在Tapestry中通用的property selection model

     Tapestry中构建选择列表需要使用IPropertySelectionModel，Model可以映射选择列表中的Label和Option，Tapestry中已经提供一个常用的StringSelectonModel,具体组件使用如下：<o:p></o:p>

Html代码<o:p></o:p>

 

Java代码

java 代码

public abstract class DetailsPage extends BasePage {

  public static final IPropertySelectionModel GENDER_MODEL =

      new StringPropertySelectionModel(new String[] { "Unspecified", "Female", "Male" });



  public abstract String getGender();



  public void formSubmit(IRequestCycle cycle) {

      // Process form submission

      String genderSelection = getGender();

      ...

  }

}

      开发中比较常见的选择列表就是类别的选择，，一般是新建一个类别的SelectionModel，例如如下代码

java 代码

public class TypeSelectionModel implements IPropertySelectionModel, Serializable {

  private List TypeList;



  public ItemSelectionModel(List typeList) {

      this. typeList = typeList;

  }



  public int getOptionCount() { return typeList.size(); }



  public Object getOption(int index) {

      return ((Type)typeList.get(index)).getId();

  }



  public String getLabel(int index) {

      return ((Type) typeList.get(index)).getName();

  }



  public String getValue(int index) { return Integer.toString(index); }



  public Object translateValue(String value) {

      return getOption(Integer.parseInt(value));

  }

}

这只是传统方法，开发中的类别如果多了，每一个都要新建一个SelectionModel。

下面是在Tapestry JumpStart里看到的通用的SelectionModel，感觉比较不错，现介绍给大家，具体代码如下：

java 代码

package com.javaeye.tapestrying.selectionModel;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import org.apache.tapestry.form.IPropertySelectionModel;

public class ObjectPropertySelectionModel implements IPropertySelectionModel {

       private List _list;

       private Method _methodToGetLabel = null;

       private Method _methodToGetOption = null;

       private boolean _allowNoSelection = false;

       private String _noSelectionMessage = null;

       private int _offset = 0;

       public ObjectPropertySelectionModel() {

              _list = new ArrayList();

              throw new UnsupportedOperationException("Do not use the default constructor.");

       }
       /**

        *

        * @param list

        *            the list of objects to represent in a PropertySelection

        *            component. WARNING: The objects in the list MUST implement

        *            equals(Object obj) and hashCode(), and if they are EJB3

        *            Entities those methods MUST return the same thing for

        *            different instances of the same detached entity (eg. by

        *            matching on Id only).

        * @param clazz

        *            the class of objects in the list.

        * @param nameOfMethodToGetLabel

        *            the name of the method that PropertySelection must invoke on

        *            each object in the list to get its label to display in the

        *            list on the page. For example, the method name might be

        *            "getShortName".

        * @param nameOfMethodToGetOption

        *            the name of the method that PropertySelection must invoke on

        *            an object when it has been selected. The result is put into

        *            the property named in the "value" parameter of the

        *            PropertySelection. For example, the method name might be

        *            "getKey". If you want the result to be the the whole object

        *            then set this argument to null.

        *

        */

       public ObjectPropertySelectionModel(Listextends Object> list, Class clazz, String nameOfMethodToGetLabel,

                     String nameOfMethodToGetOption) {              this(list, clazz, nameOfMethodToGetLabel, nameOfMethodToGetOption, false, null);

       }
       /**

        *

        * @param list

        *            the list of objects to represent in a PropertySelection

        *            component. WARNING: The objects in the list MUST implement

        *            equals(Object obj) and hashCode(), and if they are EJB3

        *            Entities those methods MUST return the same thing for

        *            different instances of the same detached entity (eg. by

        *            matching on Id only).

        * @param clazz

        *            the class of objects in the list.

        * @param nameOfMethodToGetLabel

        *            the name of the method that PropertySelection must invoke on

        *            each object in the list to get its label to display in the

        *            list on the page. For example, the method name might be

        *            "getShortName".

        * @param nameOfMethodToGetOption

        *            the name of the method that PropertySelection must invoke on

        *            an object when it has been selected. The result is put into

        *            the property named in the "value" parameter of the

        *            PropertySelection. For example, the method name might be

        *            "getKey". If you want the result to be the the whole object

        *            then set this argument to null.

        * @param allowNoSelection

        *            If true then adds an element to the start of the list. Its

        *            option is null.

        * @param noSelectionLabel

        *            If null then no label. A typical label might be "Select...".

