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使用GET方法，访问GET接口，服务端返回405

发生场景：
复制的POST请求代码，手动修改为GET，没有修改彻底，导致错误。

错误代码：

public class GET405 {public static void main(String[] args) {try {String defURL = "https://httpbin.org/get";URL url = new URL(defURL);// 打开和URL之间的连接HttpURLConnection con = (HttpURLConnection) url.openConnection();con.setRequestMethod("GET");//请求get方式con.setDoInput(true);// 默认值为 truecon.setDoOutput(true);//默认值为 false，传body参数必须写// 得到请求的输出流对象OutputStreamWriter writer = new OutputStreamWriter(con.getOutputStream(), "UTF-8");String body = "username=xiaohu&password=123456";writer.write(body);writer.flush();//            System.out.println("http请求方法:"+con.getRequestMethod());System.out.println("http状态码:" + con.getResponseCode());// 获取服务端响应，通过输入流来读取URL的响应InputStream is = con.getInputStream();BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));StringBuffer sbf = new StringBuffer();String strRead = null;while ((strRead = reader.readLine()) != null) {sbf.append(strRead);sbf.append("\r\n");}reader.close();// 关闭连接con.disconnect();// 打印读到的响应结果System.out.println("运行结束：" + sbf.toString());} catch (Exception e) {e.printStackTrace();}}
}

报错log:

405原因：
con.getOutputStream() 会把原有的GET方法改为POST方法，用POST方法访问GET接口，就报错405。看jdk1.8中HttpURLConnection的getOutpuStream()方法的源码：

解决办法：删掉getOutputStream()，用url传参。

正确代码：

public class GET200 {public static void main(String[] args) {try {String defURL = "https://httpbin.org/get";String body = "username=xiaohu&password=123456";URL url = new URL(defURL+"?"+body);// 打开和URL之间的连接HttpURLConnection con = (HttpURLConnection) url.openConnection();con.setRequestMethod("GET");//请求get方式//          System.out.println("http请求方法:"+con.getRequestMethod());System.out.println("http状态码:" + con.getResponseCode());// 获取服务端响应，通过输入流来读取URL的响应InputStream is = con.getInputStream();BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));StringBuffer sbf = new StringBuffer();String strRead = null;while ((strRead = reader.readLine()) != null) {sbf.append(strRead);sbf.append("\r\n");}reader.close();// 关闭连接con.disconnect();// 打印读到的响应结果System.out.println("运行结束：" + sbf.toString());} catch (Exception e) {e.printStackTrace();}}
}

运行结果：

http状态码:200
运行结束：{"args": {"password": "123456", "username": "xiaohu"}, "headers": {"Accept": "text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2", "Host": "httpbin.org", "User-Agent": "Java/1.8.0_221", "X-Amzn-Trace-Id": "Root=1-668a1ba0-278338c97b93d6ca4276c0b0"}, "origin": "113.57.25.151", "url": "https://httpbin.org/get?username=xiaohu&password=123456"
}

使用GET方法，访问POST接口，服务端返回405

发生场景：接口文档显示接口为GET接口，实际上后端人员写的是POST接口，文档没同步。

错误代码：

public class GETtoPOST405 {public static void main(String[] args) {try {String defURL = "https://httpbin.org/post";String body="username=xiaohu&password=123456";URL url = new URL(defURL + "?" + body);HttpURLConnection con = (HttpURLConnection) url.openConnection();
//          con.setUseCaches(false); // Post请求不能使用缓存con.setRequestMethod("GET");//请求get方式con.setDoInput(true);// 设置是否从HttpURLConnection输入，默认值为 truecon.setDoOutput(false);// 设置是否使用HttpURLConnection进行输出，默认值为 falseint code = con.getResponseCode();System.out.println("http状态码:" + code);if (code == HttpURLConnection.HTTP_OK) {System.out.println("测试成功");} else {System.out.println("测试失败：" + code);}// 获取服务端响应，通过输入流来读取URL的响应InputStream is = con.getInputStream();BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));StringBuffer sbf = new StringBuffer();String strRead = null;while ((strRead = reader.readLine()) != null) {sbf.append(strRead);sbf.append("\r\n");}reader.close();// 关闭连接con.disconnect();// 打印读到的响应结果System.out.println("运行结束：" + sbf.toString());} catch (Exception e) {e.printStackTrace();}}
}

