java编/解码

August 4, 2022

URL 编/解码

application/x-www-form-urlencoded

java

import java.net.URLDecoder;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;

public class Main {
    public static void main(String[] args) {
        // 此函数需要指定编码
        String encoded = URLEncoder.encode("中文", StandardCharsets.UTF_8);
        System.out.println(encoded); // => %E4%B8%AD%E6%96%87

        String decoded = URLDecoder.decode("%E4%B8%AD%E6%96%87", StandardCharsets.UTF_8);
        System.out.println(decoded); // => 中文
    }
}

注意这两个函数都有一个字符编码可指定为字符串的重载函数，但会抛出异常，故不推荐
应当始终使用 UTF-8 编码

java

try {
    String encoded = URLEncoder.encode("中文", "utf-8");
    String decoded = URLDecoder.decode("%E4%B8%AD%E6%96%87", "UTF-8");
} catch (UnsupportedEncodingException e) {
    // ...
}

Base64 编/解码

java

import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.Base64;

public class Main {
    public static void main(String[] args) {
        Base64.Encoder base64Encoder = Base64.getEncoder(); // 编码器
        Base64.Decoder base64Decoder = Base64.getDecoder(); // 解码器

        byte[] originalBytes = new byte[]{-28, -72, -83, -26, -106, -121};
        // 相当于： "中文".getBytes(StandardCharsets.UTF_8)

        // 编码为字节数组
        byte[] encodedBytes = base64Encoder.encode(originalBytes);
        // 编码为字符串
        String encodedString = base64Encoder.encodeToString(originalBytes);

        System.out.println(Arrays.toString(originalBytes)); // => [-28, -72, -83, -26, -106, -121]
        System.out.println(Arrays.toString(encodedBytes)); // => [53, 76, 105, 116, 53, 112, 97, 72]
        System.out.println(encodedString); // => 5Lit5paH
        // 下面的方法将字节数组转换为String
        System.out.println(new String(encodedBytes, StandardCharsets.UTF_8)); // => 5Lit5paH


        // 解码方法是一个重载方法
        byte[] decodedBytes1 = base64Decoder.decode("5Lit5paH");
        byte[] decodedBytes2 = base64Decoder.decode(encodedBytes);
        System.out.println(Arrays.toString(decodedBytes1)); // => [-28, -72, -83, -26, -106, -121]
        System.out.println(Arrays.toString(decodedBytes2)); // => [-28, -72, -83, -26, -106, -121]
        System.out.println(new String(decodedBytes1, StandardCharsets.UTF_8)); // => 中文


        // 还可以通过withoutPadding方法获取一个不添加末尾`=`的编码器（无需对应解码器）
        Base64.Encoder encoder2 = Base64.getEncoder().withoutPadding();

        // 获取适用于URL的Base64变种编/解码器
        Base64.Encoder encoder3 = Base64.getUrlEncoder();
        Base64.Decoder decoder3 = Base64.getUrlDecoder();

        // 获取适用于Mime的Base64变种编/解码器
        Base64.Encoder encoder4 = Base64.getMimeEncoder();
        Base64.Decoder decoder4 = Base64.getMimeDecoder();
    }
}

具体参见文档：https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/Base64.html

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This work is licensed under CC BY-NC-SA 4.0