springMVC 类型转换

一、使用注解式控制器注册PropertyEditor(针对具体的controller类处理)

1、使用WebDataBinder进行控制器级别的注册PropertyEditor(控制器独享)

@InitBinder
// 此处的参数也可以是ServletRequestDataBinder类型
public void initBinder(WebDataBinder binder) throws Exception {
	// 注册自定义的属性编辑器
	// 1、日期
	DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
	//CustomDateEditor类是系统内部自带的类
	CustomDateEditor dateEditor = new CustomDateEditor(df, true);
	// 表示如果命令对象有Date类型的属性，将使用该属性编辑器进行类型转换
	binder.registerCustomEditor(Date.class, dateEditor);
	// 自定义的电话号码编辑器(和【4.16.1、数据类型转换】一样)
	binder.registerCustomEditor(PhoneNumberModel.class, new PhoneNumberEditor());
}

 备注：转换对象必须要实现PropertyEditor接口，例如CustomDateEditor类

package org.springframework.beans.propertyeditors;

import java.beans.PropertyEditorSupport;
import java.text.DateFormat;
import java.text.ParseException;
import java.util.Date;
import org.springframework.util.StringUtils;

public class CustomDateEditor extends PropertyEditorSupport {

	private final DateFormat dateFormat;
	private final boolean allowEmpty;
	private final int exactDateLength;
	
	public CustomDateEditor(DateFormat dateFormat, boolean allowEmpty) {
		this.dateFormat = dateFormat;
		this.allowEmpty = allowEmpty;
		exactDateLength = -1;
	}

	public CustomDateEditor(DateFormat dateFormat, boolean allowEmpty, int exactDateLength) {
		this.dateFormat = dateFormat;
		this.allowEmpty = allowEmpty;
		this.exactDateLength = exactDateLength;
	}

	public void setAsText(String text) throws IllegalArgumentException {
		if (allowEmpty && !StringUtils.hasText(text)) {
			setValue(null);
		} else {
			if (text != null && exactDateLength >= 0 && text.length() != exactDateLength)
				throw new IllegalArgumentException((new StringBuilder("Could not parse date: it is not exactly")).append(exactDateLength).append("characters long").toString());
			try {
				setValue(dateFormat.parse(text));
			} catch (ParseException ex) {
				throw new IllegalArgumentException((new StringBuilder("Could not parse date: ")).append(ex.getMessage()).toString(), ex);
			}
		}
	}

	public String getAsText() {
		Date value = (Date) getValue();
		return value == null ? "" : dateFormat.format(value);
	}

}

2、使用xml配置实现类型转换(系统全局转换器)

（1、注册ConversionService实现和自定义的类型转换器 

<!-- ①注册ConversionService -->
<bean id="conversionService" class="org.springframework.format.support.FormattingConversionServiceFactoryBean">
	<property name="converters">
	   <list>
			<bean class="hb.base.convert.DateConverter">
				<constructor-arg value="yyyy-MM-dd"/>
			</bean>
		</list>
	</property>
	<!-- 格式化显示的配置
	<property name="formatters">
		<list>
			<bean class="hb.base.convert.DateFormatter">
				<constructor-arg value="yyyy-MM-dd"/>
			</bean>
		</list>
	</property>
-->
</bean>

（2、使用 ConfigurableWebBindingInitializer 注册conversionService

<!-- ②使用 ConfigurableWebBindingInitializer 注册conversionService -->
<bean id="webBindingInitializer"
	class="org.springframework.web.bind.support.ConfigurableWebBindingInitializer">
	<property name="conversionService" ref="conversionService" />
	<property name="validator" ref="validator" />
</bean>

（3、注册ConfigurableWebBindingInitializer 到RequestMappingHandlerAdapter

<!--Spring3.1开始的注解 HandlerAdapter -->
<bean
	class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
	<!--线程安全的访问session -->
	<property name="synchronizeOnSession" value="true" />
	<property name="webBindingInitializer" ref="webBindingInitializer"/>
</bean>

此时可能有人会问，如果我同时使用 PropertyEditor 和 ConversionService，执行顺序是什么呢？内部首先查找PropertyEditor 进行类型转换，如果没有找到相应的 PropertyEditor 再通过 ConversionService进行转换。