不同版本的springmvc可能有不同的处理方法，或者版本越高，处理方法越优化
实验的几种方式
public class User {
private int id;
private String username;
private String password;
private Date birth;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public Date getBirth() {
return birth;
}
public void setBirth(Date birth) {
this.birth = birth;
}
@Override
public String toString() {
return "User [id=" + id + ", username=" + username + ", password=" + password + ", birth=" + birth + "]";
}
}
应用场景1：
@Controller
public class UserController {
/**
* 登陆
* @param request
* @param response
* @return
*/
@RequestMapping(value = "/login.do", method = RequestMethod.POST)
public ModelAndView login(HttpServletRequest request, HttpServletResponse response, User user){
}
}
应用场景2:
public class UserController extends MultiActionController{
/**
* 登陆
* @param request
* @param response
* @return
*/
public ModelAndView login(HttpServletRequest request, HttpServletResponse response, User user){
}
}
}
1. @InitBinder--initBinder
spring 3.2.2（与标题无关）
UserController extends MultiActionController
@InitBinder
public void initBinder(WebDataBinder binder) {
System.out.println("@InitBinder-initBinder");
DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
CustomDateEditor dateEditor = new CustomDateEditor(df, true);
binder.registerCustomEditor(Date.class, dateEditor);
}
springmvc配置:
<context:component-scan base-package="com.byron.controller" /> <mvc:annotation-driven />
如果没有配置<mvc:annotation-driven />，@InitBinder将不起作用。此时对于继不继承MultiActionController已经没有意义，请求地址是通过注解的方式注册的
为什么@InitBinder需配合<mvc:annotation-driven />才起作用？
2.@Override--initBinder
UserController extends MultiActionController
@Override
protected void initBinder(HttpServletRequest request, ServletRequestDataBinder binder) throws Exception {
/*binder.setAutoGrowNestedPaths(true);
binder.setAutoGrowCollectionLimit(1024); */
DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
CustomDateEditor dateEditor = new CustomDateEditor(df, true);
binder.registerCustomEditor(Date.class, dateEditor);
System.out.println("hi, i am initBinder");
}
springmvc配置:
<bean id="urlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
<property name="mappings">
<props>
<prop key="/login.do">loginAction</prop>
</props>
</property>
</bean>
<bean id="loginAction" class="com.byron.controller.UserController">
<property name="methodNameResolver">
<ref local="methodNameResolver"/>
</property>
</bean>
<bean id="methodNameResolver" class="org.springframework.web.servlet.mvc.multiaction.ParameterMethodNameResolver">
<property name="paramName"><value>method</value></property>
<property name="defaultMethodName"><value>execute</value></property>
</bean>
此时,springmvc的映射器配置为SimpleUrlHandlerMapping,并且继承MultiActionController,覆盖父类中initBinder的定义,如：
protected void initBinder(HttpServletRequest request, ServletRequestDataBinder binder) throws Exception {
if (this.webBindingInitializer != null) {
this.webBindingInitializer.initBinder(binder, new ServletWebRequest(request));
}
}
3.自定义webBindingInitializer
这个与第二个有异曲同工之处,只不过方式不一样,相比于第二种的继承，这种方式更符合spring的开闭原则
<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
<property name="cacheSeconds" value="0"/>
<property name="webBindingInitializer">
<bean class="com.byron.controller.util.MyWebBindingInitializer"/>
</property>
</bean>
<context:component-scan base-package="com.byron.controller" />
<mvc:annotation-driven />
或
<bean id="urlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
<property name="mappings">
<props>
<prop key="/login.do">loginAction</prop>
</props>
</property>
</bean>
<bean id="loginAction" class="com.byron.controller.UserController">
<property name="methodNameResolver">
<ref local="methodNameResolver"/>
</property>
</bean>
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
<property name="cacheSeconds" value="0"/>
<property name="webBindingInitializer">
<bean class="com.byron.controller.util.MyWebBindingInitializer"/>
</property>
</bean>
还留下其它的一些扩展点如;
validators
对于以上1,3种方式，handlerMapping是通过注解配置，而第二种方式是通过xml配置实现映射器
4.在model中设置注解@DateTimeFormat(pattern = "yyyy-MM-dd")
spring配置
<context:component-scan base-package="com.byron.controller" />
<mvc:annotation-driven />
<mvc:annotation-driven />会注册DefaultAnnotationHandlerMapping和AnnotationMethodHandlerAdapter，由这2个类来处理@DateTimeFormat。
相当于:
<mvc:annotation-driven conversion-service="conversionService"/> <bean id="conversionService" class="org.springframework.format.support.FormattingConversionServiceFactoryBean"> <property name="converters"> <list> <!-- <bean class="com.*.StringToBeanConverter" /> --> </list> </property> </bean>
上述各种转换方法中，其实有时是相通的，一开始都是用xml去配置,只不过后来优化，直接使用注解配置的方式,代替了纯xml中配置各种bean的过程。
这种简化也是spring迭代升级中的一种趋势,用注解代替xml。但是对于开发者来说，一定程度上，也屏蔽的底端的实现和原理
附:源码分析
MultiActionController#bind
protected void bind(HttpServletRequest request, Object command) throws Exception {
logger.debug("Binding request parameters onto MultiActionController command");
ServletRequestDataBinder binder = createBinder(request, command);
binder.bind(request);
if (this.validators != null) {
for (Validator validator : this.validators) {
if (validator.supports(command.getClass())) {
ValidationUtils.invokeValidator(validator, command, binder.getBindingResult());
}
}
}
binder.closeNoCatch();
}
1.
