JPA - @Column Examples

package com.logicbig.example;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class ExampleEntity {
    @Id
    @Column(name = "example_id")
    private String id;
    @Column(name = "example_String")
    private String myString;
    @Column(name = "example_integer")
    private int myInteger;
}

<?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="testPersistenceUnit" transaction-type="RESOURCE_LOCAL">
  <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
  <exclude-unlisted-classes>false</exclude-unlisted-classes>
  <properties>
   <property name="javax.persistence.schema-generation.database.action" value="create"/>
   <property name="javax.persistence.jdbc.url" value="jdbc:h2:mem:test;DB_CLOSE_DELAY=-1"/>
  </properties>
 </persistence-unit>
</persistence>

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.logicbig.example</groupId>
    <artifactId>jpa-column-annotation</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <version>1.4.193</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.persistence</groupId>
            <artifactId>eclipselink</artifactId>
            <version>2.6.4</version>
        </dependency>

        <dependency>
            <groupId>org.eclipse.persistence</groupId>
            <artifactId>javax.persistence</artifactId>
            <version>2.1.1</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.5.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

package com.logicbig.example;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;
import java.util.Arrays;
import java.util.List;

public class Main {
    private static final EntityManagerFactory emf =
            Persistence.createEntityManagerFactory(
                    "testPersistenceUnit");
    private static final EntityManager entityManager = emf.createEntityManager();

    public static void main(String[] args) {
        //this will print  column name, type, can-be-NULL,
        // KEY and default value  respectively
        runNativeQuery("SHOW COLUMNS from ExampleEntity");
    }

    private static void runNativeQuery(String s) {
        System.out.println("--------\n" + s);
        Query query = entityManager.createNativeQuery(s);
        List list = query.getResultList();
        for (Object o : list) {
            System.out.println(Arrays.toString((Object[]) o));
        }
    }
}

@Entity
public class Customer {
    @Id
    @GeneratedValue
    private int id;
    private String name;
    @ElementCollection
    @CollectionTable(name = "PHONES", joinColumns = @JoinColumn(name = "CUST_ID"))
    @Column(name = "PH_NO")
    private List<String> phoneNumbers;

    public String getName() {
        return name;
    }

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

    public List<String> getPhoneNumbers() {
        return phoneNumbers;
    }

    public void setPhoneNumbers(List<String> phoneNumbers) {
        this.phoneNumbers = phoneNumbers;
    }

    @Override
    public String toString() {
        return "Customer{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", phoneNumbers=" + phoneNumbers +
                '}';
    }
}

@Entity
public class Customer {
    @Id
    @GeneratedValue
    private int id;

    private String name;
    @ElementCollection
    @MapKeyColumn(name = "item")
    @Column(name = "qty")
    @CollectionTable(name = "ITEM_QTY")
    private Map<String, Integer> itemQtyMap;
    .............
}

@Entity
public class Customer {
    @Id
    @GeneratedValue
    private int id;
    private String name;

    @ElementCollection
    @CollectionTable(name = "ORDERS", joinColumns = @JoinColumn(name = "CUST_ID"))
    @Column(name = "ORDER_TYPE")
    private Map<Order, String> orders;
    .............
}

@Embeddable
public class Order {
    private String item;
    private int qty;
    private Date date;
    .............
}