Java Bean Validation Basics

Abstract

This post summarizes some quick and easy examples for the most common things you would want to do with the Java Beans Validation API (JSR 349, JSR 303). Remember, Beans Validation is independent of Java EE. Although it is built in as part of a Java EE compliant server, the API can also be used just as easily in a Java SE application. All these examples use Java SE.

Table of Contents

1. Basics
2. Custom Message Template
3. Custom Message Template with Variable Replacement
4. Custom Property Validator
5. Custom Class Validator
6. GroupSequence (Short Circuit)

Requirements

I did all of the work for this post using the following major technologies. You may be able to do the same thing with different technologies or versions, but no guarantees.

• Java 1.8.0_65_x64
• NetBeans 8.2
• Maven 3.0.5 (Bundled with NetBeans)

<dependency>
    <groupId>javax.validation</groupId>
    <artifactId>validation-api</artifactId>
    <version>1.1.0.Final</version>
</dependency>
<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-validator</artifactId>
    <version>5.1.2.Final</version>
</dependency>
<dependency>
    <groupId>javax.el</groupId>
    <artifactId>javax.el-api</artifactId>
    <version>2.2.4</version>
</dependency>
<dependency>
    <groupId>org.glassfish.web</groupId>
    <artifactId>javax.el</artifactId>
    <version>2.2.4</version>
</dependency>
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
    <scope>test</scope>
</dependency>

Download

Visit my GitHub page https://github.com/mjremijan to see all of my open source projects. The code for this post is located at: https://github.com/mjremijan/thoth-beanvalidation

Basics

This example shows the basics of bean validation using the built-in, standard constraints and the built-in, standard validators.

Listing 1.1 - Bean to validate

package org.thoth.beanvalidation.basics;

import javax.validation.constraints.NotNull;

public class Widget {

    @NotNull
    protected String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

Listing 1.2 - How to validate

package org.thoth.beanvalidation.basics;

import java.util.Set;
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;

public class WidgetTest {

    protected Validator validator;

    @Before
    public void before() {
        validator = Validation.buildDefaultValidatorFactory().getValidator();
    }

    @Test
    public void violations_size() {
        // setup
        Widget w = new Widget();

        // action
        Set<ConstraintViolation<Widget>> violations
            = validator.validate(w);

        // assert
        Assert.assertEquals(1, violations.size());
    }

    @Test
    public void violation_message() {
        // setup
        Widget w = new Widget();

        // action
        Set<ConstraintViolation<Widget>> violations
            = validator.validate(w);

        // assert
        ConstraintViolation<Widget> v
            = violations.stream().findFirst().get();
        Assert.assertEquals("may not be null", v.getMessage());
    }

    @Test
    public void violation_messageTemplate() {
        // setup
        Widget w = new Widget();

        // action
        Set<ConstraintViolation<Widget>> violations
            = validator.validate(w);

        // assert
        ConstraintViolation<Widget> v
            = violations.stream().findFirst().get();
        Assert.assertEquals("{javax.validation.constraints.NotNull.message}", v.getMessageTemplate());
    }

    @Test
    public void violation_propertyPath() {
        // setup
        Widget w = new Widget();

        // action
        Set<ConstraintViolation<Widget>> violations
            = validator.validate(w);

        // assert
        ConstraintViolation<Widget> v
            = violations.stream().findFirst().get();
        Assert.assertEquals("name", v.getPropertyPath().toString());
    }
}

Custom Message Template

This example shows how the built-in, standard constraints can be customized with a custom error message instead of using the built-in, standard error messages.

Listing 2.1 - ValidationMessages.properties

Candy.name.NotNull=A candy name is required.

