Not specifying example causes warn log message with stacktrace for longs

[PascalSchumacher]

Simplified example:

@Api(tags = "Tag value")
@RestController
@RequestMapping(path = "/path", produces = MediaType.APPLICATION_JSON_VALUE)
public class Controller {

    @ApiOperation("Lists all ...")
    @GetMapping
    public Page<MyObject> method(
        @ApiParam("Results page") 
        @RequestParam(required=false, defaultValue="1")
        Integer page) {
        // code
    }
}

causes:

018-04-25 10:20:49.747  WARN 16832 --- [nio-8888-exec-9] i.s.m.p.AbstractSerializableParameter    : Illegal DefaultValue 1 for parameter type integer

java.lang.NumberFormatException: For input string: ""
	at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) ~[na:1.8.0_121]
	at java.lang.Long.parseLong(Long.java:601) ~[na:1.8.0_121]
	at java.lang.Long.valueOf(Long.java:803) ~[na:1.8.0_121]
	at io.swagger.models.parameters.AbstractSerializableParameter.getExample(AbstractSerializableParameter.java:395) ~[swagger-models-1.5.18.jar:1.5.18]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_121]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_121]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_121]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_121]
	at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:688) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serializeContents(IndexedListSerializer.java:119) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serialize(IndexedListSerializer.java:79) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serialize(IndexedListSerializer.java:18) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.std.MapSerializer.serializeFields(MapSerializer.java:718) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.std.MapSerializer.serialize(MapSerializer.java:639) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.std.MapSerializer.serialize(MapSerializer.java:33) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider._serialize(DefaultSerializerProvider.java:480) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:319) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ObjectMapper._configAndWriteValue(ObjectMapper.java:3893) [jackson-databind-2.9.5.jar:2.9.5]
	at com.fasterxml.jackson.databind.ObjectMapper.writeValueAsString(ObjectMapper.java:3207) [jackson-databind-2.9.5.jar:2.9.5]
	at springfox.documentation.spring.web.json.JsonSerializer.toJson(JsonSerializer.java:38) [springfox-spring-web-2.9.0.jar:2.9.0]
	at springfox.documentation.swagger2.web.Swagger2Controller.getDocumentation(Swagger2Controller.java:105) [springfox-swagger2-2.9.0.jar:2.9.0]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_121]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_121]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_121]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_121]
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209) [spring-web-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) [spring-web-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) [spring-webmvc-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:877) [spring-webmvc-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:783) [spring-webmvc-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) [spring-webmvc-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991) [spring-webmvc-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925) [spring-webmvc-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974) [spring-webmvc-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:866) [spring-webmvc-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:635) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851) [spring-webmvc-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-embed-websocket-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) [spring-web-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_121]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_121]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at java.lang.Thread.run(Thread.java:745) [na:1.8.0_121]

I'm using swagger-core 1.5.18, but the code in the 1.5 branch should have the same behavior.

This issue is similar to #1568 and could be fixed similar to #1586

(For reference: I originally reported this issue to Springfox in: springfox/springfox#2377)

[rainoko]

should change the code
In AbstractSerializableParameter.java

@JsonProperty("x-example")
    public Object getExample() {
        if (example == null) {
            return null;
        }

This should check also that if example is empty string should return null.
Empty string is default value for example in annotation
ApiParam.java

So it causing lot of warnings in log.

[breeze02]

I am also suffering for a similar problem.

I think that this problem isn't caused by empty string.
Please see the following log message.

"i.s.m.p.AbstractSerializableParameter : Illegal DefaultValue 1 for parameter type integer"

Although 1 is legal DefaultValue for integer, swagger couldn't recognize it.

It doesn't happen with swagger-models 1.5.14. And It happens with swagger-models 1.5.20.

[frantuma]

warning fixed in #2784.