问题：java.lang.NumberFormatException: null
解决办法：
小程序使用request方法时的content-type改成"application/x-www-form-urlencoded"
代码如下：
//test.js
wx.request({
url: "xxxxxx",
method: 'POST',
data:{ "testId": testId},
header: {
'content-type': 'application/x-www-form-urlencoded',
},
success: (res) => {
console.log(res)
},
})
//Test.java
String Id = request.getParameter("testId");
详细说明：
我将请求头的类型修改成"application/x-www-form-urlencoded"之后，获取的值不为null的原因，可通过两种请求头的区别找出来
（1）application/x-www-form-urlencoded
是浏览器的原生 form 表单，如果不设置 enctype 属性，那么最终就会以 application/x-www-form-urlencoded 方式提交数据。提交的数据按照 key1=val1&key2=val2 的方式进行编码，key 和 val 都进行了 URL 转码。
（2）application/json
把它作为请求头，是用来告诉服务端消息主体是序列化后的 JSON 字符串。
我在后台是使用"request.getParameter(“testId”)"来获取值，而它获取的类型正是 key1=val1&key2=val2的形式，因此将请求头改成“application/x-www-form-urlencoded”就可以解决这个问题了
详细错误：
java.lang.NumberFormatException: null
at java.lang.Integer.parseInt(Integer.java:454)
at java.lang.Integer.parseInt(Integer.java:527)
at com.szearth.servlet.PushMessage.doPost(PushMessage.java:55)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
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 com.szearth.filter.EncodeFilter.doFilter(EncodeFilter.java:28)
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:218)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:962)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:452)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1087)
at org.apache.coyote.AbstractProtocolAbstractConnectionHandler.process(AbstractProtocol.java:637)atorg.apache.tomcat.util.net.AprEndpointAbstractConnectionHandler.process(AbstractProtocol.java:637)atorg.apache.tomcat.util.net.AprEndpointSocketProcessor.doRun(AprEndpoint.java:2536)
at org.apache.tomcat.util.net.AprEndpointSocketProcessor.run(AprEndpoint.java:2525)atjava.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)atjava.util.concurrent.ThreadPoolExecutorSocketProcessor.run(AprEndpoint.java:2525)atjava.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)atjava.util.concurrent.ThreadPoolExecutorWorker.run(ThreadPoolExecutor.java:615)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:744)
文章最后发布于: 2019-09-29