        *

        */
       public ObjectPropertySelectionModel(Listextends Object> list, Class clazz, String nameOfMethodToGetLabel,

                     String nameOfMethodToGetOption, boolean allowNoSelection, String noSelectionLabel) {
              try {
                     _list = list;

                     _methodToGetLabel = clazz.getMethod(nameOfMethodToGetLabel, (Class[]) null);

                     if (nameOfMethodToGetOption != null) {

                            _methodToGetOption = clazz.getMethod(nameOfMethodToGetOption, (Class[]) null);
                     }
                     _allowNoSelection = allowNoSelection;

                     if (_allowNoSelection) {
                            _noSelectionMessage = noSelectionLabel;
                       _offset = 1;

                     }
              }
              catch (SecurityException e) {
                     throw new IllegalStateException(e);
              }
              catch (NoSuchMethodException e) {
                    throw new IllegalArgumentException("Given nameOfMethodToGetLabel=\"" + nameOfMethodToGetLabel + "\", nameOfMethodToGetOption=\""

                            + nameOfMethodToGetOption + "\", class=\"" + clazz + "\".", e);
              }
       }
       public int getOptionCount() {
              return _list.size() + _offset;
       }
       public Object getOption(int index) {
              if (_allowNoSelection) {
                     if (index < _offset) {
                            return null;
                     }
              }
              Object o = _list.get(index - _offset);
              if (_methodToGetOption == null) {
                     return o;
              }
              else {
                     try {
                            Object option = _methodToGetOption.invoke(o, (Object[]) null);
                            return option;
                     }
                     catch (IllegalArgumentException e) {
                            throw new IllegalStateException("Problem with the given methodToGetOption \"" + _methodToGetOption + "\": ", e);
                     }
                     catch (IllegalAccessException e) {
                            throw new IllegalStateException("Problem with the given methodToGetOption \"" + _methodToGetOption + "\": ", e);
                     }
                     catch (InvocationTargetException e) {
                            throw new IllegalStateException("Problem with the given methodToGetOption \"" + _methodToGetOption + "\": ", e);
                     }
              }
       }
       public String getLabel(int index) {
              if (_allowNoSelection) {
                     if (index < _offset) {
                            return _noSelectionMessage;
                     }
              }
              Object o = _list.get(index - _offset);
              try {
                     String label = _methodToGetLabel.invoke(o, (Object[]) null).toString();
                     return label;
              }
              catch (IllegalArgumentException e) {
                     throw new IllegalStateException("Problem with the given methodToGetLabel \"" + _methodToGetOption + "\": ", e);
              }
                catch (IllegalAccessException e) {
                     throw new IllegalStateException("Problem with the given methodToGetLabel \"" + _methodToGetOption + "\": ", e);
              }
              catch (InvocationTargetException e) {
                     throw new IllegalStateException   ("Problem with the given methodToGetLabel \"" + _methodToGetOption + "\": ", e);
              }
       }
      public String getValue(int index) {
              return Integer.toString(index);
       }
       public Object translateValue(String value) {
              return value == null ? null : getOption(Integer.parseInt(value));
       }
}

具体使用如下，假如现在有一个配件类型的类

java 代码

public class FittingType {
    private Long id;
    private String name;
    private Set<fitting></fitting> fittings = new HashSet<fitting></fitting>();
//getter and setter
}

<o:p></o:p>

创建配件类时，需要选择配件类型

java 代码

private IPropertySelectionModel fittingTypeSelectionModel;

public IPropertySelectionModel getFittingTypeSelectionModel() {

       if (fittingTypeSelectionModel == null) {

           List<fittingtype></fittingtype> fittingTypes = getFittingTypeService().findAll();

           fittingTypeSelectionModel = new ObjectPropertySelectionModel(

                  fittingTypes, FittingType.class, "getName", "getId", true,

                  "选择分类");
       }
       return fittingTypeSelectionModel;
    }
public abstract Long getFittingTypeId();
public ILink onSave() {
       //其他
       if (getFittingTypeId() != null) {

           fitting.setType(getFittingTypeService()

                  .findByID(getFittingTypeId()));

       }

       //其他
    }

Html中定义组件<o:p></o:p>

java 代码

"type@PropertySelection" model="ognl:fittingTypeSelectionModel" value="ognl:fittingTypeId" displayName="配件类型"/>

<o:p> </o:p>

具体定义中

fittingTypeSelectionModel = new ObjectPropertySelectionModel(<o:p></o:p>

                  fittingTypes, FittingType.class, "getName", "getId", true,<o:p></o:p>

                  "选择分类");<o:p></o:p>

       }<o:p></o:p>

参数1：候选的List

参数2：类别

参数3：label的getter方法

参数4：option的getter方法

参数5：是否允许没有选项

参数6：没有选项时的label

<o:p> </o:p>

好了，项目中又多了个通用的东西，开发时又可以 happy 了。

java 代码

"@PropertySelection" model="ognl:@com.myexample.DetailsPage@GENDER_MODEL" value="ognl:gender"/>