Step 4 Domain Classes - Learn JBStrap

Supplier

First, create the supplier class. This table does not reference any tables, so this one should be the last one when creating a chain of references and no other classes need to be there in the code in order to create it.

        package com.jbstrap.example.domain;
 
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
 
/**
 * Entity class for SUPPLIER database table
 */
@Entity
public class Supplier {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", updatable = false, nullable = false)
    private Long id;
 
    @Column(name="company_name")
    private String companyName;
 
    @Column(name="contact_name")
    private String contactName;
 
    private String city;
    private String country;
    private String phone;
    private String fax;
 
    public Long getId() {
        return id;
    }
 
    public void setId(final Long id) {
        this.id = id;
    }
 
    public String getCompanyName() {
        return companyName;
    }
 
    public void setCompanyName(final String companyName) {
        this.companyName = companyName;
    }
 
    public String getContactName() {
        return contactName;
    }
 
    public void setContactName(final String contactName) {
        this.contactName = contactName;
    }
 
    public String getCity() {
        return city;
    }
 
    public void setCity(final String city) {
        this.city = city;
    }
 
    public String getCountry() {
        return country;
    }
 
    public void setCountry(final String country) {
        this.country = country;
    }
 
    public String getPhone() {
        return phone;
    }
 
    public void setPhone(final String phone) {
        this.phone = phone;
    }
 
    public String getFax() {
        return fax;
    }
 
    public void setFax(final String fax) {
        this.fax = fax;
    }
 
}
       

The above example shows that this is a simple POJO class whose fields correspond to a database table field of the same name. When creating the domain class, you have to use conventional JPA annotations. The JBStrap framework uses the conventional JPA solution to access the data.

Product

Next, create the Product domain class. This class represents the PRODUCT database table. The above image shows the ‘product’ table referencing the ‘supplier’ table, that is, each product has a specified supplier. This relationship is also represented in the domain class, meaning that you must have a supplier class before creating the product class. With this being done, you can use the @ManyToOne annotation and its settings provided by the conventional JPA to create a data relationship.

        package com.jbstrap.example.domain;
 
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
 
import org.eclipse.persistence.annotations.JoinFetch;
import org.eclipse.persistence.annotations.JoinFetchType;
 
/**
 * Entity class for PRODUCT database table
 */
@Entity
public class Product {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", updatable = false, nullable = false)
    private Long id;
 
    @Column(name="product_name")
    private String productName;
 
    @Column(name="supplier_id")
    private Long supplierId;
 
    @ManyToOne
    @JoinFetch(JoinFetchType.OUTER)
    @JoinColumn(name="supplier_id", insertable=false, updatable=false)
    private Supplier supplier;
 
    @Column(name="unit_price")
    private Double unitPrice;
 
    @Column(name="package")
    private String packing;
 
    @Column(name="discontinued")
    private String discontinued;
 
    public Long getId() {
        return id;
    }
 
    public void setId(final Long id) {
        this.id = id;
    }
 
    public String getProductName() {
        return productName;
    }
 
    public void setProductName(final String productName) {
        this.productName = productName;
    }
 
    public Long getSupplierId() {
        return supplierId;
    }
 
    public void setSupplierId(final Long supplierId) {
        this.supplierId = supplierId;
    }
 
    public Double getUnitPrice() {
        return unitPrice;
    }
 
    public void setUnitPrice(final Double unitPrice) {
        this.unitPrice = unitPrice;
    }
 
    public String getPacking() {
        return packing;
    }
 
    public void setPacking(final String packing) {
        this.packing = packing;
    }
 
    public String getDiscontinued() {
        return discontinued;
    }
 
    public void setDiscontinued(final String discontinued) {
        this.discontinued = discontinued;
    }
 
}
       

In the above source code, there is a field that is not included in the database. This is the supplier field. You can see that the type of the field is the Supplier class created in the previous step, that is, the field contains an entire supplier record. As a result of this, if you retrieve a record from the product table, it returns not only its own data values, but also the corresponding supplier values are automatically retrieved, making all data accessible through the Product class.

Customer

Create the Customer class that corresponds to the CUSTOMER table. This domain class is a simple POJO class that does not contain any other references.

        package com.jbstrap.example.domain;
 
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
 
/**
 * Entity class for CUSTOMER database table
 */
@Entity
public class Customer {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", updatable = false, nullable = false)
    private Long id;
 
    @Column(name="first_name")
    private String firstName;
 
    @Column(name="last_name")
    private String lastName;
 
    private String city;
 
    private String country;
 
    private String phone;
 
    public Long getId() {
        return id;
    }
 
    public void setId(final Long id) {
        this.id = id;
    }
 
    public String getFirstName() {
        return firstName;
    }
 
    public void setFirstName(final String firstName) {
        this.firstName = firstName;
    }
 
    public String getLastName() {
        return lastName;
    }
 
    public void setLastName(final String lastName) {
        this.lastName = lastName;
    }
 
    public String getCity() {
        return city;
    }
 
    public void setCity(final String city) {
        this.city = city;
    }
 
    public String getCountry() {
        return country;
    }
 
    public void setCountry(final String country) {
        this.country = country;
    }
 
    public String getPhone() {
        return phone;
    }
 
    public void setPhone(final String phone) {
        this.phone = phone;
    }
 
}
       

Orders

Next, create the Orders class that contains order details. The above image shows that the ORDERS table references the CUSTOMER table. This reference should be included in the Orders class the same way you did for the Product class.

        package com.jbstrap.example.domain;
 
import java.util.Date;
 
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
 
import org.eclipse.persistence.annotations.JoinFetch;
import org.eclipse.persistence.annotations.JoinFetchType;
 
/**
 * Entity class for ORDERS database table
 */
@Entity
public class Orders {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", updatable = false, nullable = false)
    private Long id;
 