Listing 2.2 - Bean to validate

package org.thoth.beanvalidation.custommessage;

import javax.validation.constraints.NotNull;

public class Candy {

    @NotNull(message = "{Candy.name.NotNull}")
    protected String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

Listing 2.3 - How to validate

package org.thoth.beanvalidation.custommessage;

import java.util.Set;
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import org.junit.Assert;
import org.junit.BeforeClass;
import org.junit.Test;

public class CandyTest {

    protected static Validator validator;

    @BeforeClass
    public static void before() {
        validator = Validation.buildDefaultValidatorFactory().getValidator();
    }

    @Test
    public void notnull_violation_message() {
        // setup
        Candy candy = new Candy();

        // action
        Set<ConstraintViolation<Candy>> violations
            = validator.validate(candy);

        // assert
        ConstraintViolation<Candy> v
            = violations.stream().findFirst().get();
        Assert.assertEquals("A candy name is required.", v.getMessage());
    }

    @Test
    public void notnull_violation_messageTemplate() {
        // setup
        Candy candy = new Candy();

        // action
        Set<ConstraintViolation<Candy>> violations
            = validator.validate(candy);

        // assert
        ConstraintViolation<Candy> v
            = violations.stream().findFirst().get();
        Assert.assertEquals("{Candy.name.NotNull}", v.getMessageTemplate());
    }
}

Custom Message Template with Variable Replacement

This example shows how the built-in, standard constraints can be configured with a custom error message which has variable values in the message which are replaced by bean validation at runtime. Examples of variables which can be replaced are the actual value which was validate and the min and max properties of a @Size constraint.

Listing 3.1 - ValidationMessages.properties

Candy.name.Size.message=The candy name "${validatedValue}" is invalid. It must be between {min} and {max} characters long

Listing 3.2 - Bean to validate

package org.thoth.beanvalidation.variablereplacement;

import javax.validation.constraints.Size;

public class Candy {
    private String name;

    @Size(message = "{Candy.name.Size.message}", min=5, max=10)
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

Listing 3.3 - How to validate

package org.thoth.beanvalidation.variablereplacement;

import java.util.Set;
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import org.junit.Assert;
import org.junit.BeforeClass;
import org.junit.Test;
import org.thoth.beanvalidation.variablereplacement.Candy;

public class CandyTest {

    protected static Validator validator;

    @BeforeClass
    public static void before() {
        validator = Validation.buildDefaultValidatorFactory().getValidator();
    }


    @Test
    public void does_the_constraint_have_the_correct_messageTemplate() {
        // setup
        Candy candy = new Candy();
        candy.setName("");

        // action
        Set<ConstraintViolation<Candy>> violations
            = validator.validate(candy);

        // assert
        ConstraintViolation<Candy> v
            = violations.stream().findFirst().get();
        Assert.assertEquals("{Candy.name.Size.message}", v.getMessageTemplate());
    }

    @Test
    public void is_the_message_correct_if_size_is_too_small() {
        // setup
        Candy candy = new Candy();
        candy.setName("foo");

        // action
        Set<ConstraintViolation<Candy>> violations
            = validator.validate(candy);

        // assert
        ConstraintViolation<Candy> v
            = violations.stream().findFirst().get();
        Assert.assertEquals("The candy name \"foo\" is invalid. It must be between 5 and 10 characters long", v.getMessage());
    }

    @Test
    public void is_the_message_correct_if_size_is_too_big() {
        // setup
        Candy candy = new Candy();
        candy.setName("123456789|1");

        // action
        Set<ConstraintViolation<Candy>> violations
            = validator.validate(candy);

        // assert
        ConstraintViolation<Candy> v
            = violations.stream().findFirst().get();
        Assert.assertEquals("The candy name \"123456789|1\" is invalid. It must be between 5 and 10 characters long", v.getMessage());
    }
}

Custom Property Validator

This example shows how to create your own constraint and your own validator for a property of a class.

Listing 4.1 - ValidationMessages.properties

org.thoth.beanvalidation.propertyvalidator.Excludes.message=The value "${validatedValue}" is one of {value} which is forbidden.

