在工作中我们有时会遇到需要在request中获取请求参数的场景。比如说用来记录追踪日志，排查问题等。
本篇文章主要介绍的是在springboot框架下输出到日志的使用场景。
一、当HTTP请求方式为get或delete时，有以下几种方式：
1.获取url中所有参数
request.getQueryString()；
2.获取指定某个参数：
String value=request.getparameter("key");
2.request.getParameterMap();
Enumeration enu=request.getParameterNames();
while(enu.hasMoreElements()){
String paraName=(String)enu.nextElement();
System.out.println(paraName+": "+request.getParameter(paraName));
}
3.request.getParameterNames();
Map map=request.getParameterMap();
Set keSet=map.entrySet();
for(Iterator itr=keSet.iterator();itr.hasNext();){
Map.Entry me=(Map.Entry)itr.next();
Object ok=me.getKey();
Object ov=me.getValue();
String[] value=new String[1];
if(ov instanceof String[]){
value=(String[])ov;
}else{
value[0]=ov.toString();
}
for(int k=0;k<value.length;k++){
System.out.println(ok+"="+value[k]);
}
}
二、当HTTP请求方式为post、patch、put等时，有以下几种方式：
因为此时请求参数位于request中的body中，而java提供的requset中没有直接可以获取body信息的方法。那么我们可通过IO流的方式来获取，详情如下：
1.request.getReader()
//通过request.getReader()的方式来获取body
public static String getBodyMsg(HttpServletRequest request)
{
BufferedReader br = null;
StringBuilder sb = new StringBuilder("");
try
{
br = request.getReader();
String str;
while ((str = br.readLine()) != null)
{
sb.append(str);
}
br.close();
}
catch (IOException e)
{
e.printStackTrace();
}
finally
{
if (null != br)
{
try
{
br.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
return sb.toString();
}
2.request.getInputStream()
通过getInputStream()方法有两种方式：
//通过request.getInputStream()的方式来获取body信息
//方式一： IO流
public static void getBodyMsg(HttpServletRequest request)
{
InputStream is = null;
try
{
is = request.getInputStream();
StringBuilder sb = new StringBuilder();
byte[] b = new byte[4096];
for (int n; (n = is.read(b)) != -1;)
{
sb.append(new String(b, 0, n));
}
}
catch (IOException e)
{
e.printStackTrace();
}
finally
{
if (null != is)
{
try
{
is.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
}
//方式二：二进制的方式
public static byte[] getBodyBytes(HttpServletRequest request)
{
int len = request.getContentLength();
byte[] buffer = new byte[len];
ServletInputStream in = null;
try
{
in = request.getInputStream();
in.read(buffer, 0, len);
in.close();
}
catch (IOException e)
{
e.printStackTrace();
}
finally
{
if (null != in)
{
try
{
in.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
//也可以直接将byte[]转换为字符串返回
return buffer;
}
注意事项：
1.IO流使用完后记得关闭资源。
2.request中的body内容，通过流的方式只能调用一次。也就是request.getReader()，request.getInputStream()和request.getparameter(“key”)这三种方法，只能读取一次，如果再次读取就会报Stream closed的错误，错误信息如下：
org.springframework.http.converter.HttpMessageNotReadableException: I/O error while reading input message; nested exception is java.io.IOException: Stream closed
at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver.readWithMessageConverters(AbstractMessageConverterMethodArgumentResolver.java:229)
at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.readWithMessageConverters(RequestResponseBodyMethodProcessor.java:150)
at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.resolveArgument(RequestResponseBodyMethodProcessor.java:128)
at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121)
at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:158)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:128)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:661)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.io.IOException: Stream closed
at org.apache.catalina.connector.InputBuffer.readByte(InputBuffer.java:334)
at org.apache.catalina.connector.CoyoteInputStream.read(CoyoteInputStream.java:93)
at java.io.FilterInputStream.read(FilterInputStream.java:83)
at java.io.PushbackInputStream.read(PushbackInputStream.java:139)
at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver$EmptyBodyCheckingHttpInputMessage.<init>(AbstractMessageConverterMethodArgumentResolver.java:324)
at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver.readWithMessageConverters(AbstractMessageConverterMethodArgumentResolver.java:189)
... 41 common frames omitted
总结一下其实就是因为IO流关闭只能读取一次。读过之后，再来读取，就没有了。就像水流一样。这怎么办呢？
我们可以将读出来的内容保存起来后，再将它放回去，这样就不会影响下次使用了。
下一篇将着重介绍如何解决该方法。