    @Column(name="order_date")
    @Temporal(TemporalType.DATE)
    private Date orderDate;
 
    @Column(name="order_number")
    private String orderNumber;
 
    @Column(name="customer_id")
    private Long customerId;
 
    @ManyToOne
    @JoinFetch(JoinFetchType.OUTER)
    @JoinColumn(name="customer_id", insertable=false, updatable=false)
    private Customer customer;
 
    @Column(name="total_amount")
    private Double totalAmount;
 
    @Column(name="status")
    private String status;
 
    public Long getId() {
        return id;
    }
 
    public void setId(final Long id) {
        this.id = id;
    }
 
    public Date getOrderDate() {
        return orderDate;
    }
 
    public void setOrderDate(final Date orderDate) {
        this.orderDate = orderDate;
    }
 
    public String getOrderNumber() {
        return orderNumber;
    }
 
    public void setOrderNumber(final String orderNumber) {
        this.orderNumber = orderNumber;
    }
 
    public Long getCustomerId() {
        return customerId;
    }
 
    public void setCustomerId(final Long customerId) {
        this.customerId = customerId;
    }
 
    public Customer getCustomer() {
        return customer;
    }
 
    public void setCustomer(final Customer customer) {
        this.customer = customer;
    }
 
    public Double getTotalAmount() {
        return totalAmount;
    }
 
    public void setTotalAmount(final Double totalAmount) {
        this.totalAmount = totalAmount;
    }
 
    public String getStatus() {
        return status;
    }
 
    public void setStatus(final String status) {
        this.status = status;
    }
 
}
       

OrderItems

As the last step, create the OrderItems class. This class represents the ORDER_ITEMS table that connects orders with the ordered items. This table is a cross-reference table between ORDERS and PRODUCT.

Based on what we learned above, the OrderItems class should reference the Orders and Product classes. For the purpose of this project it is better if we include only one of the references in the OrderItems domain class. The reason for this is that there is no part of the code that retrieves orders based on the products. In every case, ordered items are retrieved based on the order itself and so the OrderItems class has to reference the Product class only.

        package com.jbstrap.example.domain;
 
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
 
import org.eclipse.persistence.annotations.JoinFetch;
import org.eclipse.persistence.annotations.JoinFetchType;
 
/**
 * Entity class for ORER_ITEMS database table
 */
@Entity
@Table(name="order_items")
public class OrderItems {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", updatable = false, nullable = false)
    private Long id;
 
    @Column(name="order_id")
    private Long orderId;
 
    @Column(name="product_id")
    private Long productId;
 
    @Column(name="unit_price")
    private Double unitPrice;
 
    @Column(name="quantity")
    private Long quantity;
 
    @ManyToOne
    @JoinFetch(JoinFetchType.OUTER)
    @JoinColumn(name="product_id", insertable=false, updatable=false)
    private Product product;
 
    public Long getId() {
        return id;
    }
 
    public void setId(final Long id) {
        this.id = id;
    }
 
    public Long getOrderId() {
        return orderId;
    }
 
    public void setOrderId(final Long orderId) {
        this.orderId = orderId;
    }
 
    public Long getProductId() {
        return productId;
    }
 
    public void setProductId(final Long productId) {
        this.productId = productId;
    }
 
    public Double getUnitPrice() {
        return unitPrice;
    }
 
    public void setUnitPrice(final Double unitPrice) {
        this.unitPrice = unitPrice;
    }
 
    public Long getQuantity() {
        return quantity;
    }
 
    public void setQuantity(final Long quantity) {
        this.quantity = quantity;
    }
 
    public Product getProduct() {
        return product;
    }
 
    public void setProduct(final Product product) {
        this.product = product;
    }
 
}
       

Once you have created the data sources, you only need to register them in the JPA layer, so that they can work as separate entities. To do this, you only need to open the previously created persistence.xml file and add the classes to the persistence unit part in that file. Once done, this should look like the following:

        <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="ApplicationPU" transaction-type="RESOURCE_LOCAL">
        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
         
        <class>com.jbstrap.example.domain.Customer</class>
        <class>com.jbstrap.example.domain.Orders</class>
        <class>com.jbstrap.example.domain.Product</class>
        <class>com.jbstrap.example.domain.OrderItems</class>
        <class>com.jbstrap.example.domain.Supplier</class>

		<exclude-unlisted-classes>false</exclude-unlisted-classes>
        <shared-cache-mode>NONE</shared-cache-mode>
 
        <properties>
            <property name="show-sql" value="true" />
            <property name="eclipselink.weaving" value="false" />
            <property name="eclipselink.logging.level" value="FINE" />
            <property name="eclipselink.logging.parameters" value="true" />
            <property name="eclipselink.orm.throw.exceptions" value="true" />
            <property name="eclipselink.logging.logger" value="DefaultLogger" />
            <property name="eclipselink.logging.level.sql" value="FINEST" />
            <property name="eclipselink.refresh.cascade" value="NoCascading" />
            <property name="eclipselink.jdbc.cache-statements" value="false" />
            <property name="javax.persistence.jdbc.driver" value="org.hsqldb.jdbc.JDBCDriver" />
            <property name="javax.persistence.jdbc.url" value="jdbc:hsqldb:file:${basedir}/db/omdb.db;hsqldb.lock_file=false" /> 
            <property name="javax.persistence.jdbc.user" value="SA"/>
            <property name="javax.persistence.jdbc.password" value=""/>
            <property name="eclipselink.target-database" value="HSQL"/>
        </properties>
    </persistence-unit>
     
</persistence>
       

You can see that all previously created domain classes are listed within the ‘persistence tag’ between separate ‘class’ tags. This ensures that the persistence layer uses the classes to store the retrieved data.