Listing 4.2 - Constraint annotation

package org.thoth.beanvalidation.propertyvalidator;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import javax.validation.Constraint;

@Target({
    ElementType.TYPE, ElementType.ANNOTATION_TYPE, ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = {ExcludesValidator.class})
@Documented
public @interface Excludes {

    String message() default "{org.thoth.beanvalidation.propertyvalidator.Excludes.message}";

    Class[] groups() default {};

    Class[] payload() default {};

    String[] value() default {};
}

Listing 4.3 - Constraint validator

package org.thoth.beanvalidation.propertyvalidator;

import java.util.Arrays;
import java.util.List;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;

public class ExcludesValidator
    implements ConstraintValidator< Excludes, String> {

    private List<String> excludeTheseValues;

    @Override
    public void initialize(Excludes arg) {
        String[] strarr = arg.value();
        if (strarr == null) {
            strarr = new String[]{};
        }
        excludeTheseValues = Arrays.asList(strarr);
    }

    @Override
    public boolean isValid(String value, ConstraintValidatorContext cvc) {
        if (excludeTheseValues.contains(value)) {
            return false;
        } else {
            return true;
        }
    }
}

Listing 4.4 - Bean to validate

package org.thoth.beanvalidation.propertyvalidator;

public class Candy {
    private String name;

    public Candy(String name) {
        this.name = name;
    }

    @Excludes({"foo", "bar", "shrubbery"})
    public String getName() {
        return name;
    }
}

Listing 4.5 - How to validate

package org.thoth.beanvalidation.propertyvalidator;

import java.util.Set;
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import static org.junit.Assert.assertEquals;
import org.junit.BeforeClass;
import org.junit.Test;

public class CandyTest {

    protected static Validator validator;

    @BeforeClass
    public static void before() {
        validator = Validation.buildDefaultValidatorFactory().getValidator();
    }


    @Test
    public void a_non_excludeded_name_should_not_give_you_a_constraint_violation() {
        // setup
        Candy candy = new Candy("hershey");

        // action
        Set<ConstraintViolation<Candy>> violations
            = validator.validate(candy);

        // assert
        assertEquals(0, violations.size());
    }


    @Test
    public void do_you_get_a_constraint_violation_if_you_use_excluded_name_foo() {
        // setup
        Candy candy = new Candy("foo");

        // action
        ConstraintViolation<Candy> violation
            = validator.validate(candy).iterator().next();

        // assert
        assertEquals("{org.thoth.beanvalidation.propertyvalidator.Excludes.message}", violation.getMessageTemplate());
        assertEquals("The value \"foo\" is one of [foo, bar, shrubbery] which is forbidden.", violation.getMessage());
    }


    @Test
    public void do_you_get_a_constraint_violation_if_you_use_excluded_name_bar() {
        // setup
        Candy candy = new Candy("bar");

        // action
        ConstraintViolation<Candy> violation
            = validator.validate(candy).iterator().next();

        // assert
        assertEquals("{org.thoth.beanvalidation.propertyvalidator.Excludes.message}", violation.getMessageTemplate());
        assertEquals("The value \"bar\" is one of [foo, bar, shrubbery] which is forbidden.", violation.getMessage());
    }


    @Test
    public void do_you_get_a_constraint_violation_if_you_use_excluded_name_shrubbery() {
        // setup
        Candy candy = new Candy("shrubbery");

        // action
        ConstraintViolation<Candy> violation
            = validator.validate(candy).iterator().next();

        // assert
        assertEquals("{org.thoth.beanvalidation.propertyvalidator.Excludes.message}", violation.getMessageTemplate());
        assertEquals("The value \"shrubbery\" is one of [foo, bar, shrubbery] which is forbidden.", violation.getMessage());
    }
}

Custom Class Validator

This example shows how to create your own constraint and your own validator which applies to an entire class.

