Spring MVC类型转换：PropertyEditor或Converter？ [英] Spring MVC type conversion : PropertyEditor or Converter?
问题描述
我正在寻找在Spring MVC中绑定和转换数据的最简单和最简单的方法。如果可能，不做任何xml配置。
到目前为止，我一直在使用 PropertyEditors ，如下所示：
public class CategoryEditor extends PropertyEditorSupport {
//将字符串转换为类别（提交表单时）
@Override
public void setAsText（String text）{
类别c =新类别（文字）;
this.setValue（c）;
}
//将类别转换为字符串（显示窗体时）
@Override
public String getAsText（）{
类别c =类别）this.getValue（）;
return c.getName（）;
}
}
和
...
public class MyController {
@InitBinder
public void initBinder（WebDataBinder binder） {
binder.registerCustomEditor（Category.class，new CategoryEditor（））;
}
...
}
很简单：两个转换都在同一个类中定义，绑定是直接的。如果我想在所有控制器上执行一般绑定，我仍然可以添加我的xml配置中的3行。
但是Spring 3.x引入了一种新的方式来实现，使用转换器：
在一个Spring容器中，该系统可以用作替代
到PropertyEditors
所以让我们想使用转换器，因为它是最新的替代方案。我必须创建两个转换器：
public class StringToCategory implements Converter< String，Category> {
@Override
public类别转换（String source）{
类别c =新类别（来源）;
return c;
}
}
public class CategoryToString实现转换器< Category，String> {
@Override
public String convert（Category source）{
return source.getName（）;
}
}
第一个缺点： / strong>我必须做两个班。好处：不需要投票感谢一般性。
那么，如何简单的数据绑定转换器？
第二个缺点：我没有发现任何简单的方法（注释或其他程序设施）在控制器中执行： code> someSpringObject.registerCustomConverter（...）; 。
我发现的唯一方法是乏味，不简单，并且只涉及一般的交叉控制器绑定：
-
< bean id =conversionService
class =org.springframework.context.support.ConversionServiceFactoryBean>
< property name =converters>
< set>
< bean class =somepackage.StringToCategory/>
< bean class =somepackage.CategoryToString/>
< / set>
< / property>
< / bean>
-
Java config （仅限于Spring 3.1 + ）：
@EnableWebMvc
@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
@Override
protected void addFormatters（FormatterRegistry registry）{
registry.addConverter（new StringToCategory（））;
registry.addConverter（new CategoryToString（））;
}
}
由于所有这些缺点，为什么要使用Converters？我缺少什么？有没有其他的技巧，我不知道？
我很想继续使用PropertyEditors ...绑定更容易和更快。
由于所有这些缺点，为什么要使用Converters？我是否缺少
的东西？有没有其他的技巧，我不知道？
不，我想你有非常全面地描述PropertyEditor和转换器，一个被声明和注册。在我看来，PropertyEditor的范围是有限的 - 它们有助于将String转换为类型，这个字符串通常来自UI，因此使用@InitBinder注册PropertyEditor，使用WebDataBinder是有道理的。
另一方面，转换器更为通用，它适用于系统中的任何转换 - 而不仅仅是与UI相关的转换（字符串到目标类型）。例如，Spring Integration使用一个转换器广泛地将消息有效载荷转换为所需的类型。
我认为对于UI相关的流PropertyEditor仍然适用于您需要为特定的命令属性做一些自定义的操作。对于其他情况，我将采用Spring引用的建议，并写一个转换器（例如，从Long id转换为实体，作为示例）。
I am looking for the easiest and simplest way to bind and convert data in Spring MVC. If possible, without doing any xml configuration.
So far I've been using PropertyEditors like so :
public class CategoryEditor extends PropertyEditorSupport {
// Converts a String to a Category (when submitting form)
@Override
public void setAsText(String text) {
Category c = new Category(text);
this.setValue(c);
}
// Converts a Category to a String (when displaying form)
@Override
public String getAsText() {
Category c = (Category) this.getValue();
return c.getName();
}
}
and
...
public class MyController {
@InitBinder
public void initBinder(WebDataBinder binder) {
binder.registerCustomEditor(Category.class, new CategoryEditor());
}
...
}
It is simple : both conversion are defined in the same class, and the binding is straightforward. If I wanted to do a general binding across all my controllers, I could still add 3 lines in my xml config.
But Spring 3.x introduced a new way to do it, using Converters :
Within a Spring container, this system can be used as an alternative to PropertyEditors
So let's say I want to use Converters because it is "the latest alternative". I would have to create two converters :
public class StringToCategory implements Converter<String, Category> {
@Override
public Category convert(String source) {
Category c = new Category(source);
return c;
}
}
public class CategoryToString implements Converter<Category, String> {
@Override
public String convert(Category source) {
return source.getName();
}
}
First drawback : I have to make two classes. Benefit : no need to cast thanks to genericity.
Then, how do I simply data bind the converters ?
Second drawback : I haven't found any simple way (annotations or other programmatic facilities) to do it in a controller : nothing like someSpringObject.registerCustomConverter(...);.
The only ways I've found would be tedious, not simple, and only about general cross-controller binding :
<bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean"> <property name="converters"> <set> <bean class="somepackage.StringToCategory"/> <bean class="somepackage.CategoryToString"/> </set> </property> </bean>Java config (only in Spring 3.1+) :
@EnableWebMvc @Configuration public class WebConfig extends WebMvcConfigurerAdapter { @Override protected void addFormatters(FormatterRegistry registry) { registry.addConverter(new StringToCategory()); registry.addConverter(new CategoryToString()); } }
With all these drawbacks, why using Converters ? Am I missing something ? Are there other tricks that I am not aware of ?
I am tempted to go on using PropertyEditors... Binding is much easier and quicker.
With all these drawbacks, why using Converters ? Am I missing something ? Are there other tricks that I am not aware of ?
No, I think you have very comprehensively described both PropertyEditor and Converter, how each one is declared and registered.
In my mind, PropertyEditors are limited in scope - they help convert String to a type, and this string typically comes from UI, and so registering a PropertyEditor using @InitBinder and using WebDataBinder makes sense.
Converter on the other hand is more generic, it is intended for ANY conversion in the system - not just for UI related conversions(String to target type). For eg, Spring Integration uses a converter extensively for converting a message payload to a desired type.
I think for UI related flows PropertyEditors are still appropriate especially for the case where you need to do something custom for a specific command property. For other cases, I would take the recommendation from Spring reference and write a converter instead(for eg, to convert from a Long id to an entity say, as a sample).
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