我正在使用 Spring Boot 。我有一个 rest api POST 调用，我需要使用 x-www-form-urlencoded 发送正文，调用不需要 header 。我可以从 postman 那里点击这个网址，然后在数据库中成功创建了一行。但是当我尝试从 Java 端调用它时，我收到了 400 错误请求异常。
下面是我在 Java 中尝试过的。
MultiValueMap<String, String> map = new LinkedMultiValueMap<String, String>();
map.add("param1", "123");
map.add("param2", "456");
map.add("param3", "789");
map.add("param4", "123");
map.add("param5", "456");
HttpHeaders headers = new HttpHeaders();
final HttpEntity<MultiValueMap<String, String>> entity = new HttpEntity<MultiValueMap<String, String>>(map,
headers);
try {
RestTemplate restTemplate = new RestTemplate();
String response = restTemplate.postForObject(
"https://url", entity,
String.class);
System.out.println(response);
} catch (final Exception e) {
throw new RuntimeException();
}
我遇到了这个异常。
org.springframework.web.client.HttpClientErrorException: 400 Bad Request
我也像下面这样尝试并得到了同样的异常。
ResponseEntity<String> x = restTemplate.exchange("https://url", HttpMethod.POST,
map, String.class);
这是完整的堆栈跟踪
org.springframework.web.client.HttpClientErrorException: 400 Bad Request
at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:91) ~[spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.web.client.RestTemplate.handleResponse(RestTemplate.java:641) ~[spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:597) ~[spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:557) ~[spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.web.client.RestTemplate.postForObject(RestTemplate.java:357) ~[spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at com.bbtransact.icp.api.paymentmethodscards.internal.UserPaymentmethodsCardsServiceAgent.savePaymentCreditCards(UserPaymentmethodsCardsServiceAgent.java:59) ~[bin/:na]
at com.bbtransact.icp.api.paymentmethodscards.resource.dao.CreditDebitCardsDAO.saveCreditDebitCard(CreditDebitCardsDAO.java:147) [bin/:na]
at com.bbtransact.icp.api.paymentmethodscards.resource.dao.CreditDebitCardsDAO$$FastClassBySpringCGLIB$$12a57300.invoke(<generated>) [bin/:na]
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) [spring-core-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:720) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:85) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at com.bbtransact.icp.api.paymentmethodscards.aspect.LogAspect.doAroundResourceHelper(LogAspect.java:72) [bin/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_60]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_60]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_60]
at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_60]
at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:621) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:610) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:68) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:655) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at com.bbtransact.icp.api.paymentmethodscards.resource.dao.CreditDebitCardsDAO$$EnhancerBySpringCGLIB$$3d31a5af.saveCreditDebitCard(<generated>) [bin/:na]
at com.bbtransact.icp.api.paymentmethodscards.services.impl.CreditDebitCardsServiceImpl.saveCreditDebitCard(CreditDebitCardsServiceImpl.java:70) [bin/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_60]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_60]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_60]
at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_60]
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:302) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:85) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at com.bbtransact.icp.api.paymentmethodscards.aspect.LogAspect.doAroundService(LogAspect.java:55) [bin/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_60]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_60]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_60]
at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_60]
at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:621) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:610) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:68) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:208) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at com.sun.proxy.$Proxy96.saveCreditDebitCard(Unknown Source) [na:na]
at com.bbtransact.icp.api.paymentmethodscards.controllers.CreditDebitCardsController.saveCreditDebitCard(CreditDebitCardsController.java:92) [bin/:na]
at com.bbtransact.icp.api.paymentmethodscards.controllers.CreditDebitCardsController$$FastClassBySpringCGLIB$$5232db9d.invoke(<generated>) [bin/:na]
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) [spring-core-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:720) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:85) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at com.bbtransact.icp.api.paymentmethodscards.aspect.LogAspect.doAroundController(LogAspect.java:37) [bin/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_60]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_60]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_60]
at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_60]
at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:621) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:610) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:68) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:655) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at com.bbtransact.icp.api.paymentmethodscards.controllers.CreditDebitCardsController$$EnhancerBySpringCGLIB$$96f8dfac.saveCreditDebitCard(<generated>) [bin/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_60]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_60]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_60]
