我想解码Base64编码的字符串,然后将它存储在我的数据库中。如果输入不是Base64编码的,我需要抛出一个错误。
我如何检查一个字符串是否被Base64编码?
我想解码Base64编码的字符串,然后将它存储在我的数据库中。如果输入不是Base64编码的,我需要抛出一个错误。
我如何检查一个字符串是否被Base64编码?
当前回答
您可以使用以下正则表达式来检查字符串是否构成有效的base64编码:
^([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{2}==)?$
在base64编码中,字符集为[A-Z, A-Z, 0-9和+ /]。如果其余长度小于4,则字符串用'='字符填充。
^([A-Za-z0-9+/]{4})*表示字符串以0个或多个base64组开头。
([A-Za-z0-9 + /] {4} | [A-Za-z0-9 + /] {3} = | [A-Za-z0-9 + /]{2} = =)意味着美元的字符串以三种形式之一:A-Za-z0-9 + / {4}, {3} = [A-Za-z0-9 + /]或[A-Za-z0-9 + /]{2} = =。
其他回答
试试这个:
public void checkForEncode(String string) {
String pattern = "^([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{4}|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{2}==)$";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(string);
if (m.find()) {
System.out.println("true");
} else {
System.out.println("false");
}
}
Function Check_If_Base64(ByVal msgFile As String) As Boolean
Dim I As Long
Dim Buffer As String
Dim Car As String
Check_If_Base64 = True
Buffer = Leggi_File(msgFile)
Buffer = Replace(Buffer, vbCrLf, "")
For I = 1 To Len(Buffer)
Car = Mid(Buffer, I, 1)
If (Car < "A" Or Car > "Z") _
And (Car < "a" Or Car > "z") _
And (Car < "0" Or Car > "9") _
And (Car <> "+" And Car <> "/" And Car <> "=") Then
Check_If_Base64 = False
Exit For
End If
Next I
End Function
Function Leggi_File(PathAndFileName As String) As String
Dim FF As Integer
FF = FreeFile()
Open PathAndFileName For Binary As #FF
Leggi_File = Input(LOF(FF), #FF)
Close #FF
End Function
import java.util.Base64;
public static String encodeBase64(String s) {
return Base64.getEncoder().encodeToString(s.getBytes());
}
public static String decodeBase64(String s) {
try {
if (isBase64(s)) {
return new String(Base64.getDecoder().decode(s));
} else {
return s;
}
} catch (Exception e) {
return s;
}
}
public static boolean isBase64(String s) {
String pattern = "^([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{4}|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{2}==)$";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(s);
return m.find();
}
这在Python中是有效的:
def is_base64(string):
if len(string) % 4 == 0 and re.test('^[A-Za-z0-9+\/=]+\Z', string):
return(True)
else:
return(False)
如果解码时我们得到一个包含ASCII字符的字符串,则字符串为 不编码
(RoR) ruby解决方案:
def encoded?(str)
Base64.decode64(str.downcase).scan(/[^[:ascii:]]/).count.zero?
end
def decoded?(str)
Base64.decode64(str.downcase).scan(/[^[:ascii:]]/).count > 0
end