在JSF中将inputText转换为byte [] [英] Convert inputText to byte[] in JSF

问题描述

我正在编写一个Web应用程序，它有一个JSF页面，并在其后面有一个bean。我遇到了麻烦，我认为这是因为这个bean需要一个字节数组用于一个特定的字段，并且它提供了一个字符串。

据我所知， JSF提供了一些功能，可以自动将您在inputText字段中输入的内容转换为所需的数据类型，但是当您需要一个字节[]时，我认为它不会执行此操作...

这仅仅是为JSF编写客户转换器的问题吗？比如像这样：

  public class StringToByteArray implements Converter {
 
 ... 
 
 public byte [] getAsObject（FacesContext context，UIComponent component，String value）{
 if（StringUtils.isEmpty（value））{return null;} 
 
 byte [] valueAsBytes = new byte []; 
 
 valueAsBytes = value.getBytes（）; 
 
返回valueAsBytes; }} 
  

解决方案

答案是肯定的。这只是写一个自定义转换器的问题。不要因为认为代码太简单了而感到气馁。以下是将自定义对象转换为字符串并返回的转换器的示例。这种转换器通常用于选择菜单：

  @FacesConverter（value =merkmalConverter）
 public class MerkmalMenuConverter实现了Converter {
 
 public String getAsString（FacesContext context，UIComponent component，Object value）{
 if（value！= null）{
 Merkmal m =（Merkmal）value; 
 return m.getBezeichnung（）; 
} 
返回null; //值为空。 
 
 $ b @SuppressWarnings（unchecked）
 public Object getAsObject（FacesContext context，UIComponent component，String value）{
 if（value！= null）{ 
 MerkmalJpaController mJpaC = new MerkmalJpaController（）; 
列表< Merkmal> mList = mJpaC.findMerkmalEntities（）; （Merkmal m：mList）{
 if（m.getBezeichnung（）。equals（value））{
 return m; 
} 
} 
} 
返回null; //值为空或没有任何匹配。 
 
 
 
 
 $ b $使用你的转换器在jsf文件中显示如下 
 
 
 < f：converter converterId =merkmalConverter/> 
  
 
I'm writing a web application which has a JSF page with a bean behind it. I am having trouble with it and I think it's because the bean is expecting a byte array for one particular field and it's being provided with a String.

From what I understand, JSF provides some functionality to automatically convert whatever you enter in your inputText fields to the required data type, but I don't think it does this when you want a byte[] ...

Is it simply a matter of writing a customer converter for JSF? Such as something like this:
public class StringToByteArray implements Converter {

...

public byte[] getAsObject(FacesContext context, UIComponent component, String value) {
    if (StringUtils.isEmpty(value)){ return null;}

    byte[] valueAsBytes = new byte[];

    valueAsBytes = value.getBytes();

    return valueAsBytes; } } 

解决方案
The answer is yes. It is simply the matter of writing a custom converter. Don´t be discouraged by thinking "too much code for a simple conversion". Here is an example for a converter that converts a custom object to string and back. This kind of converter is often used for select menus:
@FacesConverter( value="merkmalConverter" )
public class MerkmalMenuConverter implements Converter {

    public String getAsString(FacesContext context, UIComponent component, Object value) {
        if (value != null) {
            Merkmal m = (Merkmal) value;
            return m.getBezeichnung();
        }
        return null; // Value is null.
    }

    @SuppressWarnings("unchecked")
    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        if (value != null) {
            MerkmalJpaController mJpaC = new MerkmalJpaController();
            List<Merkmal> mList = mJpaC.findMerkmalEntities();
            for (Merkmal m : mList) {
                if (m.getBezeichnung().equals(value)) {
                    return m;
                }
            }
        }
        return null; // Value is null or doesn't have any match.
    }
}
Use your converter in the jsf file as shown here as child element of your input field to be converted:
<f:converter converterId="merkmalConverter" />


                        
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