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【原】发送http请求，报错：Cannot write output after reading input.

不忘初心 2019-03-12 围观() 评论() 点赞() 【JAVA开发】

简介：最近对接一个第三方，有专门的系统来对接，我们直接对接内部的系统即可，但是调用接口时，发现一直报错：Cannot write output after readi

最近对接一个第三方，有专门的系统来对接，我们直接对接内部的系统即可，但是调用接口时，发现一直报错：Cannot write output after reading input，大概意思是不能在读取了输入流之后去写输出流。

起初还以为是对接第三方报错了，仔细检查一番，竟然是同事的代码写的有问题，开启了两次输出流。

错误信息如下：

2019-03-12 11:51:03,717 ERROR TongDunManager: [ApiInvoker] invoke throw exception, details: java.net.ProtocolException: Cannot write output after reading input.
        at sun.net.www.protocol.http.HttpURLConnection.getOutputStream0(HttpURLConnection.java:1330)
        at sun.net.www.protocol.http.HttpURLConnection.getOutputStream(HttpURLConnection.java:1309)
        at sun.net.www.protocol.https.HttpsURLConnectionImpl.getOutputStream(HttpsURLConnectionImpl.java:259)
        at com.st.gateway.project.biz.tongdun.TongDunManager.invoke(TongDunManager.java:175)
        at com.st.gateway.project.biz.tongdun.TongDunManager.ktpTaskQuery(TongDunManager.java:99)
        at com.st.gateway.project.web.rest.TongDunCallbackController.lambda$ktp$0(TongDunCallbackController.java:32)
        at com.st.gateway.common.core.biz.RestBusinessTemplate.doExecute(RestBusinessTemplate.java:66)
        at com.st.gateway.common.core.biz.RestBusinessTemplate.execute(RestBusinessTemplate.java:23)
        at com.st.gateway.project.web.rest.TongDunCallbackController.ktp(TongDunCallbackController.java:27)
        at com.st.gateway.project.web.rest.TongDunCallbackController$FastClassBySpringCGLIB$78ded699.invoke(<generated>)
        at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
        at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:738)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
        at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:85)
        at com.st.gateway.common.base.aop.ApiDigestInterceptor.invoke(ApiDigestInterceptor.java:31)
        at sun.reflect.GeneratedMethodAccessor110.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)

错误代码片段：

conn = (HttpURLConnection) url.openConnection();
conn.setRequestProperty("Connection", "Keep-Alive");
conn.setConnectTimeout(1000);
conn.setReadTimeout(3000);
conn.setRequestMethod("POST");
conn.setDoOutput(true);
conn.getOutputStream().write(postBody.toString().getBytes());
conn.getOutputStream().flush();
int responseCode = conn.getResponseCode();
if (responseCode != 200) {
    return null;
}

错误的地方，我用红色框起来

发送http请求，报错：Cannot write output after reading input.

在开始没看代码之前，查阅了一些资料，资料中也有类似的问题，比如：在getOutputStream()之前执行getResponseCode()，这样也会有同样的错误。

更改之后的代码如下：

conn = (HttpURLConnection) url.openConnection();
conn.setRequestProperty("Connection", "Keep-Alive");
conn.setConnectTimeout(5000);
conn.setReadTimeout(5000);
conn.setRequestMethod("POST");
conn.setDoOutput(true);
OutputStream os = conn.getOutputStream();
os.write(postBody.toString().getBytes());
os.flush();
int responseCode = conn.getResponseCode();
if (responseCode != 200) {
    return null;
}