概述
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
@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：
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：
@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：
@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：
<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>
因为springMVC对于枚举这种特殊的数据类型不能直接进行数据注入，所以访问Controller的时候直接就是400错误。
所以我这里用String去接收前台传来的枚举需要的数据，也就是“tp”，用到Enum.ValueOf（）;
ValueOf需要两个参数，第一个参数类型就是自己定义的枚举类类型，第二个参数是你枚举里面
定义的字段名字，这个字段就对应了你枚举所得到的值。
最终取到值后赋值给对象里面的枚举。
以上为个人经验，希望能给大家一个参考，也希望大家多多支持靠谱客。
最后
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