[Exception] HttpMessageNotReadableException

org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: No suitable constructor found for type [simple type, class cn.jintongsoft.cloud.web.bean.NeglectBean$P]: can not instantiate from JSON object (need to add/enable type information?)
 at [Source: java.io.PushbackInputStream@a7e5a9c; line: 1, column: 12] (through reference chain: cn.jintongsoft.cloud.web.bean.NeglectBean["pairs"]->java.util.ArrayList[0]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: No suitable constructor found for type [simple type, class cn.jintongsoft.cloud.web.bean.NeglectBean$P]: can not instantiate from JSON object (need to add/enable type information?)
 at [Source: java.io.PushbackInputStream@a7e5a9c; line: 1, column: 12] (through reference chain: cn.jintongsoft.cloud.web.bean.NeglectBean["pairs"]->java.util.ArrayList[0])
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:208) ~[spring-web-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:200) ~[spring-web-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver.readWithMessageConverters(AbstractMessageConverterMethodArgumentResolver.java:146) ~[spring-webmvc-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.readWithMessageConverters(RequestResponseBodyMethodProcessor.java:167) ~[spring-webmvc-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.resolveArgument(RequestResponseBodyMethodProcessor.java:102) ~[spring-webmvc-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:77) ~[spring-web-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:162) ~[spring-web-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:129) ~[spring-web-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) ~[spring-webmvc-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776) ~[spring-webmvc-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705) ~[spring-webmvc-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[spring-webmvc-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) ~[spring-webmvc-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) ~[spring-webmvc-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967) [spring-webmvc-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:869) [spring-webmvc-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:647) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843) [spring-webmvc-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter.doFilterInternal(OpenEntityManagerInViewFilter.java:178) [spring-orm-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:85) [spring-web-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310) [tomcat-embed-core-7.0.37.jar:7.0.37]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_112]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_112]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_112]
Caused by: com.fasterxml.jackson.databind.JsonMappingException: No suitable constructor found for type [simple type, class cn.jintongsoft.cloud.web.bean.NeglectBean$P]: can not instantiate from JSON object (need to add/enable type information?)
 at [Source: java.io.PushbackInputStream@a7e5a9c; line: 1, column: 12] (through reference chain: cn.jintongsoft.cloud.web.bean.NeglectBean["pairs"]->java.util.ArrayList[0])
    at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:148) ~[jackson-databind-2.4.6.jar:2.4.6]
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1071) ~[jackson-databind-2.4.6.jar:2.4.6]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:264) ~[jackson-databind-2.4.6.jar:2.4.6]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:124) ~[jackson-databind-2.4.6.jar:2.4.6]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:232) ~[jackson-databind-2.4.6.jar:2.4.6]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:206) ~[jackson-databind-2.4.6.jar:2.4.6]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:25) ~[jackson-databind-2.4.6.jar:2.4.6]
    at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:538) ~[jackson-databind-2.4.6.jar:2.4.6]
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:99) ~[jackson-databind-2.4.6.jar:2.4.6]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:306) ~[jackson-databind-2.4.6.jar:2.4.6]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:124) ~[jackson-databind-2.4.6.jar:2.4.6]
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3066) ~[jackson-databind-2.4.6.jar:2.4.6]
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2221) ~[jackson-databind-2.4.6.jar:2.4.6]
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:205) ~[spring-web-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    ... 42 common frames omitted

解决方案：为对应的类声明空构造器