There is no PasswordEncoder mapped for the id “null”

1、问题描述：在写基于Spring cloud微服务的OAuth2认证服务时，因为Spring-Security从4+升级到5+，导致There is no PasswordEncoder mapped for the id “null”错误。

2、解决方案：

可在密码验证类中添加

@Bean
public static NoOpPasswordEncoder passwordEncoder() {
  return (NoOpPasswordEncoder) NoOpPasswordEncoder.getInstance();
}

或者在xml配置文件中添加

<b:bean id="passwordEncoder"
        class="org.springframework.security.crypto.password.NoOpPasswordEncoder" factory-method="getInstance"/>

Spring官方文

3、拓展：源码解读：Class PasswordEncoderFactories，Spring Security 5 新增加了多种密码加密方式。

当前版本5新增支持加密方式：

bcrypt - BCryptPasswordEncoder (Also used for encoding)
ldap - LdapShaPasswordEncoder
MD4 - Md4PasswordEncoder
MD5 - new MessageDigestPasswordEncoder("MD5")
noop - NoOpPasswordEncoder
pbkdf2 - Pbkdf2PasswordEncoder
scrypt - SCryptPasswordEncoder
SHA-1 - new MessageDigestPasswordEncoder("SHA-1")
SHA-256 - new MessageDigestPasswordEncoder("SHA-256")
sha256 - StandardPasswordEncoder