向 JSF 2.0 UIInput 组件添加自定义属性 (HTML5) 支持

Question

我正在尝试编写一个渲染器来处理<h:inputText> 组件上的placeholder 属性。 在阅读JSF 2.0 strips out needed HTML5 attributes 之后，我走向了这条路，这似乎是正确的。这是我的自定义渲染器

public class InputRenderer extends com.sun.faces.renderkit.html_basic.TextRenderer{

    @Override
    public void encodeBegin(FacesContext context, UIComponent component) 
    throws IOException {
        System.out.println("Rendering :"+component.getClientId());

        String placeholder = (String)component.getAttributes().get("placeholder");
        if(placeholder != null) { 
            ResponseWriter writer = context.getResponseWriter();
            writer.writeAttribute("placeholder", placeholder, "placeholder");
        }

        super.encodeBegin(context, component);

    }


    @Override
    public void decode(FacesContext context, UIComponent component) {
        super.decode(context, component);
    }

    @Override
    public void encodeEnd(FacesContext context, UIComponent component) 
    throws IOException {
        super.encodeEnd(context, component);
    }
}

并且这个渲染器在 faces config 中注册为

 <render-kit>
    <renderer>
        <component-family>javax.faces.Input</component-family>
        <renderer-type>javax.faces.Text</renderer-type>
        <renderer-class>com.example.renderer.InputRenderer</renderer-class>
    </renderer>
</render-kit>

注册成功，没有问题。

我的意图是处理placeholder属性，插入它，然后将处理委托给super。我上面的代码不起作用，因为我在错误的地方插入了属性。它必须在writer.startElement('input') 执行后插入。但是，startElement 必须发生在 super 的 encodeBegin() 方法中的某处。那么如何插入自定义属性（本例中为“占位符”）然后继续执行流程？

注意：上面的代码确实添加了一个placeholder 属性，但没有添加到我打算添加的输入组件中，它会将其写入 Input 的父级（因为我试图在组件本身之前写入属性实际写在流中，它将属性应用到当前组件）

Answer 1

这是我的方式。我添加了占位符和数据主题属性。如果要添加更多属性，只需将其名称添加到属性数组即可。

import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
import javax.faces.context.ResponseWriter;

import com.sun.faces.renderkit.html_basic.TextRenderer;

public class InputRender extends TextRenderer {

    @Override
    protected void getEndTextToRender(FacesContext context,
            UIComponent component,
            String currentValue)
     throws java.io.IOException{

        String [] attributes = {"placeholder","data-theme"};

        ResponseWriter writer = context.getResponseWriter();

        for(String attribute : attributes)
        {
            String value = (String)component.getAttributes().get(attribute);
            if(value != null) {                             
                writer.writeAttribute(attribute, value, attribute);
            }
        }

        super.getEndTextToRender(context, component, currentValue);

    }

}

您应该将此添加到 faces-config.xml 文件中。

 <render-kit>
    <renderer>
        <component-family>javax.faces.Input</component-family>
        <renderer-type>javax.faces.Text</renderer-type>
        <renderer-class>your.package.InputRenderer</renderer-class>
    </renderer>
</render-kit>

Answer 2

你可以重写 ResponseWriters 的 startElement 方法，该方法只被调用一次，然后你可以恢复到原来的 responsewriter 对象。

import javax.faces.context.*;
import java.io.IOException;

public class InputRenderer extends com.sun.faces.renderkit.html_basic.TextRenderer{

      // Put all of the attributes you want to render here...
      private static final String[] ATTRIBUTES = {"required","placeholder"};

    @Override
    protected void getEndTextToRender(FacesContext context,
            UIComponent component, String currentValue) throws IOException {
        final ResponseWriter originalResponseWriter = context.getResponseWriter();
        context.setResponseWriter(new ResponseWriterWrapper() {

            @Override
// As of JSF 1.2 this method is now public.
            public ResponseWriter getWrapped() {
                return originalResponseWriter;
            }   

            @Override
            public void startElement(String name, UIComponent component)
                    throws IOException {
                super.startElement(name, component);
if ("input".equals(name)) {
  for (String attribute : ATTRIBUTES)
  {
    Object value = component.getAttributes().get(attribute);
    if (value != null)
    {
      super.writeAttribute(attribute,value,attribute);
} 
  }
}   
        });
        super.getEndTextToRender(context, component, currentValue);
        context.setResponseWriter(originalResponseWriter); // Restore original writer.
    }



}

Answer 3

并覆盖 MyFaces 2.0.8+

package com.hsop.abc.eld;

import java.io.IOException;

import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
import javax.faces.context.ResponseWriter;

import org.apache.myfaces.renderkit.html.HtmlTextRenderer;

public class InputRenderer extends HtmlTextRenderer
{
    @Override
    protected void renderInputBegin(FacesContext context, UIComponent component)
            throws IOException
    {
        // TODO Auto-generated method stub
        super.renderInputBegin(context, component);

    Object placeholder = component.getAttributes().get("placeholder");
    if(placeholder != null) { 
        ResponseWriter writer = context.getResponseWriter();
        writer.writeAttribute("placeholder", placeholder, "placeholder");
    }

    }
}