Spring MVC 学习笔记 十五 what's new in spring mvc 3.1
1:mvc annotation-driven 新增标签
以下为spring mvc 3.1中annotation-driven所支持的全部配置。
- <mvc:annotation-driven message-codes-resolver ="bean ref" validator="" conversion-service="">
- <mvc:return-value-handlers>
- <bean></bean>
- </mvc:return-value-handlers>
- <mvc:argument-resolvers>
- </mvc:argument-resolvers>
- <mvc:message-converters>
- </mvc:message-converters>[/color]
- </mvc:annotation-driven>
<mvc:annotation-driven message-codes-resolver ="bean ref" validator="" conversion-service="">
<mvc:return-value-handlers>
<bean></bean>
</mvc:return-value-handlers>
<mvc:argument-resolvers>
</mvc:argument-resolvers>
<mvc:message-converters>
</mvc:message-converters>[/color]
</mvc:annotation-driven>
其中3.1新增部分如下
return-value-handlers
允许注册实现了HandlerMethodReturnValueHandler接口的bean，来对handler method的特定的返回类型做处理。
HandlerMethodReturnValueHandler接口中定义了两个方法
supportsReturnType 方法用来确定此实现类是否支持对应返回类型。
handleReturnValue 则用来处理具体的返回类型。
例如以下的handlerMethod
- @RequestMapping("/testReturnHandlers")
- public User testHandlerReturnMethod(){
- User u = new User();
- u.setUserName("test");
- return u;
- }
@RequestMapping("/testReturnHandlers")
public User testHandlerReturnMethod(){
User u = new User();
u.setUserName("test");
return u;
}
所返回的类型为一个pojo，正常情况下spring mvc无法解析，将转由DefaultRequestToViewNameTranslator 解析出一个缺省的view name，转到 testReturnHandlers.jsp，
我们增加以下配置
- <mvc:annotation-driven validator="validator">
- color=red] <mvc:return-value-handlers>
- <bean class="net.zhepu.web.handlers.returnHandler.UserHandlers"></bean>
- </mvc:return-value-handlers>[/color]
- </mvc:annotation-driven>
<mvc:annotation-driven validator="validator">
[color=red] <mvc:return-value-handlers>
<bean class="net.zhepu.web.handlers.returnHandler.UserHandlers"></bean>
</mvc:return-value-handlers>[/color]
</mvc:annotation-driven>
及如下实现类
- public class UserHandlers implements HandlerMethodReturnValueHandler {
- Logger logger = LoggerFactory.getLogger(this.getClass());
- @Override
- public boolean supportsReturnType(MethodParameter returnType) {
- Class<?> type = returnType.getParameterType();
- if(User.class.equals(type))
- {
- return true;
- }
- return false;
- }
- @Override
- public void handleReturnValue(Object returnValue,
- MethodParameter returnType, ModelAndViewContainer mavContainer,
- NativeWebRequest webRequest) throws Exception {
- logger.info("handler for return type users ");
- mavContainer.setViewName("helloworld");
- }
- }
public class UserHandlers implements HandlerMethodReturnValueHandler {
Logger logger = LoggerFactory.getLogger(this.getClass());
@Override
public boolean supportsReturnType(MethodParameter returnType) {
Class<?> type = returnType.getParameterType();
if(User.class.equals(type))
{
return true;
}
return false;
}
@Override
public void handleReturnValue(Object returnValue,
MethodParameter returnType, ModelAndViewContainer mavContainer,
NativeWebRequest webRequest) throws Exception {
logger.info("handler for return type users ");
mavContainer.setViewName("helloworld");
}
}
此时再访问 http://localhost:8080/springmvc/testReturnHandlers ，将交由 UserHandlers来处理返回类型为User的返回值。
argument-resolvers
允许注册实现了WebArgumentResolver接口的bean，来对handlerMethod中的用户自定义的参数或annotation进行解析
例如
- <mvc:annotation-driven validator="validator">
- <mvc:argument-resolvers>
- <bean
- class="net.zhepu.web.handlers.argumentHandler.MyCustomerWebArgumentHandler" />
- </mvc:argument-resolvers>
- </mvc:annotation-driven>
<mvc:annotation-driven validator="validator"> <mvc:argument-resolvers> <bean class="net.zhepu.web.handlers.argumentHandler.MyCustomerWebArgumentHandler" /> </mvc:argument-resolvers> </mvc:annotation-driven>
