Java 使用正则表达式进行电子邮件验证

我发现我可以使用正则表达式验证电子邮件输入。然而，我不知道该把这些表达放在哪里。我是否将它们放在我的java控制器方法、实体类或JSP中？

如果您的电子邮件是字符串，您可以编写如下内容来验证电子邮件：

String email;
.
.  // load the email string
. 
if (email.matches("^[A-Za-z0-9_.]+[@][A-Za-z.]+$"))
{
.
.
.
}
else
    throw new EmailNotValidException();

---

我认为您可以创建一些

EmailValidatorClass

类，在需要验证电子邮件地址时，您可以在项目中使用这些类：

import javax.mail.internet.InternetAddress;
import javax.mail.internet.AddressException;
import java.util.StringTokenizer;

/**
  * A class to provide stronger validation of email addresses.      
  *
  */
 public class EmailAddressValidator
 {
   public static boolean isValidEmailAddress(String emailAddress)
   {
     // a null string is invalid
     if ( emailAddress == null )
       return false;

     // a string without a "@" is an invalid email address
     if ( emailAddress.indexOf("@") < 0 )
       return false;

     // a string without a "."  is an invalid email address
     if ( emailAddress.indexOf(".") < 0 )
       return false;

     if ( lastEmailFieldTwoCharsOrMore(emailAddress) == false )
       return false;

     try
     {
       InternetAddress internetAddress = new InternetAddress(emailAddress);
       return true;
     }
     vcatch (AddressException ae)
     {
       // log exception
            return false;
     }
   }


   /**
    * Returns true if the last email field (i.e., the country code, or something
    * like .com, .biz, .cc, etc.) is two chars or more in length, which it really
    * must be to be legal.
    */
   private static boolean lastEmailFieldTwoCharsOrMore(String emailAddress)
   {
     if (emailAddress == null) return false;
     StringTokenizer st = new StringTokenizer(emailAddress,".");
     String lastToken = null;
     while ( st.hasMoreTokens() )
     {
       lastToken = st.nextToken();
     }

     if ( lastToken.length() >= 2 )
     {
       return true;
     }
     else
     {
       return false;
     }
   }
 }

导入javax.mail.internet.InternetAddress；
导入javax.mail.internet.AddressException；
导入java.util.StringTokenizer；
/**
*提供更强的电子邮件地址验证的类。
*
*/
公共类EmailAddressValidator
{
公共静态布尔值isValidEmailAddress（字符串emailAddress）
{
//空字符串无效
如果（emailAddress==null）
返回false；
//没有“@”的字符串是无效的电子邮件地址
if（emailAddress.indexOf（“@”）<0）
返回false；
//没有“.”的字符串是无效的电子邮件地址
if（emailAddress.indexOf（“.”）小于0）
返回false；
if（lastEmailFieldTwoCharsOrMore（emailAddress）==false）
返回false；
尝试
{
InternetAddress InternetAddress=新的InternetAddress（电子邮件地址）；
返回true；
}
vcatch（地址异常ae）
{
//日志异常
返回false；
}
}
/**
*如果最后一个电子邮件字段（即国家代码或其他内容）为
*例如.com、.biz、.cc等）的长度为两个字符或更多，这实际上是
*必须是合法的。
*/
私有静态布尔lastEmailFieldTwoCharsOrMore（字符串emailAddress）
{
如果（emailAddress==null）返回false；
StringTokenizer st=新的StringTokenizer（电子邮件地址“.”）；
字符串lastToken=null；
而（st.hasMoreTokens（））
{
lastToken=st.nextToken（）；
}
如果（lastToken.length（）>=2）
{
返回true；
}
其他的
{
返回false；
}
}
}

仅使用正则表达式无法创建正确的电子邮件验证

下面介绍如何（几乎）正确验证电子邮件地址

---

电子邮件根据和进行验证。以下是电子邮件语法的简化形式定义：

addr-spec = local-part "@" domain
local-part = dot-atom-text / quoted-string
dot-atom-text = atom *("." atom)
atom = 1*atext
atext = ALPHA / DIGIT / "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "/" / "=" / "?" / "^" / "_" / "`" / "{" / "|" / "}" / "~"
ALPHA = ASCII characters in the range ‘a’ (ACSII code 0x61) through ‘z’ (ACSII code 0x7A) and ‘A’ (ACSII code 0x41) through ‘Z’ (ACSII code 0x5A)
DIGIT = ASCII characters in the range ‘0’ (ACSII code 0x30) through ‘9’ (ACSII code 0x39)
specials = "(" / ")" / "<" / ">" / "[" / "]" / ":" / ";" / "@" / "\" / "," / "."
quoted-string = “ *(qcontent) “
qcontent = qtext / quoted-pair
qtext = 0x21 / 0x23-0x5B / 0x5D-0x7E; All ASCII printable characters instead of “ and \
quoted-pair = \ (VCHAR / WSP)
VCHAR = 0x21-0x7E; All ASCII printable characters
WSP = 0x20 / 0x09; ASCII Space or tab characters

另外，将域限制为255个ASCII符号，将标签限制为63个ASCII符号

---

Apache commons验证库（在问题的评论中提到）是一个良好的开端。它包含域验证和电子邮件验证，尽管上次我检查时，它在电子邮件验证中有一些错误。

为什么不使用commons validator？请参考以下问题，给出一些比例：@Artefactor commons validator？这是进口货还是进口货？我是java新手>@RUi，不过你得使用一个额外的库。

addr-spec = local-part "@" domain
local-part = dot-atom-text / quoted-string
dot-atom-text = atom *("." atom)
atom = 1*atext
atext = ALPHA / DIGIT / "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "/" / "=" / "?" / "^" / "_" / "`" / "{" / "|" / "}" / "~"
ALPHA = ASCII characters in the range ‘a’ (ACSII code 0x61) through ‘z’ (ACSII code 0x7A) and ‘A’ (ACSII code 0x41) through ‘Z’ (ACSII code 0x5A)
DIGIT = ASCII characters in the range ‘0’ (ACSII code 0x30) through ‘9’ (ACSII code 0x39)
specials = "(" / ")" / "<" / ">" / "[" / "]" / ":" / ";" / "@" / "\" / "," / "."
quoted-string = “ *(qcontent) “
qcontent = qtext / quoted-pair
qtext = 0x21 / 0x23-0x5B / 0x5D-0x7E; All ASCII printable characters instead of “ and \
quoted-pair = \ (VCHAR / WSP)
VCHAR = 0x21-0x7E; All ASCII printable characters
WSP = 0x20 / 0x09; ASCII Space or tab characters

domain = subdomain / " " 
subdomain = label / subdomain "." label
label = let-dig *(*(ldh-str) let-dig)
ldh-str = let-dig-hyp / let-dig-hyp ldh-str
let-dig-hyp = let-dig / "-"
let-dig = ALPHA / DIGIT