Java 通用 JSF 实体转换器
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Generic JSF entity converter
提问by retrodev
I'm writing my first Java EE 6 web app as a learning exercise. I'm not using a framework, just JPA 2.0, EJB 3.1 and JSF 2.0.
我正在编写我的第一个 Java EE 6 Web 应用程序作为学习练习。我没有使用框架，只是使用 JPA 2.0、EJB 3.1 和 JSF 2.0。
I have a Custom Converter to convert a JPA Entity stored in a SelectOne component back to an Entity. I'm using an InitialContext.lookup to obtain a reference to a Session Bean to find the relevant Entity.
我有一个自定义转换器将存储在 SelectOne 组件中的 JPA 实体转换回实体。我正在使用 InitialContext.lookup 来获取对会话 Bean 的引用以查找相关实体。
I'd like to create a generic Entity Converter so I don't have to create a converter per Entity. I thought I'd create an Abstract Entity and have all Entities extend it. Then create a Custom Converter for the Abstract Entity and use it as the converter for all Entities.
我想创建一个通用的实体转换器，这样我就不必为每个实体创建一个转换器。我以为我会创建一个抽象实体并让所有实体扩展它。然后为抽象实体创建一个自定义转换器，并将其用作所有实体的转换器。
Does that sound sensible and/or practicable?
这听起来合理和/或可行吗？
Would it make more sense not to have an abstract entity, just a converter that converts any entity? In that case I'm not sure how I'd obtain a reference to the appropriate Session Bean.
没有抽象实体，只有转换任何实体的转换器是否更有意义？在那种情况下，我不确定如何获得对适当会话 Bean 的引用。
I've included my current converter because I'm not sure I'm obtaining a reference to my Session Bean in the most efficient manner.
我已经包含了我当前的转换器，因为我不确定我是否以最有效的方式获得了对我的会话 Bean 的引用。
package com.mycom.rentalstore.converters;
import com.mycom.rentalstore.ejbs.ClassificationEJB;
import com.mycom.rentalstore.entities.Classification;
import javax.faces.application.FacesMessage;
import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
import javax.faces.convert.Converter;
import javax.faces.convert.ConverterException;
import javax.faces.convert.FacesConverter;
import javax.naming.InitialContext;
import javax.naming.NamingException;
@FacesConverter(forClass = Classification.class)
public class ClassificationConverter implements Converter {
private InitialContext ic;
private ClassificationEJB classificationEJB;
@Override
public Object getAsObject(FacesContext context, UIComponent component, String value) {
try {
ic = new InitialContext();
classificationEJB = (ClassificationEJB) ic.lookup("java:global/com.mycom.rentalstore_RentalStore_war_1.0-SNAPSHOT/ClassificationEJB");
} catch (NamingException e) {
throw new ConverterException(new FacesMessage(String.format("Cannot obtain InitialContext - %s", e)), e);
}
try {
return classificationEJB.getClassificationById(Long.valueOf(value));
} catch (Exception e) {
throw new ConverterException(new FacesMessage(String.format("Cannot convert %s to Classification - %s", value, e)), e);
}
}
@Override
public String getAsString(FacesContext context, UIComponent component, Object value) {
return String.valueOf(((Classification) value).getId());
}
}
采纳答案by rbento
Well I had the same problem today, and I solved it by creating a generic ConversionHelper and using it in the converter. For this purpose I have an EntityService which is a generic SLSB that I use to perform simple CRUD operations for any entity type. Also my entities implement a PersistentEntity interface, which has a getId and setId methods and I keep them with simple primary keys. That's it.
