SpringMVC复选框：自定义绑定/ PropertyEditor对自定义类型的支持

问题描述

这确实很简单，但是我找不到很好的例子：

It's something really simple but I couldn't find a good example:

我有一个自定义数据类型，希望绑定到SpringMVC复选框，它看起来像这样：是/否：

I have a custom data type that I'd like to bind to a SpringMVC checkbox, it looks like this: YES/NO:

public enum YesNoDataType {
   YES("Yes"), 
   NO("No");
}

SpringMVC复选框自动映射为布尔值，现在我需要映射Selected->是的，Empty-> NO。

SpringMVC checkboxes auto-map to Booleans, now I need to map Selected->YES, Empty->NO.

我知道我必须实现这4个PropertyEditorSupport方法之一，但是哪种方法又如何实现？

I know I have to implement one of these 4 PropertyEditorSupport methods, but which ones, and how?

<form:checkbox path="testYesNo"></form:checkbox>

模型

private YesNoDataType testYesNo; 

控制器

binder.registerCustomEditor(YesNoDataType.class, new PropertyEditorSupport() {

          // Which ones to override?

            @Override
            public void setValue(Object value) {
                // TODO Auto-generated method stub
                super.setValue(value);
            }

            @Override
            public Object getValue() {
                // TODO Auto-generated method stub
                return super.getValue();
            }

            @Override
            public String getAsText() {
                // TODO Auto-generated method stub
                return super.getAsText();
            }

            @Override
            public void setAsText(String text) throws IllegalArgumentException {
                // TODO Auto-generated method stub
                super.setAsText(text);
            }

});

推荐答案

我尝试定义和注册一些转换器（YesNoDataType / Boolean ），但我在SpringMVC的CheckboxTag.java中看到它们都是无用的。没有任何转换器或绑定调整将起作用，因为该标记仅显式检查布尔值和字符串：

I tried defining and registering some Converters (YesNoDataType / Boolean), but I see in SpringMVC's CheckboxTag.java that they're all useless. No converters or binding tweaks will work because the tag explicitly checks for Booleans and Strings only:

protected void writeTagDetails(TagWriter tagWriter) throws JspException {
    tagWriter.writeAttribute("type", getInputType());

    Object boundValue = getBoundValue();
    Class<?> valueType = getBindStatus().getValueType();

    if (Boolean.class.equals(valueType) || boolean.class.equals(valueType)) {
        // the concrete type may not be a Boolean - can be String
        if (boundValue instanceof String) {
            boundValue = Boolean.valueOf((String) boundValue);
        }
        Boolean booleanValue = (boundValue != null ? (Boolean) boundValue : Boolean.FALSE);
        renderFromBoolean(booleanValue, tagWriter);
    }

    else {
        Object value = getValue();
        if (value == null) {
            throw new IllegalArgumentException("Attribute 'value' is required when binding to non-boolean values");
        }
        Object resolvedValue = (value instanceof String ? evaluate("value", value) : value);
        renderFromValue(resolvedValue, tagWriter);
    }
}

字符串绑定与我无关。在 getValue（）字符串绑定（第2条）中，如果其 value = 属性被选中匹配模型中的字符串。我需要的是True / False布尔绑定，但是我的Converter需要插入第1章，才能从自定义类型获取布尔值。当您尝试超出常见的狭窄参数范围时，Spring如此严格的限制令我非常沮丧。问题仍然悬而未决。

The String binding is irrelevant to me. In the getValue() String binding (Clause #2), a checkbox is selected if its value="" attribute matches the string in the model. What I need is a True/False boolean binding, but my Converter needs to be plugged into Clause #1 to obtain a Boolean from a custom type. Just very frustrated that Spring is so restrictive as soon as you try to go outside the narrow parameters of what's common. The issue is still outstanding.

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