Listing 5.1 - ValidationMessages.properties

org.thoth.beanvalidation.classvalidator.IdentificationExists.message=At least one of social security number, drivers license number, or passport number must exist.

Listing 5.2 - Constraint annotation

package org.thoth.beanvalidation.classvalidator;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import javax.validation.Constraint;
import javax.validation.Payload;

@Target({ElementType.TYPE, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = {IdentificationExistsValidator.class})
@Documented
public @interface IdentificationExists {

    String message() default "{org.thoth.beanvalidation.classvalidator.IdentificationExists.message}";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};
}

Listing 5.3 - Constraint validator

package org.thoth.beanvalidation.classvalidator;

import java.util.Objects;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;

public class IdentificationExistsValidator implements ConstraintValidator<IdentificationExists, Identification> {

    @Override
    public void initialize(IdentificationExists a) {}

    @Override
    public boolean isValid(Identification t, ConstraintValidatorContext cvc) {
        boolean invalid =
            Objects.equals(t.getDriversLicenseNumber(), null)
            &&
            Objects.equals(t.getPassportNumber(), null)
            &&
            Objects.equals(t.getSocialSecurityNumber(), null)
        ;
        return !invalid;
    }
}

Listing 5.4 - Bean to validate

package org.thoth.beanvalidation.classvalidator;

@IdentificationExists
public class Identification {
    protected String socialSecurityNumber;
    protected String driversLicenseNumber;
    protected String passportNumber;

    public String getSocialSecurityNumber() {
        return socialSecurityNumber;
    }

    public void setSocialSecurityNumber(String socialSecurityNumber) {
        this.socialSecurityNumber = socialSecurityNumber;
    }

    public String getDriversLicenseNumber() {
        return driversLicenseNumber;
    }

    public void setDriversLicenseNumber(String driversLicenseNumber) {
        this.driversLicenseNumber = driversLicenseNumber;
    }

    public String getPassportNumber() {
        return passportNumber;
    }

    public void setPassportNumber(String passportNumber) {
        this.passportNumber = passportNumber;
    }
}

Listing 5.5 - How to validate

package org.thoth.beanvalidation.classvalidator;

import java.util.Set;
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;

public class IdentificationTest {

protected Validator validator;

    @Before
    public void before() {
        validator = Validation.buildDefaultValidatorFactory().getValidator();
    }

    @Test
    public void violation_if_all_are_missing() {
        // setup
        Identification id = new Identification();

        // action
        Set<ConstraintViolation<Identification>> violations
            = validator.validate(id);

        // assert
        ConstraintViolation<Identification> v
            = violations.stream().findFirst().get();
        Assert.assertEquals("At least one of social security number, drivers license number, or passport number must exist.", v.getMessage());
    }

    @Test
    public void no_violation_if_social_security_number_exists() {
        // setup
        Identification id = new Identification();
        id.setSocialSecurityNumber("a");

        // action
        Set<ConstraintViolation<Identification>> violations
            = validator.validate(id);

        // assert
        Assert.assertEquals(0, violations.size());
    }

    @Test
    public void no_violation_if_drivers_license_number_exists() {
        // setup
        Identification id = new Identification();
        id.setDriversLicenseNumber("a");

        // action
        Set<ConstraintViolation<Identification>> violations
            = validator.validate(id);

        // assert
        Assert.assertEquals(0, violations.size());
    }

    @Test
    public void no_violation_if_passport_number_exists() {
        // setup
        Identification id = new Identification();
        id.setPassportNumber("a");

        // action
        Set<ConstraintViolation<Identification>> violations
            = validator.validate(id);

        // assert
        Assert.assertEquals(0, violations.size());
    }
}

GroupSequence (Short Circuit)

This example shows how to use @GroupSequence as a short circuit when doing validation. This means if the 1st round of validations do not pass, then validation is “short circuited” and the 2nd round of validations is not performed.

