HTTP Status 400 – Bad Request
Type Status Report
Description The server cannot or will not process the request due to something that is perceived to be a client error (., malformed request syntax, invalid request message framing, or deceptive request routing).
Apache Tomcat/8.5.12
解决：restful的增删对应的http方法分别为put及delete（边跑步边想到的。。。）
调用put方法步骤
1.修改tomcat下conf/
<servlet>
<servlet-name>default</servlet-name>
<servlet-class></servlet-class>
<init-param>
<param-name>debug</param-name>
<param-value>0</param-value>
</init-param>
<init-param>
<param-name>listings</param-name>
<param-value>false</param-value>
</init-param>
<init-param> //主要是这里，默认的readonly属性是true，即不支持put方法，改为false
<param-name>readonly</param-name>
<param-value>false</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet> 这段代码若中已经存在就修改上面readonly节点属性即可，若没有就新加。 2.修改tomcat目录下conf/，添加用户权限，同时调用接口时也需要加上同下的权限。
<?xml version='1.0' encoding='cp1252'?>
<tomcat-users>
<user name="admin" password="admin" roles="admin" />
</tomcat-users> 3.修改工程项目下的
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="/xml/ns/javaee"
xmlns:xsi="http:///2001/XMLSchema-instance"
xsi:schemaLocation="/xml/ns/javaee
/xml/ns/javaee/web-app_2_5.xsd"
version="2.5">
<security-constraint>
<web-resource-collection>
<web-resource-name>Demo App</web-resource-name>
<url-pattern>/*</url-pattern>
<http-method>PUT</http-method>
</web-resource-collection>
<auth-constraint>
<role-name>admin</role-name>
</auth-constraint>
</security-constraint>
<login-config>
<auth-method>BASIC</auth-method>
<realm-name>Demo App</realm-name>
</login-config>
<security-role>
<description>Role for restricted resources</description>
<role-name>admin</role-name>
</security-role>
</web-app> 新加以上代码。 至此即可调用put方法。