Tapestry Core

org.apache.tapestry5.corelib.components.AjaxFormLoop

A special form of the org.apache.tapestry5.corelib.components.Loop component that adds Ajax support to handle adding new rows and removing existing rows dynamically. Expects that the values being iterated over are entities that can be identified via a org.apache.tapestry5.PrimaryKeyEncoder. Works with org.apache.tapestry5.corelib.components.AddRowLink and org.apache.tapestry5.corelib.components.RemoveRowLink components.

[JavaDoc]

Component Parameters

Name	Type	Flags	Default	Default Prefix	Description
addRow	org.apache.tapestry5.Block	NOT Allow Null	block:defaultAddRow	literal	A block to render after the loop as the body of the org.apache.tapestry5.corelib.components.FormInjector. This typically contains a org.apache.tapestry5.corelib.components.AddRowLink.
context	Object	NOT Allow Null		prop	The context for the form loop (optional parameter). This list of values will be converted into strings and included in the URI. The strings will be coerced back to whatever their values are and made available to event handler methods.
element	String	NOT Allow Null		literal	The element to render for each iteration of the loop. The default comes from the template, or "div" if the template did not specify an element.
encoder	org.apache.tapestry5.PrimaryKeyEncoder	Required, NOT Allow Null		prop	Required parameter used to convert server-side objects (provided from the source) into client-side ids and back.
source	Iterable	Required, NOT Allow Null		prop	The objects to iterate over (passed to the internal Loop component).
value	Object	Required, NOT Allow Null		prop	The current value from the source.

Related Components

Examples

AjaxFormLoop renders an extensible, editable list of entities. It is intended for use with Master/Detail relationships (such as between an Order and a LineItem, in an e-commerce application). It allows new detail objects to be added on the server side, with corresponding new user interface added to the client side. Likewise, existing server-side objects can be removed, and the corresponding user interface also removed. AjaxFormLoop is dependent on the ability to extract an identifier (a primary key) from objects when rendering, and then retrieve the full object in a later request, such as when the form is submitted. This aligns well with an Object Relational Mapping layer such as Hibernate. This example has an address book of Persons, each of which has multiple Phones. It is, in fact, implemented in terms of Hibernate, using the tapestry-hibernate module.

Person.java

package org.example.addressbook.entities;

import org.apache.tapestry5.beaneditor.NonVisual;
import org.apache.tapestry5.beaneditor.Validate;
import org.apache.tapestry5.beaneditor.Width;
import org.apache.tapestry5.ioc.internal.util.CollectionFactory;

import javax.persistence.*;
import java.util.List;

@Entity
public class Person
{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @NonVisual
    private long id;

    . . .

    @OneToMany(mappedBy = "person", cascade = CascadeType.ALL)
    private List<Phone> phones = new ArrayList<Phone>();

    . . .

    public List<Phone> getPhones()
    {
        return phones;
    }

    public void setPhones(List<Phone> phones)
    {
        this.phones = phones;
    }
}

PhoneType.java

package org.example.addressbook.entities;

public enum PhoneType
{
    HOME, OFFICE, MOBILE, FAX, PAGER
}

Phone.java

package org.example.addressbook.entities;

import org.apache.tapestry5.beaneditor.NonVisual;
import org.apache.tapestry5.beaneditor.Validate;
import org.apache.tapestry5.beaneditor.Width;

import javax.persistence.*;

@Entity
public class Phone
{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @NonVisual
    private long id;

    @ManyToOne(optional = false)
    private Person person;

    private PhoneType type;

    @Column(nullable = true, length = 20)
    @Width(20)
    @Validate("required,maxlength=20")
    private String number;

    public long getId()
    {
        return id;
    }

    public void setId(long id)
    {
        this.id = id;
    }

    public Person getPerson()
    {
        return person;
    }

    public void setPerson(Person person)
    {
        this.person = person;
    }

    public PhoneType getType()
    {
        return type;
    }

    public void setType(PhoneType type)
    {
        this.type = type;
    }

    public String getNumber()
    {
        return number;
    }

    public void setNumber(String number)
    {
        this.number = number;
    }
}

Notice that the number field is nullable but required. This is because, when creating a new Phone instance, we have no number to fill in. However, a number is expected, and the user interface enforces that.

Edit.tml

<html xmlns:t="http://tapestry.apache.org/schema/tapestry_5_0_0.xsd">
  <body>
    <h1>Edit ${person.firstName} ${person.lastName}</h1>

    <t:form t:id="form">

      <t:errors/>

      <div class="t-beaneditor">

        <t:beaneditor t:id="person"/>

        <h2>Phones</h2>

        <div t:type="ajaxformloop" t:id="phones" source="person.phones" encoder="phoneEncoder" value="phone">
          <t:select t:id="type" value="phone.type"/>
          <t:textfield t:id="number" value="phone.number"/>

          |

          <t:removerowlink>remove</t:removerowlink>


        </div>

        <p>
          <input type="submit" value="Update"/>
        </p>
      </div>
    </t:form>

  </body>
</html>

Here we're editting the direct properties of the Person object and adding a section below to allow the phones for the person to be editted. The AjaxFormLoop looks much like a Loop component here, except we must provide a PrimaryKeyEncoder object.

Each row provides a RemoveRowLink component that will remove that row (from the server side, then on the client side).

The AjaxFormLoop provides a default row for adding additional data rows.

Edit.java

package org.example.addressbook.pages;

import org.apache.tapestry5.PrimaryKeyEncoder;
import org.apache.tapestry5.annotations.PageActivationContext;
import org.apache.tapestry5.annotations.Property;
import org.apache.tapestry5.hibernate.annotations.CommitAfter;
import org.apache.tapestry5.ioc.annotations.Inject;
import org.example.addressbook.entities.Person;
import org.example.addressbook.entities.Phone;
import org.hibernate.Session;

import java.util.List;

public class Edit
{
  @PageActivationContext
  @Property
  private Person person;

  @Property
  private Phone phone;

  @Inject
  private Session session;

  public PrimaryKeyEncoder<Long, Phone> getPhoneEncoder()
  {
    return new PrimaryKeyEncoder<Long, Phone>()
    {
      public Long toKey(Phone value)
      {
        return value.getId();
      }

      public void prepareForKeys(List<Long> keys)
      {
      }

      public Phone toValue(Long key)
      {
        return (Phone) session.get(Phone.class, key);
      }
    };
  }

  @CommitAfter
  public Object onSuccess()
  {
    return Index.class;
  }

  @CommitAfter
  Object onAddRowFromPhones()
  {
    Phone phone = new Phone();

    person.getPhones().add(phone);
    phone.setPerson(person);

    return phone;
  }

  @CommitAfter
  void onRemoveRowFromPhones(Phone phone)
  {
    session.delete(phone);
  }
}

The onAddRowFromPhones() event handler method's job is to add a new Phone instance and connect it to the Person. The @CommitAfter annotation ensures that changes are saved to the database (including generating a primary key for the new Phone instance).

The flip side is onRemoveRowFromPhones(), which is the event handler when removing a row. The event handler method is passed the Phone object to remove. Again, it is necessary to commit the Hibernate transaction.

The minimal implementation of a PrimaryKeyEncoder is also shown; this one is customized for Phone instances, and knows how to extract primary keys (the id property) and convert primary keys back into objects. This could easily be rolled out as a Tapestry IoC service.

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