints.FieldMatch;  
  import org.apache.commons.beanutils.BeanUtils;  
  
  public class FieldMatchValidator implements ConstraintValidator&lt;FieldMatch, Object&gt; {  
  
      private String firstFieldName;  
      private String secondFieldName;  
  
      @Override  
      public void initialize(final FieldMatch constraintAnnotation) {  
          firstFieldName = constraintAnnotation.first();  
          secondFieldName = constraintAnnotation.second();  
      }  
  
      @Override  
      public boolean isValid(final Object value, final ConstraintValidatorContext context) {  
          try {  
              final Object firstObj = BeanUtils.getProperty(value, firstFieldName);  
              final Object secondObj = BeanUtils.getProperty(value, secondFieldName);  
  
              return firstObj == null &amp;&amp; secondObj == null || firstObj != null &amp;&amp; firstObj.equals(secondObj);  
          } catch (final Exception ignore) {  
              // ignore  
          }  
          return true;  
      }  
  }  
  </code></pre>
  
  <p><em>Stock.java</em></p>
  
  <pre><code>package com.mc.stock;  
  
  import com.mc.constraints.FieldMatch;  
  import java.io.Serializable;  
  import java.util.HashSet;  
  import java.util.Set;  
  import javax.persistence.Basic;  
  import javax.persistence.Column;  
  import javax.persistence.Entity;  
  import javax.persistence.GeneratedValue;  
  import javax.persistence.GenerationType;  
  import javax.persistence.Id;  
  import javax.persistence.NamedQueries;  
  import javax.persistence.NamedQuery;  
  import javax.persistence.OneToMany;  
  import javax.persistence.SequenceGenerator;  
  import javax.persistence.Table;  
  import javax.xml.bind.annotation.XmlRootElement;  
  import javax.xml.bind.annotation.XmlTransient;  
  import org.hibernate.annotations.Cascade;  
  import org.hibernate.annotations.CascadeType;  
  import org.hibernate.validator.constraints.Length;  
  
  @Entity  
  @Table(name = "STOCK")  
  @XmlRootElement  
  @NamedQueries({  
      @NamedQuery(name = "Stock.findAll", query = "SELECT s FROM Stock s"),  
      @NamedQuery(name = "Stock.findByStockId", query = "SELECT s FROM Stock s WHERE s.stockId = :stockId"),  
      @NamedQuery(name = "Stock.findByStockCode", query = "SELECT s FROM Stock s WHERE s.stockCode = :stockCode"),  
      @NamedQuery(name = "Stock.findByStockName", query = "SELECT s FROM Stock s WHERE s.stockName = :stockName")})  
  @FieldMatch.List({  
      @FieldMatch(first = "stockCode", second = "stockName", message = "Code and Stock must have same value")  
  })  
  public class Stock implements Serializable {  
  
      private static final long serialVersionUID = 1L;  
      @Id  
      @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "seq_stock_id")  
      @SequenceGenerator(name = "seq_stock_id", sequenceName = "seq_stock_id", initialValue = 1, allocationSize = 1)  
      @Basic(optional = false)  
      @Column(name = "STOCK_ID", unique = true, nullable = false)  
      private Integer stockId;  
      @Column(name = "STOCK_CODE")  
      private String stockCode;  
      @Length(min = 1, max = 20, message = "{wrong stock name length}")  
      @Column(name = "STOCK_NAME")  
      private String stockName;  
  
      public Stock() {  
      }  
  
      public Stock(Integer stockId) {  
          this.stockId = stockId;  
      }  
  
      public Integer getStockId() {  
          return stockId;  
      }  
  
      public void setStockId(Integer stockId) {  
          this.stockId = stockId;  
      }  
  
      public String getStockCode() {  
          return stockCode;  
      }  
  
      public void setStockCode(String stockCode) {  
          this.stockCode = stockCode;  
      }  
  
      public String getStockName() {  
          return stockName;  
      }  
  
      public void setStockName(String stockName) {  
          this.stockName = stockName;  
      }  
  
      @Override  
      public int hashCode() {  
          int hash = 0;  
          hash += (stockId != null ? stockId.hashCode() : 0);  
          return hash;  
      }  
  
      @Override  
      public boolean equals(Object object) {  
          // TODO: Warning - this method won't work in the case the id fields are not set  
          if (!(object instanceof Stock)) {  
              return false;  
          }  
          Stock other = (Stock) object;  
          if ((this.stockId == null &amp;&amp; other.stockId != null) || (this.stockId != null &amp;&amp; !this.stockId.equals(other.stockId))) {  
              return false;  
          }  
          return true;  
      }  
  
      @Override  
      public String toString() {  
          return "com.mc.stock.Stock[ stockId=" + stockId + " ]";  
      }  
  }  
  </code></pre>
  
  <p><em>HibernateUtil.java</em></p>
  
  <pre><code>package com.mc.util;  
  
  import org.hibernate.SessionFactory;  
  import org.hibernate.cfg.Configuration;  
  
  public class HibernateUtil {  
  
      private static final SessionFactory sessionFactory = buildSessionFactory();  
  
      private static SessionFactory buildSessionFactory() {  
          try {  
              // Create the SessionFactory from hibernate.cfg.xml  
              return new Configuration().configure().buildSessionFactory();  
          } catch (Throwable ex) {  
              // Make sure you log the exception, as it might be swallowed  
              System.err.println("Initial SessionFactory creation failed." + ex);  
              throw new ExceptionInInitializerError(ex);  
          }  
      }  
  
      public static SessionFactory getSessionFactory() {  
          return sessionFactory;  
      }  
  
      public static void shutdown() {  
          // Close caches and connection pools  
          getSessionFactory().close();  
      }  
  }  
  </code></pre>
  
  <p><em>Oracle DB Structure</em></p>
  
  <pre><code>CREATE TABLE stock  
  (  
      STOCK_ID  NUMBER(5)  NOT NULL ,  
      STOCK_CODE  VARCHAR2(10)  NULL ,  
      STOCK_NAME  VARCHAR2(20)  NULL   
  );  
  
  ALTER TABLE stock  
      add CONSTRAINT PK_STOCK_ID  PRIMARY KEY (STOCK_ID);  
  
  create sequence seq_stock_id   
     start with 1   
     increment by 1   
     nomaxvalue;  
  </code></pre>