title: Spring actuator/health results in HTTP 400 Bad request, JSON parse error
body: <p>i have an existing spring boot app. I just added actuator to the <code>pom.xml</code>
  <code>org.springframework.boot</code>, <code>spring-boot-starter-actuator</code>.</p>
  
  <p>actuator works
  <code>actuator/health results</code> in error with <code>400</code> response code</p>
  
  <p>from logs: it looks like spring failed to resolve some parameter.
  below is the log.</p>
  
  <blockquote>
    <p>019-05-15 14:38:24.747 DEBUG 8964 --- [nio-8090-exec-3]
    o.s.web.servlet.DispatcherServlet        : GET "/actuator/health",
    parameters={} 2019-05-15 14:38:24.748 DEBUG 8964 --- [nio-8090-exec-3]
    s.b.a.e.w.s.WebMvcEndpointHandlerMapping : Mapped to Actuator web
    endpoint 'health' 2019-05-15 14:38:24.754 DEBUG 8964 ---
    [nio-8090-exec-3] .w.s.m.m.a.ServletInvocableHandlerMethod : Could not
    resolve parameter [1] in public java.lang.Object
    org.springframework.boot.actuate.endpoint.web.servlet.AbstractWebMvcEndpointHandlerMapping$OperationHandler.handle(javax.servlet.http.HttpServletRequest,java.util.Map): JSON parse error: Unrecognized token 'eth': was
    expecting ('true', 'false' or 'null'); nested exception is
    com.fasterxml.jackson.core.JsonParseException: Unrecognized token
    'eth': was expecting ('true', 'false' or 'null')  at [Source:
    (PushbackInputStream); line: 1, column: 31] 2019-05-15 14:38:24.757 
    WARN 8964 --- [nio-8090-exec-3]
    .w.s.m.s.DefaultHandlerExceptionResolver : Resolved
    [org.springframework.http.converter.HttpMessageNotReadableException:
    JSON parse error: Unrecognized token 'eth': was expecting ('true',
    'false' or 'null'); nested exception is
    com.fasterxml.jackson.core.JsonParseException: Unrecognized token
    'eth': was expecting ('true', 'false' or 'null')  at [Source:
    (PushbackInputStream); line: 1, column: 31]]</p>
  </blockquote>