报错log:

http状态码:405
测试失败：405Caused by: java.io.IOException: Server returned HTTP response code: 405 for URL: https://httpbin.org/post?username=xiaohu&password=123456

405原因：不知道后端接口的定义，或者没有沟通彻底，或者后端开发人员失误，本应该是GET定义成了POST。应该使用POST方法。

解决方法：使用POST请求。

正确代码：

public class POSTtoPOST200 {public static void main(String[] args) {try {String defURL = "https://httpbin.org/post";URL url = new URL(defURL);HttpURLConnection con = (HttpURLConnection) url.openConnection();
//          con.setUseCaches(false); // Post请求不能使用缓存con.setRequestMethod("POST");//请求POST方式con.setDoOutput(true);// 设置是否使用HttpURLConnection进行输出，默认值为 falseOutputStreamWriter writer = new OutputStreamWriter(con.getOutputStream(), "UTF-8");String body = "username=xiaohu&password=123456";writer.write(body);writer.flush();int code = con.getResponseCode();System.out.println("http状态码:" + code);if (code == HttpURLConnection.HTTP_OK) {System.out.println("测试成功");} else {System.out.println("测试失败：" + code);}// 获取服务端响应，通过输入流来读取URL的响应InputStream is = con.getInputStream();BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));StringBuffer sbf = new StringBuffer();String strRead = null;while ((strRead = reader.readLine()) != null) {sbf.append(strRead);sbf.append("\r\n");}reader.close();// 关闭连接con.disconnect();// 打印读到的响应结果System.out.println("运行结束：" + sbf.toString());} catch (Exception e) {e.printStackTrace();}}
}

运行结果：

http状态码:200
测试成功
运行结束：{"args": {}, "data": "", "files": {}, "form": {"password": "123456", "username": "xiaohu"}, "headers": {"Accept": "text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2", "Content-Length": "31", "Content-Type": "application/x-www-form-urlencoded", "Host": "httpbin.org", "User-Agent": "Java/1.8.0_221", "X-Amzn-Trace-Id": "Root=1-668a2091-2a64856935929fab74082ce4"}, "json": null, "origin": "113.57.25.151", "url": "https://httpbin.org/post"
}

使用POST方法，访问GET接口，服务端返回405

发生场景：代码失误，本该写GET，写成了POST。

错误代码：

public class POSTtoGET405 {public static void main(String[] args) {try {String defURL = "https://httpbin.org/get";URL url = new URL(defURL);// 打开和URL之间的连接HttpURLConnection con = (HttpURLConnection) url.openConnection();con.setRequestMethod("POST");//请求post方式
//            con.setUseCaches(false); // Post请求不能使用缓存con.setDoInput(true);// 设置是否从HttpURLConnection输入，默认值为 truecon.setDoOutput(true);// 设置是否使用HttpURLConnection进行输出，默认值为 falseOutputStreamWriter writer = new OutputStreamWriter(con.getOutputStream(), "UTF-8");String body = "username=xiaohu&password=123456";writer.write(body);writer.flush();writer.close();int code = con.getResponseCode();System.out.println("http状态码:" + code);if (code == HttpURLConnection.HTTP_OK) {System.out.println("测试成功");} else {System.out.println("测试失败：" + code);}// 获取服务端响应，通过输入流来读取URL的响应InputStream is = con.getInputStream();BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));StringBuffer sbf = new StringBuffer();String strRead = null;while ((strRead = reader.readLine()) != null) {sbf.append(strRead);sbf.append("\r\n");}reader.close();// 关闭连接con.disconnect();// 打印读到的响应结果System.out.println("运行结束：" + sbf.toString());} catch (Exception e) {e.printStackTrace();}}
}

405原因： 接口只接受GET方法，请求是POST方法。

错误场景：后端开发定义失误，本该是POST接口，写成了GET。接口没有测试。

解决办法：用GET访问。正确代码和GET访问GET一样。