By default, all bean validation constraints are put into a “Default” group sequence. However, by putting a @GroupSequence on a class (like shown below) the “Default” group sequence is redefined just for that class. With the @GroupSequence on a class below, what it basically does is that during beans validation the 1st operation is to validate all constraints in the class that aren’t specifically assigned a group. That would be the @NotNull constraint first. If all of those are OK, then the 2nd operation is to validate all constraints that are in the Second.class group. That would be the @Size constraint. If all of those are OK, then 3rd operation is to validate all of the constraints that are in the Third.class group. That would be the @Pattern constraint. If at any time a group fails to validate, validation is “short circuited” and validation goes no farther.

Listing 6.1 - Bean to validate

package org.thoth.beanvalidation.groupsequence;

import javax.validation.GroupSequence;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Pattern;
import javax.validation.constraints.Size;

@GroupSequence({Candy.class, Candy.Second.class, Candy.Third.class})
public class Candy {

    protected interface Second {}
    protected interface Third {}

    private String name;

    @NotNull()
    @Size(min=4, max=10, groups = Second.class )
    @Pattern(regexp = "[a-z]", groups = Third.class)
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

Listing 6.2 - How to validate

package org.thoth.beanvalidation.groupsequence;

import java.util.Set;
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import static org.junit.Assert.assertEquals;
import org.junit.Before;
import org.junit.Test;

public class CandyTest {

    private Validator validator;

    @Before
    public void before() {
        validator = Validation.buildDefaultValidatorFactory().getValidator();
    }

    @Test
    public void short_circuits_first_if_null() {
        // setup
        Candy w = new Candy();

        // action
        Set<ConstraintViolation<Candy>> violations
            //= validator.validate(w, CheckGroupSequence.class);
            = validator.validate(w);

        // assert
        assertEquals(1, violations.size());
        assertEquals("may not be null", violations.iterator().next().getMessage());
    }


    @Test
    public void short_circut_if_size_is_in_violation() {
        // setup
        Candy w = new Candy();
        w.setName("foo");

        // action
        Set<ConstraintViolation<Candy>> violations
            = validator.validate(w);

        // assert
        assertEquals(1, violations.size());
        assertEquals("size must be between 4 and 10", violations.iterator().next().getMessage());
    }


    @Test
    public void short_circuit_if_pattern_is_in_violation() {
        // setup
        Candy w = new Candy();
        w.setName("SHRUBBERY");

        // action
        Set<ConstraintViolation<Candy>> violations
            = validator.validate(w);

        // assert
        assertEquals(1, violations.size());
        assertEquals("must match \"[a-z]\"", violations.iterator().next().getMessage());
    }
}

Summary

Beans validation is a powerful API, especially since it can be used within a Java EE server or in stand-alone Java SE applications. This is just a very short summary of the basics of the beans validation API, but, typically, it is enough to cover most questions developers have about how to use it.

Resolving SQLGrammarException using JPA @ManyToOne and @OneToMany Relationships

Abstract
So let's say your database has a simple parent-child relationship such as the relationship between a user and their addresses.  A single user can have many addresses so it is a one-to-many relationship from the point of view of the user; a many-to-one relationship from the point of view of the address.  You model this with JPA entities as follows:

Listing 1: User entity with collection of Address

@Entity
@Table(name = "app_user")
public class User implements Serializable {
    @EmbeddedId
    UserKey key;

    @OneToMany(mappedBy="user", fetch=FetchType.EAGER, cascade=CascadeType.ALL)
    Collection<Address> addresses;
}

In listing 1, you can see the @OneToMany annotation is used in the User class (#2) because from the point of view of a user, a user can have multiple addresses .  Recall this annotation is used on the owner of the relationship.

Listing 2: Address entity with parent User

@Entity
@Table(name = "app_address")
public class Address implements Serializable {
@EmbeddedId
    AddressKey key;

    @ManyToOne
    private User user;
}

In listing 2, the Address entity uses the @ManyToOne annotation (#2) because from the address point of view, an address can only have one user. That's it, real simple JPA config.

