Spring MVC Controller传递枚举值的实例

Spring MVC Controller传递枚举值

功能描述

本文将通过一个小示例，展示在请求参数中传递枚举值。

枚举定义

角色类定义：

				?

									public enum RoleEnum {

									 EMPLOYEE((short)1, "Employee"), MANAGER((short)2, "Manager");

									 private Short value;

									 private String desc;

									 private RoleEnum(Short value, String desc) {

									  this.value = value;

									  this.desc = desc;

									 }

									 public Short value() {

									  return value;

									 }

									 public String desc() {

									  return desc;

									 }

									}

定义Controller类

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									@RestController

									@Slf4j

									public class HomeController {

									 @GetMapping("/home")

									 public String getDemo(@RequestParam("role") RoleEnum role) {

									  log.info("Role Enum:{}" + role);  

									  return role.desc();

									 }

									}

说明：在这里RoleEnum之内作为@RequestParam参数。

请求示例

Case1: http://localhost:8080/home?role=EMPLOYEE

结论：正确返回， Employee

Case2: http://localhost:8080/home?role=Employee

报错，具体信息如下：

				?

									Whitelabel Error Page

									This application has no explicit mapping for /error, so you are seeing this as a fallback.

									Thu May 14 11:21:32 CST 2020

									There was an unexpected error (type=Bad Request, status=400).

									Failed to convert value of type 'java.lang.String' to required type 'org.course.data.domain.RoleEnum'; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [@org.springframework.web.bind.annotation.RequestParam org.course.data.domain.RoleEnum] for value 'employee'; nested exception is java.lang.IllegalArgumentException: No enum constant org.course.data.domain.RoleEnum.employee

									org.springframework.web.method.annotation.MethodArgumentTypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'org.course.data.domain.RoleEnum'; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [@org.springframework.web.bind.annotation.RequestParam org.course.data.domain.RoleEnum] for value 'employee'; nested exception is java.lang.IllegalArgumentException: No enum constant org.course.data.domain.RoleEnum.employee

									   at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:133)

									   at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:127)

									   at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:167)

									   at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:134)

									   at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105)

									   at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:893)

									   at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:798)

									   at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)

									   at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)

									   at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)

									   at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)

									   at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)

									   at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)

									   at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)

									   at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)

									   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)

									   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

									   at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)

									   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

									   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

									   at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)

									   at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)

									   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

									   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

									   at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)

									   at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)

									   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

									   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

									   at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:94)

									   at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)

									   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

									   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

									   at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)

									   at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)

									   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

									   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

									   at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)

									   at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)

									   at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)

									   at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)

									   at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)

									   at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)

									   at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)

									   at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367)

									   at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)

									   at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)

									   at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1639)

									   at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)

									   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)

									   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)

									   at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)

									   at java.lang.Thread.run(Thread.java:748)

									Caused by: org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [@org.springframework.web.bind.annotation.RequestParam org.course.data.domain.RoleEnum] for value 'employee'; nested exception is java.lang.IllegalArgumentException: No enum constant org.course.data.domain.RoleEnum.employee

									   at org.springframework.core.convert.support.ConversionUtils.invokeConverter(ConversionUtils.java:47)

									   at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:191)

									   at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:129)

									   at org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:73)

									   at org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:53)

									   at org.springframework.validation.DataBinder.convertIfNecessary(DataBinder.java:693)

									   at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:125)

									   ... 51 more

									Caused by: java.lang.IllegalArgumentException: No enum constant org.course.data.domain.RoleEnum.employee

									   at java.lang.Enum.valueOf(Enum.java:238)

									   at org.springframework.core.convert.support.StringToEnumConverterFactory$StringToEnum.convert(StringToEnumConverterFactory.java:52)

									   at org.springframework.core.convert.support.StringToEnumConverterFactory$StringToEnum.convert(StringToEnumConverterFactory.java:38)

									   at org.springframework.core.convert.support.GenericConversionService$ConverterFactoryAdapter.convert(GenericConversionService.java:436)

									   at org.springframework.core.convert.support.ConversionUtils.invokeConverter(ConversionUtils.java:41)

									   ... 57 more

实现分析：

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									final class StringToEnumConverterFactory implements ConverterFactory<String, Enum> {

									    StringToEnumConverterFactory() {

									    }

									    public <T extends Enum> Converter<String, T> getConverter(Class<T> targetType) {

									        return new StringToEnumConverterFactory.StringToEnum(ConversionUtils.getEnumType(targetType));

									    }

									    private class StringToEnum<T extends Enum> implements Converter<String, T> {

									        private final Class<T> enumType;

									        public StringToEnum(Class<T> enumType) {

									            this.enumType = enumType;

									        }

									        public T convert(String source) {

									            return source.isEmpty() ? null : Enum.valueOf(this.enumType, source.trim());

									        }

									    }

									}

底层实现为将String转换为Enum值的过程。

结论

基于枚举可以限定具体值，简单易用。但是缺点是在扩展enum之时，无法做法平滑过度升级，会吹安短暂的异常情况。

Spring MVC 枚举传值问题

今天遇到算是棘手的一个枚举的问题，后台Controller参数是一个对象，而对象里面有个枚举类型的属性，死活不能传值。

最后找到解决方案

实体对象：

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									@Entity

									@Table(name="xx_sn")

									@SequenceGenerator(name = "sequenceGenerator", sequenceName = "xx_sn_sequence")

									public class ShoppTest extends BaseEntity{

									    private static final long serialVersionUID = 2756395514949325790L;

									    /**

									     * 枚举

									     * @author Administrator

									     *

									     */

									    public enum Type{

									        /** 商品 */

									        product,

									        /** 订单 */

									        order,

									        /** 收款单 */

									        payment,

									        /** 退款单 */

									        refunds,

									        /** 发货单 */

									        shipping,

									        /** 退货单 */

									        returns

									    }

									    @Column(nullable = false, updatable = false, unique = true)

									    private Type type;

									    @Column(nullable = false)

									    private String lastValue;

									    public String getLastValue() {

									        return lastValue;

									    }

									    public void setLastValue(String lastValue) {

									        this.lastValue = lastValue;

									    }

									    public Type getType() {

									        return type;

									    }

									    public void setType(Type type) {

									        this.type = type;

									    }

Controller代码：

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									@RequestMapping("/save")

									public String save(ShoppTest st,String tp){

									 st.setType(Enum.valueOf(Type.class, tp));

									 shoppTestServiceImpl.save(st);

									 return "redirect:list.jhtml";

									}

前台代码：

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									<form id="inputForm" action="save.jhtml" method="post">

									<table class="input">

									<tr>

									<th>

									${message("test.lastValue")}:

									</th>

									<td colspan="2">

									<input type="text" name="lastValue" class="text">

									</td>

									</tr>

									<tr>

									<th>

									<span class="requiredField">*</span>${message("test.type")}:

									</th>

									<td colspan="2">

									<input type="text" name="tp" class="text" maxlength="200" />

									</td>

									</tr>

									</table>

									<table class="input">

									<tr>

									<th> 

									</th>

									<td>

									<input type="submit" class="button" value="${message("admin.common.submit")}" />

									<input type="button" class="button" value="${message("admin.common.back")}" οnclick="location.href='list.jhtml'" />

									</td>

									</tr>

									</table>

									</form>