对应java代码如下
- public class MyCustomerWebArgumentHandler implements WebArgumentResolver {
- @Override
- public Object resolveArgument(MethodParameter methodParameter,
- NativeWebRequest webRequest) throws Exception {
- if (methodParameter.getParameterType().equals(MyArgument.class)) {
- MyArgument argu = new MyArgument();
- argu.setArgumentName("winzip");
- argu.setArgumentValue("123456");
- return argu;
- }
- return UNRESOLVED;
- }
- }
public class MyCustomerWebArgumentHandler implements WebArgumentResolver {
@Override
public Object resolveArgument(MethodParameter methodParameter,
NativeWebRequest webRequest) throws Exception {
if (methodParameter.getParameterType().equals(MyArgument.class)) {
MyArgument argu = new MyArgument();
argu.setArgumentName("winzip");
argu.setArgumentValue("123456");
return argu;
}
return UNRESOLVED;
}
}
这里我们定义了一个 customer webArgumentHandler，当handler method中参数类型为 MyArgument时生成对参数的类型绑定操作。
注意新注册的webArgumentHandler的优先级最低，即如果系统缺省注册的ArgumentHandler已经可以解析对应的参数类型时，就不会再调用到新注册的customer ArgumentHandler了。
message-converters
允许注册实现了HttpMessageConverter接口的bean，来对requestbody 或responsebody中的数据进行解析
例如
假设我们使用 text/plain格式发送一串字符串来表示User对象，各个属性值使用”|”来分隔。例如 winzip|123456|13818888888，期望转为user对象，各属性内容为user.username = winzip,user.password=123456;user.mobileNO = 13818888888
以下代码中supports表示此httpmessageConverter实现类针对 User类进行解析。
构造函数中调用 super(new MediaType("text", "plain"));以表示支持 text/plain格式的输入。
- public class MyCustomerMessageConverter extends
- AbstractHttpMessageConverter<Object> {
- @Override
- protected boolean supports(Class<?> clazz) {
- if (clazz.equals(User.class)) {
- return true;
- }
- return false;
- }
- public MyCustomerMessageConverter() {
- super(new MediaType("text", "plain"));
- }
- @Override
- protected Object readInternal(Class<? extends Object> clazz,
- HttpInputMessage inputMessage) throws IOException,
- HttpMessageNotReadableException {
- Charset charset;
- MediaType contentType = inputMessage.getHeaders().getContentType();
- if (contentType != null && contentType.getCharSet() != null) {
- charset = contentType.getCharSet();
- } else {
- charset = Charset.forName("UTF-8");
- }
- String input = FileCopyUtils.copyToString(new InputStreamReader(
- inputMessage.getBody(), charset));
- logger.info(input);
- String[] s = input.split("\\|");
- User u = new User();
- u.setUserName(s[0]);
- u.setPassword(s[1]);
- u.setMobileNO(s[2]);
- return u;
- }
- @Override
- protected void writeInternal(Object t, HttpOutputMessage outputMessage)
- throws IOException, HttpMessageNotWritableException {
- }
public class MyCustomerMessageConverter extends
AbstractHttpMessageConverter<Object> {
@Override
protected boolean supports(Class<?> clazz) {
if (clazz.equals(User.class)) {
return true;
}
return false;
}
public MyCustomerMessageConverter() {
super(new MediaType("text", "plain"));
}
@Override
protected Object readInternal(Class<? extends Object> clazz,
HttpInputMessage inputMessage) throws IOException,
HttpMessageNotReadableException {
Charset charset;
MediaType contentType = inputMessage.getHeaders().getContentType();
if (contentType != null && contentType.getCharSet() != null) {
charset = contentType.getCharSet();
} else {
charset = Charset.forName("UTF-8");
}
String input = FileCopyUtils.copyToString(new InputStreamReader(
inputMessage.getBody(), charset));
logger.info(input);
String[] s = input.split("\\|");
User u = new User();
u.setUserName(s[0]);
u.setPassword(s[1]);
u.setMobileNO(s[2]);
return u;
}
@Override
protected void writeInternal(Object t, HttpOutputMessage outputMessage)
throws IOException, HttpMessageNotWritableException {
}
修改servlet context xml配置文件，增加message-converters的相应配置如下。