So after coding this up, you start your integration tests.  A test attempts to select data from the database and build a User/Address object tree. Immediately you run into a problem. The SQL generated is not valid and you get a SQLGrammarException complaining about some column which does not exist. listing 3 shows some of what the stack trace may say:

Listing 3: SQLGrammarException stack trace

javax.persistence.PersistenceException: org.hibernate.exception.SQLGrammarException: could not load an entity: 
  .
  .
  Caused by: org.hibernate.exception.SQLGrammarException: could not
  load an entity: [org.ferris.resolving.sqlgrammarexception.User#
  .
  .
  Caused by: java.sql.SQLSyntaxErrorException: Column
  'ADDRESSES1_.USER_BIRTHDAY' is either not in any table in the 
  FROM list or appears within a join specification and is outside
  the scope of the join specification or appears in a HAVING clause
  and is not in the GROUP BY list.

You look at this stack trace, you see Column 'ADDRESSES1_.USER_BIRTHDAY', and the $10,000 question is where is JPA getting this column? It doesn't exist in your database and none of your entities reference a column with this name.  You wired up your JPA entities with annotations in the exact way the book tells you to, so everything should work. Isn't that right?  The purpose of this article is to explore why you get this SQLGrammarException and how to resolve it.

System Requirements
The code was developed and run using the following system setup. If yours is different, it may work but no guarantees.

• JDK 1.7.0_17
• NetBeans 7.3.1
• Maven 3.0.5 (bundled with NetBeans)

The rest of the software dependencies can be found in the project's pom.xml. 

Download Project
If you just want to look at the project demonstrating the solution, download the code example from GitHub (https://github.com/mjremijan/JPATest).

Run Project
The project is a standard Maven setup.  Simply execute mvn. The project contains Maven integration tests which are NOT run during the unit testing phase of the Maven lifecycle. So executing mvn test won't run the example.

The code is configure so the integration tests will pass and you will not get the SQLGrammerException. You can mess around with the JPA annotations on your own an explore all the wonderful exceptions you can get.

Why the SQLGrammerException ?
To understand why you may be getting an SQLGrammarException, you really need to understand the difference between artificial and natural primary and foreign keys for database tables. It's in the keys that the problem lies.  So let's take a look at these keys.

When studying JPA, you learn the @ManyToOne and @OneToMany annotations can be used to establish a bi-directional relationship between entities. Typically, examples demonstrating how to code this relationship with JPA use very simple artificial primary and foreign keys. As a reminder, an artificial primary key is a column added to a database table which only exists to make rows in the table unique and as such is completely independent of the data stored in the table.  Artificial keys are typically Java long primitive values. Each table in the relationship typically has its own artificial key.  An artificial key relationship is shown in figure 1.

Figure 1: An artificial key database relationship 

Database relationships are sometimes this simple, but not often. This is especially true with legacy systems or any system which favors a natural primary and foreign keys.  As a reminder, a natural primary key specifies the column (or the combination of columns) of the data which make a row unique. A natural key relationship is shown in figure 2.

 Figure 2: A natural key database relationship

Natural keys are almost always a combination of columns because it's the combination of data that's needed to make the row unique. Using natural keys with multiple columns in JPA is not that difficult, but there are some challenges. If you don't do it right, you will get the SQLGrammarException. 

Now that you got a quick review of artificial and natural keys, let's take a look at how this is contributing to our problem. First look at the error message again.

Column 'ADDRESSES1_.USER_BIRTHDAY' is either not in any table. . .

ADDRESSES1 indicates the problem is with the Address entity. So that makes sense. Now referring back to listing 2, the Address entity has a relationship to its user by embedding the User entity like so:

    @ManyToOne
    private User user;
 

So the USER part of the error now kinda makes sense, but now what about BIRTHDAY? Well refer back to listing 1 and take a look at the properties of the User entity. It has an embedded UserKey as its primary key. Listing 4 shows UserKey.