at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_60]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:222) [spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137) [spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) [spring-webmvc-4.2.2.RELEASE.jar:4.2.2.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:806) [spring-webmvc-4.2.2.RELEASE.jar:4.2.2.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:729) [spring-webmvc-4.2.2.RELEASE.jar:4.2.2.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) [spring-webmvc-4.2.2.RELEASE.jar:4.2.2.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) [spring-webmvc-4.2.2.RELEASE.jar:4.2.2.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) [spring-webmvc-4.2.2.RELEASE.jar:4.2.2.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) [spring-webmvc-4.2.2.RELEASE.jar:4.2.2.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872) [spring-webmvc-4.2.2.RELEASE.jar:4.2.2.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:648) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) [spring-webmvc-4.2.2.RELEASE.jar:4.2.2.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-embed-websocket-8.0.30.jar:8.0.30]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.springframework.boot.actuate.autoconfigure.EndpointWebMvcAutoConfiguration$ApplicationContextHeaderFilter.doFilterInternal(EndpointWebMvcAutoConfiguration.java:237) [spring-boot-actuator-1.3.2.RELEASE.jar:1.3.2.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.springframework.cloud.sleuth.instrument.web.TraceFilter.doFilterInternal(TraceFilter.java:153) [spring-cloud-sleuth-core-1.0.0.M1.jar:1.0.0.M1]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:111) [spring-boot-actuator-1.3.2.RELEASE.jar:1.3.2.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:121) [spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.springframework.boot.actuate.autoconfigure.MetricsFilter.doFilterInternal(MetricsFilter.java:103) [spring-boot-actuator-1.3.2.RELEASE.jar:1.3.2.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:521) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1096) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:674) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500) [tomcat-embed-core-8.0.30.jar:8.0.30]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1456) [tomcat-embed-core-8.0.30.jar:8.0.30]
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [na:1.8.0_60]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [na:1.8.0_60]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.0.30.jar:8.0.30]
at java.lang.Thread.run(Unknown Source) [na:1.8.0_60]
我该如何解决这个问题？
最佳答案
这对我有用。问题是早些时候我在使用交换方法时没有设置内容类型(标题)。
MultiValueMap<String, String> map = new LinkedMultiValueMap<String, String>();
map.add("param1", "123");
map.add("param2", "456");
map.add("param3", "789");
map.add("param4", "123");
map.add("param5", "456");
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
final HttpEntity<MultiValueMap<String, String>> entity = new HttpEntity<MultiValueMap<String, String>>(map ,
headers);
JSONObject jsonObject = null;
try {
RestTemplate restTemplate = new RestTemplate();
ResponseEntity<String> responseEntity = restTemplate.exchange(
"https://url", HttpMethod.POST, entity,
String.class);
if (responseEntity.getStatusCode() == HttpStatus.CREATED) {
try {
jsonObject = new JSONObject(responseEntity.getBody());
} catch (JSONException e) {
throw new RuntimeException("JSONException occurred");
}
}
} catch (final HttpClientErrorException httpClientErrorException) {
throw new ExternalCallBadRequestException();
} catch (HttpServerErrorException httpServerErrorException) {
throw new ExternalCallServerErrorException(httpServerErrorException);
} catch (Exception exception) {
throw new ExternalCallServerErrorException(exception);
}
ExternalCallBadRequestException 和 ExternalCallServerErrorException 是这里的自定义异常。
注意:记住当收到 4xx 错误时会抛出 HttpClientErrorException。因此，如果您发送的请求错误设置 header 或发送错误数据，您可能会收到此异常。
关于java - org.springframework.web.client.HttpClientErrorException : 400 Bad Request，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/38019212/
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什么是ruby的rack或python的Java的wsgi？还有一个路由库。 最佳答案 来自Python标准PEP333:Bycontrast,althoughJavahasjustasmanywebapplicationframeworksavailable,Java's"servlet"APImakesitpossibleforapplicationswrittenwithanyJavawebapplicationframeworktoruninanywebserverthatsupportstheservletAPI.ht
这篇文章是继上一篇文章“Observability：从零开始创建Java微服务并监控它（一）”的续篇。在上一篇文章中，我们讲述了如何创建一个Javaweb应用，并使用Filebeat来收集应用所生成的日志。在今天的文章中，我来详述如何收集应用的指标，使用APM来监控应用并监督web服务的在线情况。源码可以在地址 https://github.com/liu-xiao-guo/java_observability 进行下载。摄入指标指标被视为可以随时更改的时间点值。当前请求的数量可以改变任何毫秒。你可能有1000个请求的峰值，然后一切都回到一个请求。这也意味着这些指标可能不准确，你还想提取最小/
HashMap中为什么引入红黑树，而不是AVL树呢1.概述开始学习这个知识点之前我们需要知道，在JDK1.8以及之前，针对HashMap有什么不同。JDK1.7的时候，HashMap的底层实现是数组+链表JDK1.8的时候，HashMap的底层实现是数组+链表+红黑树我们要思考一个问题，为什么要从链表转为红黑树呢。首先先让我们了解下链表有什么不好？？？2.链表上述的截图其实就是链表的结构，我们来看下链表的增删改查的时间复杂度增：因为链表不是线性结构，所以每次添加的时候，只需要移动一个节点，所以可以理解为复杂度是N(1)删：算法时间复杂度跟增保持一致查：既然是非线性结构，所以查询某一个节点的时候
遍历文件夹我们通常是使用递归进行操作，这种方式比较简单，也比较容易理解。本文为大家介绍另一种不使用递归的方式，由于没有使用递归，只用到了循环和集合，所以效率更高一些！一、使用递归遍历文件夹整体思路1、使用File封装初始目录，2、打印这个目录3、获取这个目录下所有的子文件和子目录的数组。4、遍历这个数组，取出每个File对象4-1、如果File是否是一个文件，打印4-2、否则就是一个目录，递归调用代码实现publicclassSearchFile{publicstaticvoidmain(String[]args){//初始目录Filedir=newFile("d:/Dev");Datebeg
我基本上来自Java背景并且努力理解Ruby中的模运算。(5%3)(-5%3)(5%-3)(-5%-3)Java中的上述操作产生，2个-22个-2但在Ruby中，相同的表达式会产生21个-1-2.Ruby在逻辑上有多擅长这个？模块操作在Ruby中是如何实现的？如果将同一个操作定义为一个web服务，两个服务如何匹配逻辑。 最佳答案 在Java中，模运算的结果与被除数的符号相同。在Ruby中，它与除数的符号相同。remainder()在Ruby中与被除数的符号相同。您可能还想引用modulooperation.
Java的Collections.unmodifiableList和Collections.unmodifiableMap在Ruby标准API中是否有等价物？ 最佳答案 使用freeze应用程序接口(interface):Preventsfurthermodificationstoobj.ARuntimeErrorwillberaisedifmodificationisattempted.Thereisnowaytounfreezeafrozenobject.SeealsoObject#frozen?.Thismethodretur