- <mvc:message-converters>
- <bean class="net.zhepu.web.handlers.messageConverterHandler.MyCustomerMessageConverter"></bean>
- </mvc:message-converters>
<mvc:message-converters>
<bean class="net.zhepu.web.handlers.messageConverterHandler.MyCustomerMessageConverter"></bean>
</mvc:message-converters>
message-codes-resolver
先看看spring mvc中对于messageCodeResolver的用法。
spring mvc中使用DefaultMessageCodesResolver作为缺省的MessageCodesResolver的实现类，其作用是对valid errors中的errorcode进行解析。其解析方式如下
当解析error global object注册的errorcode时，errorcode的查找顺序为
1：errorcode.validationobjectname
2：errorcode
例如
以下声明中
- public String helloWorld2(@ModelAttribute("user") User u,
- BindingResult result)
public String helloWorld2(@ModelAttribute("user") User u,
BindingResult result)
当使用 result.reject("testFlag");来注册一个globat error object时，spring mvc将在messageSource中先查找 testFlag.user这个errorcode,当找不到时再查找testFlag这个errorcode。
当解析fields error时，将按以下顺序生成error code
1.: code + "." + object name + "." + field
2.: code + "." + field
3.: code + "." + field type
4.: code
还是以上面的代码为例，当使用 result.rejectValue("userName", "testFlag");来注册一个针对user.UserName属性的错误描述时，errors对象中将生成以下的error code list,
1.: testFlag.user.userName
2.: testFlag.userName
3.: testFlag.java.lang.String
4.: testFlag
而mvc:annotation-driven新增的属性message-codes-resolver则提供了注册自定义的MessageCodesResolver的手段。
例如上面想要在所有的error code前增加前缀validation.的话，可以这么来做
- <mvc:annotation-driven validator="validator" message-codes-resolver="messageCodeResolver">
- </mvc:annotation-driven>
<mvc:annotation-driven validator="validator" message-codes-resolver="messageCodeResolver"> </mvc:annotation-driven>
新增messageCodeResolver bean定义如下
- <bean id="messageCodeResolver" class="org.springframework.validation.DefaultMessageCodesResolver">
- <property name="prefix" value="validation."></property>
- </bean>
<bean id="messageCodeResolver" class="org.springframework.validation.DefaultMessageCodesResolver"> <property name="prefix" value="validation."></property> </bean>
此时，所有的errorcode都会生成缺省前缀 validation.
例如前面的 result.reject("testFlag"); 生成的error code list就变为了
validation.testFlag.user 和 validation.testFlag了。
2: @RequestMapping 新增参数Consumes 和Produces
前面介绍过@RequestMapping的参数中有一个header的参数，来指定handler method能接受的http request 请求的header内容。
而consumes和produces则更进一步，直接指定所能接受或产生的request请求的content type。
例如
- @RequestMapping(value="/testMsgConverter",consumes="text/plain",produces="application/json")
@RequestMapping(value="/testMsgConverter",consumes="text/plain",produces="application/json")
表示handlermethod接受的请求的header中的 Content-Type为text/plain;
Accept为application/json
3: URI Template 新增功能
这部分的例子直接照抄Spring 3.1 M2: Spring MVC Enhancements中的示例
1: @PathVariable 声明的参数可自动加入到model中。
例如
- @RequestMapping("/develop/apps/edit/{slug}")
- public String editForm(@PathVariable String slug, Model model) {
- model.addAttribute("slug", slug);
- // ...
- }
@RequestMapping("/develop/apps/edit/{slug}")
public String editForm(@PathVariable String slug, Model model) {
model.addAttribute("slug", slug);
// ...
}
现在可以写为
- @RequestMapping("/develop/apps/edit/{slug}")
- public String editForm(@PathVariable String slug, Model model) {
- // model contains "slug" variable
- }
@RequestMapping("/develop/apps/edit/{slug}")
public String editForm(@PathVariable String slug, Model model) {
// model contains "slug" variable
}
2：handler method中的redirect string可支持url template了
例如
- @RequestMapping(
- value="/groups/{group}/events/{year}/{month}/{slug}/rooms",
- method=RequestMethod.POST)
- public String createRoom(
- @PathVariable String group, @PathVariable Integer year,
- @PathVariable Integer month, @PathVariable String slug) {
- // ...
