发这篇博文的题目可能无法直接表示内容,但是确实是java.sql.Date和java.util.Date.
今天在使用‘net.sf.json.JSONObject‘封装json数据的时候,碰到很奇怪的问题,报出的异常,让我开始觉得,不知道从哪个异常开始找解决方案,报错如下:
一月 30, 2015 11:14:49 上午 org.apache.catalina.core.StandardWrapperValve invoke SEVERE: Servlet.service() for servlet [spt.servlet.JsonServlet] in context with path [/ServerAQI] threw exception net.sf.json.JSONException: java.lang.reflect.InvocationTargetException at net.sf.json.JSONObject._fromBean(JSONObject.java:953) at net.sf.json.JSONObject.fromObject(JSONObject.java:192) at net.sf.json.JSONObject._processValue(JSONObject.java:2774) at net.sf.json.JSONObject._setInternal(JSONObject.java:2798) at net.sf.json.JSONObject.setValue(JSONObject.java:1507) at net.sf.json.JSONObject._fromBean(JSONObject.java:940) at net.sf.json.JSONObject.fromObject(JSONObject.java:192) at net.sf.json.JSONObject._processValue(JSONObject.java:2774) at net.sf.json.JSONObject.processValue(JSONObject.java:2833) at net.sf.json.JSONObject.element(JSONObject.java:1871) at net.sf.json.JSONObject.element(JSONObject.java:1849) at net.sf.json.JSONObject.put(JSONObject.java:2466) at spt.service.JsonService.getJsonStr(JsonService.java:12) at spt.servlet.JsonServlet.doPost(JsonServlet.java:34) at spt.servlet.JsonServlet.doGet(JsonServlet.java:53) at javax.servlet.http.HttpServlet.service(HttpServlet.java:620) at javax.servlet.http.HttpServlet.service(HttpServlet.java:727) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) at spt.servlet.filter.EncodingFilter.doFilter(EncodingFilter.java:24) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611) at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2466) at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2455) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:722) Caused by: java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at org.apache.commons.beanutils.PropertyUtilsBean.invokeMethod(PropertyUtilsBean.java:1773) at org.apache.commons.beanutils.PropertyUtilsBean.getSimpleProperty(PropertyUtilsBean.java:1132) at org.apache.commons.beanutils.PropertyUtilsBean.getNestedProperty(PropertyUtilsBean.java:686) at org.apache.commons.beanutils.PropertyUtilsBean.getProperty(PropertyUtilsBean.java:715) at org.apache.commons.beanutils.PropertyUtils.getProperty(PropertyUtils.java:290) at net.sf.json.JSONObject._fromBean(JSONObject.java:928) ... 40 more Caused by: java.lang.IllegalArgumentException at java.sql.Date.getHours(Date.java:182) ... 50 more
通常,我们有两种思路找解决方案:从我们自定义类中开始找错.
这种思路是我在网上看教程视频,一个讲师说的,蛮实用的.但是一开始的时候,我并没有这样做(其实我应该这样做).我先是查 ‘java.lang.IllegalArgumentException java.sql.Date.getHours),发现有个哥们写的一大篇中文,但觉得他说的都不怎么对.
又一次觉得 stackoverflow上的哥们真的很厉害.
我们知道,java.sql.Date是java.util.Date的子类,所以我们无需显示将java.sql.Date转换为java.util.Date.
在jdbc中,使用PreparedStatement往数据库中存储date的时候,我们需要将java.util.Date转换为java.sql.Date.
java.sql.Date在数据库中存储的是不带time部分的,所以将java.sql.Date转换为java.util.Date的时候,应该使用 ResultSet..getTimestamp("currentDate"), 而不能让其隐式转换(ref:Converting java.sql.Date to java.util.Date)
当我使用ResultSet..getTimestamp("currentDate")将java.sql.Date转换为java.util.Date的时候,就能将json数据正常封装了.