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Java Base64 Decoder Methods - Java 147

Java Base64 Decoder Methods – Java 147

Java Base64 Decoder Methods

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，否則無法解碼，會拋出 IllegalArgumentException: Illegal base64 character ，此外也採用 Apache Commons Codec 的實用 API 進行解碼， Base64 Decoder 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
       |                   +- basic
       |                       +- Base64DecoderMethodsTest.java

單元測試

Base64 Decoder Methods Java 提供 Base64 基本解碼器操作，將字串解碼成二進位資料。

decode

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

	@Test
	public void decode() throws Exception {
		Base64.Decoder decoder = Base64.getDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==";
		System.out.println(value);
		byte[] result = decoder.decode(value.getBytes(StandardCharsets.UTF_8.toString()));
		System.out.println(result);
		String stringResult = new String(result);
		System.out.println(stringResult);
		assertThat(stringResult).isEqualTo("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
	}
QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==
[B@32a1bec0
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

decodeWithoutPadding

Base64 Decoder Methods Java 建立一個 String ，編碼不進行填充 ，轉成 byte[] ，使用 Base64.Decoder 解碼。

	@Test
	public void decodeWithoutPadding() throws Exception {
		Base64.Decoder decoder = Base64.getDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw";
		System.out.println(value);
		byte[] result = decoder.decode(value.getBytes(StandardCharsets.UTF_8.toString()));
		System.out.println(result);
		String stringResult = new String(result);
		System.out.println(stringResult);
		assertThat(stringResult).isEqualTo("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
	}
QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw
[B@32a1bec0
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

decodeWithDst

Base64 Decoder Methods Java 建立一個 String ，轉成 byte[] 使用 Base64.Decoder 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.getDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==";
		System.out.println(value);
		int size = 100;
		byte[] dst = new byte[size];
		int result = decoder.decode(value.getBytes(StandardCharsets.UTF_8.toString()), dst);
		System.out.println(result);
		String stringResult = new String(dst);
		System.out.println(stringResult);
		assertThat(stringResult)
				.containsIgnoringWhitespaces("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/")
				.hasSize(size);
	}
QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==
64
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

decodeWithByteBuffer

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

	@Test
	public void decodeWithByteBuffer() throws Exception {
		Base64.Decoder decoder = Base64.getDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==";
		ByteBuffer byteBuffer = ByteBuffer.wrap(value.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+/");
	}
java.nio.HeapByteBuffer[pos=0 lim=88 cap=88]
java.nio.HeapByteBuffer[pos=0 lim=64 cap=64]
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

decodeWithString

Base64 Decoder Methods 建立一個 String ， 使用 Base64.Decoder 進行解碼。

	@Test
	public void decodeWithString() throws Exception {
		Base64.Decoder decoder = Base64.getDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==";
		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+/
QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==

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 = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==";
		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+/");
	}
QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==
[B@1a93a7ca
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 = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==";
		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+/");
	}
QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==
[B@2b05039f
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

Base64DecoderMethodsTest.java

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

package org.ruoxue.java_147.base64.basic;

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 Base64DecoderMethodsTest {

	@Test
	public void decode() throws Exception {
		Base64.Decoder decoder = Base64.getDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==";
		System.out.println(value);
		byte[] result = decoder.decode(value.getBytes(StandardCharsets.UTF_8.toString()));
		System.out.println(result);
		String stringResult = new String(result);
		System.out.println(stringResult);
		assertThat(stringResult).isEqualTo("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
	}

	@Test
	public void decodeWithoutPadding() throws Exception {
		Base64.Decoder decoder = Base64.getDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw";
		System.out.println(value);
		byte[] result = decoder.decode(value.getBytes(StandardCharsets.UTF_8.toString()));
		System.out.println(result);
		String stringResult = new String(result);
		System.out.println(stringResult);
		assertThat(stringResult).isEqualTo("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
	}

	@Test
	public void decodeWithDst() throws Exception {
		Base64.Decoder decoder = Base64.getDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==";
		System.out.println(value);
		int size = 100;
		byte[] dst = new byte[size];
		int result = decoder.decode(value.getBytes(StandardCharsets.UTF_8.toString()), dst);
		System.out.println(result);
		String stringResult = new String(dst);
		System.out.println(stringResult);
		assertThat(stringResult)
				.containsIgnoringWhitespaces("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/")
				.hasSize(size);
	}

	@Test
	public void decodeWithByteBuffer() throws Exception {
		Base64.Decoder decoder = Base64.getDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==";
		ByteBuffer byteBuffer = ByteBuffer.wrap(value.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+/");
	}

	@Test
	public void decodeWithString() throws Exception {
		Base64.Decoder decoder = Base64.getDecoder();
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==";
		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+/");
	}

	@Test
	public void Base64_decodeBase64() throws Exception {
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==";
		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+/");
	}

	@Test
	public void Base64_decodeBase64WithString() throws Exception {
		String value = "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ejAxMjM0NTY3ODkrLw==";
		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+/");
	}
}

心得分享

Base64 Decoder Functions in Java 工具類別提供了一套靜態方法取得基本解碼器，依照 RFC 4648 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 Decoder Methods in Java 這些方法的操作，提升開發效率，在應用上相當廣泛。

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