binder.bind(request); 跟踪进去，调用PropertyEditor,conversionService中类型转换
2.
绑定数据结束后，调用校验validators
BeanWrapperImpl#convertIfNecessary
private Object convertIfNecessary(String propertyName, Object oldValue, Object newValue, Class<?> requiredType,
TypeDescriptor td) throws TypeMismatchException {
try {
return this.typeConverterDelegate.convertIfNecessary(propertyName, oldValue, newValue, requiredType, td);
}
catch (ConverterNotFoundException ex) {
PropertyChangeEvent pce =
new PropertyChangeEvent(this.rootObject, this.nestedPath + propertyName, oldValue, newValue);
throw new ConversionNotSupportedException(pce, td.getType(), ex);
}
catch (ConversionException ex) {
PropertyChangeEvent pce =
new PropertyChangeEvent(this.rootObject, this.nestedPath + propertyName, oldValue, newValue);
throw new TypeMismatchException(pce, requiredType, ex);
}
catch (IllegalStateException ex) {
PropertyChangeEvent pce =
new PropertyChangeEvent(this.rootObject, this.nestedPath + propertyName, oldValue, newValue);
throw new ConversionNotSupportedException(pce, requiredType, ex);
}
catch (IllegalArgumentException ex) {
PropertyChangeEvent pce =
new PropertyChangeEvent(this.rootObject, this.nestedPath + propertyName, oldValue, newValue);
throw new TypeMismatchException(pce, requiredType, ex);
}
}
this.typeConverterDelegate.convertIfNecessary(propertyName, oldValue, newValue, requiredType, td);
TypeConverterDelegate#convertIfNecessary
public <T> T convertIfNecessary(String propertyName, Object oldValue, Object newValue,
Class<T> requiredType, TypeDescriptor typeDescriptor) throws IllegalArgumentException {
Object convertedValue = newValue;
// Custom editor for this type?
PropertyEditor editor = this.propertyEditorRegistry.findCustomEditor(requiredType, propertyName);
ConversionFailedException firstAttemptEx = null;
// No custom editor but custom ConversionService specified?
ConversionService conversionService = this.propertyEditorRegistry.getConversionService();
if (editor == null && conversionService != null && convertedValue != null && typeDescriptor != null) {
TypeDescriptor sourceTypeDesc = TypeDescriptor.forObject(newValue);
TypeDescriptor targetTypeDesc = typeDescriptor;
if (conversionService.canConvert(sourceTypeDesc, targetTypeDesc)) {
try {
return (T) conversionService.convert(convertedValue, sourceTypeDesc, targetTypeDesc);
}
catch (ConversionFailedException ex) {
// fallback to default conversion logic below
firstAttemptEx = ex;
}
}
}
// Value not of required type?
if (editor != null || (requiredType != null && !ClassUtils.isAssignableValue(requiredType, convertedValue))) {
if (requiredType != null && Collection.class.isAssignableFrom(requiredType) && convertedValue instanceof String) {
TypeDescriptor elementType = typeDescriptor.getElementTypeDescriptor();
if (elementType != null && Enum.class.isAssignableFrom(elementType.getType())) {
convertedValue = StringUtils.commaDelimitedListToStringArray((String) convertedValue);
}
}
if (editor == null) {
editor = findDefaultEditor(requiredType);
}
convertedValue = doConvertValue(oldValue, convertedValue, requiredType, editor);
}
}
PropertyEditor editor = this.propertyEditorRegistry.findCustomEditor(requiredType, propertyName);
ConversionService conversionService = this.propertyEditorRegistry.getConversionService();
首先判断editor是否为空,不为空就用editor进行类型转换，否则如果conversionService不为空,则使用conversionService进行类型转换
TypeConverterDelegate的构造时，传入BeanWrapperImpl实例，即propertyEditorRegistry
参考：
Validation, Data Binding, and Type Conversion
https://docs.spring.io/spring/docs/current/spring-framework-reference/html/validation.html
解决java - spring mvc one init binder for all controllers
http://www.itkeyword.com/doc/5230440400468034x402/spring-mvc-one-init-binder-for-all-controllers
https://stackoverflow.com/questions/12486512/spring-mvc-initbinder-is-not-called-when-processing-ajax-request