问Spring CustomAuthenticationProvider authentication.getName()返回空字符串

EN

<div class="login">

    <h3>Login with Username and Password</h3>

    <c:url value="/j_spring_security_check" var="loginUrl" />
    <form name='loginForm' action="${loginUrl}" method="post">
        <table>
            <tr>
                <td>Username:</td>
                <td><input type='text' name='username'></td>
            </tr>
            <tr>
                <td>Password:</td>
                <td><input type='password' name='password' /></td>
            </tr>
            <tr>
                <td colspan='2'>
                    <c:choose>
                        <c:when test="${showLoginForm}">
                            <% System.out.println( "Showing Login Form"); %>
                            <input name="submit" type="submit" value="Login" />
                        </c:when>
                        <c:otherwise>
                         <% System.out.println( "Showing Logout Form"); %>
                            <c:url value="/j_spring_security_logout" var="logoutUrl" />
                            <input type="button" onClick="location.href='${logoutUrl}'" value="Logout">
                        </c:otherwise>
                    </c:choose>
                </td>
            </tr>
            <tr>
                <td>
                    <button type="submit" class="btn">Log in2</button>
                </td>
            </tr>
        </table>
        <input type="hidden" name="${_csrf.parameterName}" value="${_csrf.token}" />
    </form>

    <c:if test="${not empty error}">
        <div class="error">${error}</div>
    </c:if>
    <c:if test="${not empty loggedIn}">
        <div class="loggedIn">${loggedIn}</div>
    </c:if>
    <c:if test="${not empty loggedOut}">
        <div class="loggedOut">${loggedOut}</div>
    </c:if>

</div>

    package com.craig.spring;

    import org.springframework.security.authentication.AuthenticationProvider;
    import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
    import org.springframework.security.core.Authentication;
    import org.springframework.security.core.AuthenticationException;

    public class CustomAuthenticationProvider implements AuthenticationProvider{

@Override
public Authentication authenticate(Authentication authentication)throws AuthenticationException {
    // TODO Auto-generated method stub
    authentication.getCredentials(); //returns ""
    authentication.getName(); //returns ""
    return authentication;
}

@Override
public boolean supports(Class<?> authentication) {
    //return false;
    return UsernamePasswordAuthenticationToken.class.isAssignableFrom(authentication);
}

    }

    <?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
<display-name>League</display-name>
<welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<servlet>
    <servlet-name>spring</servlet-name>
    <servlet-class>
        org.springframework.web.servlet.DispatcherServlet
    </servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>spring</servlet-name>
    <url-pattern>/</url-pattern>
</servlet-mapping>
<servlet-mapping>
    <servlet-name>default</servlet-name>
    <url-pattern>*.css</url-pattern>
</servlet-mapping>
<servlet-mapping>
    <servlet-name>default</servlet-name>
    <url-pattern>*.js</url-pattern>
</servlet-mapping>
<servlet-mapping>
    <servlet-name>default</servlet-name>
    <url-pattern>*.gif</url-pattern>
</servlet-mapping>
<servlet-mapping>
    <servlet-name>default</servlet-name>
    <url-pattern>*.jpg</url-pattern>
</servlet-mapping>
<servlet-mapping>
    <servlet-name>default</servlet-name>
    <url-pattern>*.png</url-pattern>
</servlet-mapping>

<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>
        /WEB-INF/spring-security.xml
    </param-value>
</context-param>

<!-- Spring Security -->
<filter>
    <filter-name>springSecurityFilterChain</filter-name>
    <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
</filter>

<filter-mapping>
    <filter-name>springSecurityFilterChain</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

    <beans:beans xmlns="http://www.springframework.org/schema/security"
xmlns:beans="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/security
http://www.springframework.org/schema/security/spring-security-3.2.xsd">

<http auto-config="true" disable-url-rewriting="true" entry-point-ref="loginUrlAuthenticationEntryPoint">
</http>

<beans:bean id="loginUrlAuthenticationEntryPoint"
    class="org.springframework.security.web.authentication.LoginUrlAuthenticationEntryPoint">
    <beans:property name="loginFormUrl" value="/login.html"/>
</beans:bean>

<beans:bean id="customAuthenticationProvider" class="com.craig.spring.CustomAuthenticationProvider"  />

<authentication-manager>
    <authentication-provider ref="customAuthenticationProvider" />
</authentication-manager>