Listing 4: UserKey is the primary key of  the User entity

@Embeddable
public class UserKey implements Serializable 
{
    private static final long serialVersionUID = 131374817387370831L;
    
    @Column(name = "last_name")
    private String lastName;

    @Column(name = "zip_code")
    private Long zipCode;

    @Column(name = "birthday")
    private Timestamp birthday;

    // getters and setters omitted for brevity

There is is! Inside UserKey is the missing BIRTHDAY. So now that it looks like we've identified all of the parts of the exception, let's walk though what's going on.

Address is an entity managed by JPA. As such, JPA scans through all the properties of Address looking for non-@Transient properties to manage. It finds the private User user property. Since User it is an object and not a simple primative, JPA uses make an intelligent guess about the column name for this property and assumes it starts with "user". Then JPA scans the User entity. In it, JPA finds @EmbeddedId UserKey userKey. Because UserKey is an embedded object, JPA now scans it for fields to manage and finds birthday. Putting this all together in hibernate-generated SQL you get ADDRESSES1_.USER_BIRTHDAY. Not very pretty, so what do we do about it?  We the solution is actually very simple.

Solution
To solve this problem, you need to configure JPA with the relationship between the entities. Recall the relationship between the user and address data is a complicated natural foreign key relationship. Figure 2 shows the primary key of App_User is a combination of LAST_NAME, ZIP, and BIRTHDAY.  For App_Address, these three columns are repeated with an addition of a fourth column to make the combination of LAST_NAME, ZIP, BIRTHDAY, and ADDRESS the primary key for App_Address. App_Address also uses its LAST_NAME, ZIP, and BIRTHDAY columns as a foreign key back to App_User. Though this may sound complicated, JPA annotations make it very easy. Listing 5 shows how to define the relationship in the Address entity.

Listing 5: Address relationship with its user

@ManyToOne(optional=false, fetch=FetchType.EAGER, cascade=CascadeType.ALL)
@JoinColumns({
    @JoinColumn(name="last_name", referencedColumnName="last_name", insertable=false, updatable=false),
    @JoinColumn(name="zip_code",  referencedColumnName="zip_code",  insertable=false, updatable=false),
    @JoinColumn(name="birthday",  referencedColumnName="birthday",  insertable=false, updatable=false)
})    
private User user;

In listing 5 @JoinColumn has been introduced (#3). The name property refers to the name of the column in the App_Address table.  The referencedColumnName propery refers to the name of the column in the App_User table. The insertable and updatable properties are self explanatory but critically important so JPA does not duplicate the columns when generating the INSERT and UPDATE statements. And that's it, very simple.


    

NetBeans and Public-Private SSH Key Access to CVS

Introduction
The purpose of this article is to document how to configure NetBeans to access a CVS repository over SSH using public-private keypairs.

Install "Putty" Applications
Putty is located at http://www.chiark.greenend.org.uk/~sgtatham/putty/.  The primary applications need are pageant.exe and plink.exe.

Run Pageant
Startup pageant.exe. It will be accessible via the system tray.

Right click on the pageant icon in the system tray to add the private key you use to access the CVS server.  Keep in mind that putty and all the putty related applications do not work with keys generated by the linux `ssh-keygen` command.  The private key generated by `ssh-keygen` needs to be opened with the puttygen.exe application and converted into a putty specific private key which can then be used in pageant.exe.

Configure NetBeans
Startup NetBeans.  Go to Team > Checkout.  For the CVS repository configuration, select the radio button to "Use External Shell".  In the "Shell Command" textbox, enter the fully qualified path to plink.exe. Click the "Next >" button and the CVS repository will be access via SSH using your public-private keypair.

That's it.  Enjoy!