好吧，我今天遇到了同样的问题，我通过创建一个通用的 ConversionHelper 并在转换器中使用它来解决它。为此，我有一个 EntityService，它是一个通用的 SLSB，我用它来为任何实体类型执行简单的 CRUD 操作。我的实体也实现了一个 PersistentEntity 接口，它有一个 getId 和 setId 方法，我用简单的主键来保存它们。就是这样。
In the end my converter looks like this:
最后我的转换器看起来像这样：
@FacesConverter(value = "userConverter", forClass = User.class)
public class UserConverter implements Converter {
@Override
public Object getAsObject(FacesContext ctx, UIComponent component, java.lang.String value) {
return ConversionHelper.getAsObject(User.class, value);
}
@Override
public String getAsString(FacesContext ctx, UIComponent component, Object value) {
return ConversionHelper.getAsString(value);
}
}
And my conversion helper looks like this:
我的转换助手看起来像这样：
public final class ConversionHelper {
private ConversionHelper() {
}
public static <T> T getAsObject(Class<T> returnType, String value) {
if (returnType== null) {
throw new NullPointerException("Trying to getAsObject with a null return type.");
}
if (value == null) {
throw new NullPointerException("Trying to getAsObject with a null value.");
}
Long id = null;
try {
id = Long.parseLong(value);
} catch (NumberFormatException e) {
throw new ConverterException("Trying to getAsObject with a wrong id format.");
}
try {
Context initialContext = new InitialContext();
EntityService entityService = (EntityService) initialContext.lookup("java:global/myapp/EntityService");
T result = (T) entityService.find(returnType, id);
return result;
} catch (NamingException e) {
throw new ConverterException("EntityService not found.");
}
}
public static String getAsString(Object value) {
if (value instanceof PersistentEntity) {
PersistentEntity result = (PersistentEntity) value;
return String.valueOf(result.getId());
}
return null;
}
}
Now creating converters for simple JPA entities is a matter of duplicate a converter and change 3 parameters.
现在为简单的 JPA 实体创建转换器是一个复制转换器并更改 3 个参数的问题。
This is working well for me, but I don't know if it is the best approach in terms of style and performance. Any tips would be appreciated.
这对我来说效果很好，但我不知道这是否是风格和性能方面的最佳方法。任何提示将不胜感激。
回答by Ecmel Ercan
I am using JSF 2.0 view map:
我正在使用 JSF 2.0 视图地图：
@FacesConverter("entityConverter")
public class EntityConverter implements Converter {
private static final String key = "com.example.jsf.EntityConverter";
private static final String empty = "";
private Map<String, Object> getViewMap(FacesContext context) {
Map<String, Object> viewMap = context.getViewRoot().getViewMap();
@SuppressWarnings({ "unchecked", "rawtypes" })
Map<String, Object> idMap = (Map) viewMap.get(key);
if (idMap == null) {
idMap = new HashMap<String, Object>();
viewMap.put(key, idMap);
}
return idMap;
}
@Override
public Object getAsObject(FacesContext context, UIComponent c, String value) {
if (value.isEmpty()) {
return null;
}
return getViewMap(context).get(value);
}
@Override
public String getAsString(FacesContext context, UIComponent c, Object value) {
if (value == null) {
return empty;
}
String id = ((Persistent) value).getId().toString();
getViewMap(context).put(id, value);
return id;
}
}
回答by Craig Ringer
Use Seam Faces, it provides a Converter class that does what you want.
使用 Seam Faces，它提供了一个可以执行您想要的操作的 Converter 类。
org.jboss.seam.faces.conversion.Converter
org.jboss.seam.faces.conversion.Converter
While it's a JBoss project, Seam 3 works fine with Glassfish 3.1 and newer.
虽然它是一个 JBoss 项目，但 Seam 3 可以与 Glassfish 3.1 和更新版本配合使用。
http://seamframework.org/Seam3/FacesModule
http://seamframework.org/Seam3/FacesModule
On 3.1 it does have a couple of additional dependencies; see http://blog.ringerc.id.au/2011/05/using-seam-3-with-glassfish-31.html
在 3.1 上，它确实有几个额外的依赖项；见http://blog.ringerc.id.au/2011/05/using-seam-3-with-glassfish-31.html
回答by Anthony O.
To complete the response of Craig Ringer, you can use the generic org.jboss.seam.faces.conversion.ObjectConverterof the Seam 3 FacesModule.
