Java 如何使用Spring Boot实现REST服务

我想用IntelliJ IDE构建一个带有“Spring Boot”的简单微服务

这个微服务的一个方法应该是在输入中接受一个列表和一个双精度值

所以我在构建这个代码：

import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

@RestController
public class ECGController {

    private double v1 = 0.01;
    private double v2 = 0.01;
    private int il = 0;
    private static final double step = 0.0025;

    @PostMapping("/clearF3A")
    public List<Double> clearF3A(ArrayList<Integer> RRin, Double CR){
        try{

        }catch(Exception e){

        }
    }

但如果我尝试执行此请求，我可以显示以下消息错误：

java.lang.NullPointerException
    at com.eresult.cleanECG.com.cleanECG.controller.ECGController.clearF3A(ECGController.java:36)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:661)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
    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:52)
    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:99)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    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.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:108)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    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:81)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    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:197)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    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:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
    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)
java.lang.NullPointerException

你的要求不好

与提供

ArrayList RRin，Double CR

to

clearF3A

函数不同，您应该有一个表示整个post主体（整个JSON文档）的对象。这是规则。在本例中，传递的对象应该有两个参数，一个是

rrin

array，第二个应该是

cr

。此外，该参数应使用

@RequestBody

大致上，这就是您需要的：

@PostMapping("/clearF3A")
public List<Double> clearF3A(@RequestBody ClearF3ARequest){
    ...
}

class ClearF3ARequest {
    private ArrayList<Integer> RRin;
    private Double CR;
}

@PostMapping（/clearF3A）
公共列表clearF3A（@RequestBody ClearF3ARequest）{
...
}
类ClearF3ARequest{
私人ArrayList RRin；
私人双CR；
}

---

希望这有帮助。

创建一个新对象来表示JSON结构。例如：

public class EcgInput {

  @JsonProperty("RRin")
  private List<Integer> rrIn;

  @JsonProperty("CR")
  private Double cr;

//todo: add the getters and setters and methods like toString()

}

公共类EcgInput{
@JsonProperty（“RRin”）
私人名单；
@JsonProperty（“CR”）
私人双cr；
//todo:添加getter和setter以及类似于toString（）的方法
}

公共类EcgOutput{
@JsonProperty（“输出”）
私有列表输出；
//todo:添加getter和setter以及类似于toString（）的方法
}

然后在控制器中，将方法更改为：

@PostMapping("/clearF3A")
public ResponseEntity<EcgOutput> clearF3A(@RequestBody EcgInput ecgInput) {
   //todo: your logic
   EcgOutput output = new EcgOutput();
   //todo: put your result inside it

   return new ResponseEntity<>(output, HttpStatus.OK);
}

@PostMapping（/clearF3A）
公共响应clearF3A（@RequestBody EcgInput EcgInput）{
//托多：你的逻辑
EcgOutput输出=新的EcgOutput（）；
//todo:把你的结果放进去
返回新的响应状态（输出，HttpStatus.OK）；
}

---

Jackson将把JSON翻译成这些对象，反之亦然。

第36行对应什么？您没有显示控制器方法中的代码，因此我们必须猜测错误所在…问题是这两个变量为空。您是否使用jackson-default json处理程序进行spring boot？我的第一个猜测是参数应该是单个对象，用一些

@RequestBody

注释。您正在发送JSON，因此必须使用Jackson将其转换为对象。

public class EcgOutput {

  @JsonProperty("output")
  private List<Double> output;

//todo: add the getters and setters and methods like toString()
}

@PostMapping("/clearF3A")
public ResponseEntity<EcgOutput> clearF3A(@RequestBody EcgInput ecgInput) {
   //todo: your logic
   EcgOutput output = new EcgOutput();
   //todo: put your result inside it

   return new ResponseEntity<>(output, HttpStatus.OK);
}