- return "redirect:/groups/" + group + "/events/" + year + "/" + month + "/" + slug;
- }
@RequestMapping(
value="/groups/{group}/events/{year}/{month}/{slug}/rooms",
method=RequestMethod.POST)
public String createRoom(
@PathVariable String group, @PathVariable Integer year,
@PathVariable Integer month, @PathVariable String slug) {
// ...
return "redirect:/groups/" + group + "/events/" + year + "/" + month + "/" + slug;
}
现在可写为
- @RequestMapping(
- value="/groups/{group}/events/{year}/{month}/{slug}/rooms",
- method=RequestMethod.POST)
- public String createRoom(
- @PathVariable String group, @PathVariable Integer year,
- @PathVariable Integer month, @PathVariable String slug) {
- // ...
- return "redirect:/groups/{group}/events/{year}/{month}/{slug}";
- }
@RequestMapping(
value="/groups/{group}/events/{year}/{month}/{slug}/rooms",
method=RequestMethod.POST)
public String createRoom(
@PathVariable String group, @PathVariable Integer year,
@PathVariable Integer month, @PathVariable String slug) {
// ...
return "redirect:/groups/{group}/events/{year}/{month}/{slug}";
}
3：url template中可支持databinding 了
例如
- @RequestMapping("/people/{firstName}/{lastName}/SSN")
- public String find(Person person,
- @PathVariable String firstName,
- @PathVariable String lastName) {
- person.setFirstName(firstName);
- person.setLastName(lastName);
- // ...
- }
@RequestMapping("/people/{firstName}/{lastName}/SSN")
public String find(Person person,
@PathVariable String firstName,
@PathVariable String lastName) {
person.setFirstName(firstName);
person.setLastName(lastName);
// ...
}
现在可以写成
- @RequestMapping("/people/{firstName}/{lastName}/SSN")
- public String search(Person person) {
- // person.getFirstName() and person.getLastName() are populated
- // ...
- }
@RequestMapping("/people/{firstName}/{lastName}/SSN")
public String search(Person person) {
// person.getFirstName() and person.getLastName() are populated
// ...
}
4: Validation For @RequestBody
@RequestBody现在直接支持@valid标注了,如果validation失败，将抛出
RequestBodyNotValidException。
具体处理逻辑可见 spring 中的RequestResponseBodyMethodProcessor中的以下代码。
- public Object resolveArgument(MethodParameter parameter,
- ModelAndViewContainer mavContainer,
- NativeWebRequest webRequest,
- WebDataBinderFactory binderFactory) throws Exception {
- Object arg = readWithMessageConverters(webRequest, parameter, parameter.getParameterType());
- if (shouldValidate(parameter, arg)) {
- String argName = Conventions.getVariableNameForParameter(parameter);
- WebDataBinder binder = binderFactory.createBinder(webRequest, arg, argName);
- binder.validate();
- Errors errors = binder.getBindingResult();
- if (errors.hasErrors()) {
- throw new RequestBodyNotValidException(errors);
- }
- }
- return arg;
- }
public Object resolveArgument(MethodParameter parameter,
ModelAndViewContainer mavContainer,
NativeWebRequest webRequest,
WebDataBinderFactory binderFactory) throws Exception {
Object arg = readWithMessageConverters(webRequest, parameter, parameter.getParameterType());
if (shouldValidate(parameter, arg)) {
String argName = Conventions.getVariableNameForParameter(parameter);
WebDataBinder binder = binderFactory.createBinder(webRequest, arg, argName);
binder.validate();
Errors errors = binder.getBindingResult();
if (errors.hasErrors()) {
throw new RequestBodyNotValidException(errors);
}
}
return arg;
}
5:annotation-driven缺省注册类的改变
Spring 3.0.x中使用了annotation-driven后，缺省使用DefaultAnnotationHandlerMapping 来注册handler method和request的mapping关系。
AnnotationMethodHandlerAdapter来在实际调用handlermethod前对其参数进行处理。
并在dispatcherServlet中，当用户未注册自定义的ExceptionResolver时，注册AnnotationMethodHandlerExceptionResolver来对使用@ExceptionHandler标注的异常处理函数进行解析处理(这也导致当用户注册了自定义的exeptionResolver时将可能导致无法处理@ExceptionHandler)。
在spring mvc 3.1中，对应变更为
DefaultAnnotationHandlerMapping -> RequestMappingHandlerMapping
AnnotationMethodHandlerAdapter -> RequestMappingHandlerAdapter
AnnotationMethodHandlerExceptionResolver -> ExceptionHandlerExceptionResolver
以上都在使用了annotation-driven后自动注册。
而且对应分别提供了AbstractHandlerMethodMapping , AbstractHandlerMethodAdapter和 AbstractHandlerMethodExceptionResolver以便于让用户更方便的实现自定义的实现类。