Table of Contents

Java Base64 MimeDecoder Methods

使用 MIME 解碼器，將字串解碼為二進位資料，字串必須屬於字元 A-Za-z0-9+/ 這 64 種字元組合，將忽略所有在 Base64 字母表中，找不到的行分隔符號或其他字元，此外也採用 Apache Commons Codec 的實用 API 進行解碼， Base64 MimeDecoder Java Methods 本篇增加了範例，並透過單元測試來驗證產出結果。

檔案目錄

./
   +- src
       +- test
       |   +- org
       |       +- ruoxue
       |           +- java_147
       |               +- base64
       |                   +- mime
       |                       +- Base64MimeDecoderMethodsTest.java

單元測試

Base64 MimeDecoder Methods Java 提供 MIME 解碼器操作，將字串解碼成二進位資料。

decode

建立一個 String ，轉成 byte[] ，使用 Base64.MimeDecoder 進行解碼。

	@Test
	public void decode() throws Exception {
		Base64.Decoder decoder = Base64.getMimeDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0\n"
				+ "NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4\n"
				+ "eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx\n"
				+ "cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv";
		System.out.println(value);
		byte[] result = decoder.decode(value.toString().getBytes(StandardCharsets.UTF_8.toString()));
		System.out.println(result);
		String stringResult = new String(result);
		System.out.println(stringResult);
		assertThat(stringResult).isEqualTo(
				"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
	}

QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0
NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4
eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx
cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv
[B@6aa8ceb6
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

decodeWithDst

Base64 MimeDecoder Methods Java 建立一個 String ，轉成 byte[] 使用 Base64.MimeDecoder 進行解碼，將結果存放到另一個陣列。

	@Test
	public void decodeWithDst() throws Exception {
		Base64.Decoder decoder = Base64.getMimeDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0\n"
				+ "NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4\n"
				+ "eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx\n"
				+ "cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv";
		System.out.println(value);
		int size = 512;
		byte[] dst = new byte[size];
		int result = decoder.decode(value.toString().getBytes(StandardCharsets.UTF_8.toString()), dst);
		System.out.println(result);
		String stringResult = new String(dst);
		System.out.println(stringResult);
		assertThat(stringResult).containsIgnoringWhitespaces(
				"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/")
				.hasSize(size);
	}

QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0
NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4
eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx
cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv
192
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

decodeWithByteBuffer

Base64 MimeDecoder Methods Java 建立一個 String ，轉成 byte[] 包裝成 ByteBuffer ，使用 Base64.MimeDecoder 進行解碼，傳回 ByteBuffer 。

	@Test
	public void decodeWithByteBuffer() throws Exception {
		Base64.Decoder decoder = Base64.getMimeDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0\n"
				+ "NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4\n"
				+ "eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx\n"
				+ "cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv";
		ByteBuffer byteBuffer = ByteBuffer.wrap(value.toString().getBytes(StandardCharsets.UTF_8.toString()));
		System.out.println(byteBuffer);
		ByteBuffer result = decoder.decode(byteBuffer);
		System.out.println(result);
		String stringResult = new String(result.array(), StandardCharsets.UTF_8.toString());
		System.out.println(stringResult);
		assertThat(stringResult).isEqualTo(
				"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
	}

java.nio.HeapByteBuffer[pos=0 lim=259 cap=259]
java.nio.HeapByteBuffer[pos=0 lim=192 cap=192]
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

Base64_decodeBase64

建立一個 String ，轉成 byte[] 使用 Apache Commons Codec 套件 Base64 進行解碼。

	@Test
	public void Base64_decodeBase64() throws Exception {
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0\n"
				+ "NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4\n"
				+ "eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx\n"
				+ "cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv";
		System.out.println(value);
		byte[] result = org.apache.commons.codec.binary.Base64
				.decodeBase64(value.getBytes(StandardCharsets.UTF_8.toString()));
		System.out.println(result);
		String stringResult = new String(result);
		System.out.println(stringResult);
		assertThat(stringResult).isEqualTo(
				"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
	}

QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0
NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4
eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx
cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv
[B@4c98385c
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

Base64_decodeBase64WithString

建立一個 String ，轉成 byte[] 使用 Apache Commons Codec 套件 Base64 進行解碼。

	@Test
	public void Base64_decodeBase64WithString() throws Exception {
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0\n"
				+ "NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4\n"
				+ "eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx\n"
				+ "cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv";
		System.out.println(value);
		byte[] result = org.apache.commons.codec.binary.Base64.decodeBase64(value);
		System.out.println(result);
		String stringResult = new String(result);
		System.out.println(stringResult);
		assertThat(stringResult).isEqualTo(
				"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
	}

QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0
NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4
eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx
cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv
[B@6bf2d08e
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

Base64MimeDecoderMethodsTest.java

Base64 MimeDecoder Methods in Java 新增單元測試，驗證 Base64 MimeDecoder Functions in Java 是否符合預期。

package org.ruoxue.java_147.base64.mime;

import static org.assertj.core.api.Assertions.assertThat;

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

import org.junit.Test;

public class Base64MimeDecoderMethodsTest {

	@Test
	public void decode() throws Exception {
		Base64.Decoder decoder = Base64.getMimeDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0\n"
				+ "NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4\n"
				+ "eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx\n"
				+ "cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv";
		System.out.println(value);
		byte[] result = decoder.decode(value.toString().getBytes(StandardCharsets.UTF_8.toString()));
		System.out.println(result);
		String stringResult = new String(result);
		System.out.println(stringResult);
		assertThat(stringResult).isEqualTo(
				"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
	}

	@Test
	public void decodeWithDst() throws Exception {
		Base64.Decoder decoder = Base64.getMimeDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0\n"
				+ "NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4\n"
				+ "eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx\n"
				+ "cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv";
		System.out.println(value);
		int size = 512;
		byte[] dst = new byte[size];
		int result = decoder.decode(value.toString().getBytes(StandardCharsets.UTF_8.toString()), dst);
		System.out.println(result);
		String stringResult = new String(dst);
		System.out.println(stringResult);
		assertThat(stringResult).containsIgnoringWhitespaces(
				"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/")
				.hasSize(size);
	}

	@Test
	public void decodeWithByteBuffer() throws Exception {
		Base64.Decoder decoder = Base64.getMimeDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0\n"
				+ "NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4\n"
				+ "eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx\n"
				+ "cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv";
		ByteBuffer byteBuffer = ByteBuffer.wrap(value.toString().getBytes(StandardCharsets.UTF_8.toString()));
		System.out.println(byteBuffer);
		ByteBuffer result = decoder.decode(byteBuffer);
		System.out.println(result);
		String stringResult = new String(result.array(), StandardCharsets.UTF_8.toString());
		System.out.println(stringResult);
		assertThat(stringResult).isEqualTo(
				"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
	}

	@Test
	public void decodeWithString() throws Exception {
		Base64.Decoder decoder = Base64.getMimeDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0\n"
				+ "NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4\n"
				+ "eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx\n"
				+ "cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv";
		System.out.println(value);
		byte[] result = decoder.decode(value);
		System.out.println(result);
		String stringResult = new String(result);
		System.out.println(stringResult);
		assertThat(stringResult).isEqualTo(
				"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
	}

	@Test
	public void Base64_decodeBase64() throws Exception {
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0\n"
				+ "NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4\n"
				+ "eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx\n"
				+ "cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv";
		System.out.println(value);
		byte[] result = org.apache.commons.codec.binary.Base64
				.decodeBase64(value.getBytes(StandardCharsets.UTF_8.toString()));
		System.out.println(result);
		String stringResult = new String(result);
		System.out.println(stringResult);
		assertThat(stringResult).isEqualTo(
				"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
	}

	@Test
	public void Base64_decodeBase64WithString() throws Exception {
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0\n"
				+ "NTY3ODkrL0FCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaYWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4\n"
				+ "eXowMTIzNDU2Nzg5Ky9BQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWmFiY2RlZmdoaWprbG1ub3Bx\n"
				+ "cnN0dXZ3eHl6MDEyMzQ1Njc4OSsv";
		System.out.println(value);
		byte[] result = org.apache.commons.codec.binary.Base64.decodeBase64(value);
		System.out.println(result);
		String stringResult = new String(result);
		System.out.println(stringResult);
		assertThat(stringResult).isEqualTo(
				"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
	}
}

心得分享

Base64 MimeDecoder Functions in Java 工具類別提供了一套靜態方法取得 MIME 解碼器，依照 RFC 2045 中指定的 Base64 字母表，將一組字元A-Za-z0-9+/ ，解碼成二進位資料，熟悉 Base64 MimeDecoder Methods in Java 這些方法的操作，提升開發效率，在應用上相當廣泛。