要完成克雷格·林格的响应，你可以使用通用org.jboss.seam.faces.conversion.ObjectConverter的中缝3 FacesModule。
You can grab the code here : https://github.com/seam/faces/blob/develop/impl/src/main/java/org/jboss/seam/faces/conversion/ObjectConverter.java
你可以在这里获取代码：https: //github.com/seam/faces/blob/develop/impl/src/main/java/org/jboss/seam/faces/conversion/ObjectConverter.java
It uses 2 HashMaps (one is used reversly) and stocks its objects in the Conversation.
它使用 2HashMap秒（反向使用 1秒）并将其对象存储在Conversation.
回答by ichalos
Try this using Seam Facesfrom Seam 3.
使用Seam 3 中的Seam Faces试试这个。
@Named("DocTypeConverter")
public class DocumentTypeConverter implements Converter, Serializable {
private static final long serialVersionUID = 1L;
@Inject
private DocumentTypeSessionEJB proDocTypeSb;
@Override
public Object getAsObject(FacesContext context, UIComponent component,
String value) {
DocumentType result = null;
if (value != null && !value.trim().equals("")) {
try {
result = (DocumentType) proDocTypeSb.findById(DocumentType.class, value);
} catch(Exception exception) {
throw new ConverterException(new FacesMessage(FacesMessage.SEVERITY_ERROR, "Conversion Error", "Not a valid value"));
}
}
return result;
}
@Override
public String getAsString(FacesContext context, UIComponent component,
Object value) {
String result = null;
if (value != null && value instanceof DocumentType){
DocumentType docType = (DocumentType) value;
result = docType.getId();
}
return result;
}
}
回答by alexandrubarbat
my solution is the following :
我的解决方案如下：
@ManagedBean
@SessionScoped
public class EntityConverterBuilderBean {
private static Logger logger = LoggerFactory.getLogger(EntityConverterBuilderBean.class);
@EJB
private GenericDao dao;
public GenericConverter createConverter(String entityClass) {
return new GenericConverter(entityClass, dao);
}
}
public class GenericConverter implements Converter {
private Class clazz;
private GenericDao dao;
public GenericConverter(String clazz, Generic dao) {
try {
this.clazz = Class.forName(clazz);
this.dao = dao;
} catch (Exception e) {
logger.error("cannot get class: " + clazz, e);
throw new RuntimeException(e);
}
}
public Object getAsObject(javax.faces.context.FacesContext facesContext, javax.faces.component.UIComponent uiComponent, java.lang.String s) {
Object ret = null;
if (!"".equals(s)) {
Long id = new Long(s);
ret = dao.findById(clazz, id);
}
return ret;
}
public String getAsString(javax.faces.context.FacesContext facesContext, javax.faces.component.UIComponent uiComponent, java.lang.Object o) {
if (o != null) {
return ((SimpleEntity) o).getId() + "";
} else {
return "";
}
}
}
and in pages:
并在页面中：
<h:selectOneMenu id="x" value="#{controller.x}"
converter="#{entityConverterBuilderBean.createConverter('com.test.model.TestEntity')}">
回答by Xavier Dury
(UPDATED FOR JSF 2.3)
（针对 JSF 2.3 更新）
I am using something like this:
我正在使用这样的东西：
@FacesConverter(value = "entityConverter", managed = true)
public class EntityConverter implements Converter<Object> {
@Inject
private EntityManager entityManager;
@Override
public Object getAsObject(FacesContext context, UIComponent component, String value) {
Class<?> entityType = component.getValueExpression("value").getType(context.getELContext());
Class<?> idType = entityManager.getMetamodel().entity(entityType).getIdType().getJavaType();
Converter idConverter = context.getApplication().createConverter(idType);
Object id = idConverter.getAsObject(context, component, value);
return entityManager.getReference(entityType, id);
}
@Override
public String getAsString(FacesContext context, UIComponent component, Object value) {
Object id = entityManager.getEntityManagerFactory().getPersistenceUnitUtil().getIdentifier(value);
Converter idConverter = context.getApplication().createConverter(id.getClass());
return idConverter.getAsString(context, component, id);
}
}
In template, use <f:converter binding="#{entityConverter}" />.
在模板中，使用<f:converter binding="#{entityConverter}" />.
