base64前端对登陆密码编码，后端解码

一，前端 JS

<script>
 
    // base64加密开始  
    var keyStr = "ABCDEFGHIJKLMNOP" + "QRSTUVWXYZabcdef" + "ghijklmnopqrstuv"  
            + "wxyz0123456789+/" + "=";  
      
    function encode64(input) {  
  
        var output = "";  
        var chr1, chr2, chr3 = "";  
        var enc1, enc2, enc3, enc4 = "";  
        var i = 0;  
        do {  
            chr1 = input.charCodeAt(i++);  
            chr2 = input.charCodeAt(i++);  
            chr3 = input.charCodeAt(i++);  
            enc1 = chr1 >> 2;  
            enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);  
            enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);  
            enc4 = chr3 & 63;  
            if (isNaN(chr2)) {  
                enc3 = enc4 = 64;  
            } else if (isNaN(chr3)) {  
                enc4 = 64;  
            }  
            output = output + keyStr.charAt(enc1) + keyStr.charAt(enc2)  
                    + keyStr.charAt(enc3) + keyStr.charAt(enc4);  
            chr1 = chr2 = chr3 = "";  
            enc1 = enc2 = enc3 = enc4 = "";  
        } while (i < input.length);  
  
        return output;  
    }  
    // base64加密结束  
 
 
 
    var oBtn = document.getElementById('btn');
    oBtn.onclick = function(){
         alert("按钮触发！");
         alert(encode64("abcdef"));
         console.log(encode64("abcdef"));
    };
    
</script>

调用：

 

二.后端解码

 

 

2.1. 自己编写解码实现

import java.io.ByteArrayOutputStream;
 
public class Base {
 
    private static byte[] base64DecodeChars = new byte[] { -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59,
            60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
            10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1,
            -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37,
            38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1,
            -1, -1 };
 
    /**
     * 解密
     * 
     * @param str
     * @return
     */
    public static String decode(String str) {
        byte[] data = str.getBytes();
        int len = data.length;
        ByteArrayOutputStream buf = new ByteArrayOutputStream(len);
        int i = 0;
        int b1, b2, b3, b4;
 
        while (i < len) {
            do {
                b1 = base64DecodeChars[data[i++]];
            } while (i < len && b1 == -1);
            if (b1 == -1) {
                break;
            }
 
            do {
                b2 = base64DecodeChars[data[i++]];
            } while (i < len && b2 == -1);
            if (b2 == -1) {
                break;
            }
            buf.write((int) ((b1 << 2) | ((b2 & 0x30) >>> 4)));
 
            do {
                b3 = data[i++];
                if (b3 == 61) {
                    return new String(buf.toByteArray());
                }
                b3 = base64DecodeChars[b3];
            } while (i < len && b3 == -1);
            if (b3 == -1) {
                break;
            }
            buf.write((int) (((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));
 
            do {
                b4 = data[i++];
                if (b4 == 61) {
                    return new String(buf.toByteArray());
                }
                b4 = base64DecodeChars[b4];
            } while (i < len && b4 == -1);
            if (b4 == -1) {
                break;
            }
            buf.write((int) (((b3 & 0x03) << 6) | b4));
        }
        return new String(buf.toByteArray());
    }
 
}