摘要：用于統一編碼格式。由于和內置的遵守的協議不一致，按照照實現的，是按照和兩個協議來實現的。由于協議的不同可能導致的解碼編碼的數據時拋出異常因此需要特別注意保持解碼編碼的一致性。

最近工作上有個需求，需要根據圖片的url下載到本地，并且客戶端無法訪問到url只能接收base64圖片碼。因此決定采用jdk自帶的Base64進行編碼轉碼存儲。

采用了兩個工具類：ImageUtil和Base64Util。ImageUtil用于實際操作。Base64Util用于統一編碼格式。

由于jdk1.7和jdk1.8內置的Base64遵守的RFC協議不一致，jdk1.7按照照RFC1521實現的，jdk1.8是按照rfc4648和rfc2045兩個協議來實現的。具體可以從類注釋中查詢到。由于協議的不同可能導致jdk1.8的解碼jdk1.7編碼的數據時拋出java.lang.IllegalArgumentException: Illegal base64 character a異常.因此需要特別注意保持解碼編碼的一致性。
jdk7的編碼結果包含換行；
jdk8的編碼結果不包含換行；
jdk8無法解碼包含換行的編碼結果;

既然得知上述異常產生的由于,故找到解決方案也很簡單。

使用apache common包中的org.apache.commons.codec.binary.Base64類進行編碼和解碼；

編碼之后或解碼之前去除換行符；

編碼和解碼使用相同的jdk版本；

ImageUtils

import javax.imageio.ImageIO;
import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;

public class ImageUtils {

    /**
     * base64轉文件地址
     *
     * @param filePath
     * @param base64
     * @param fileName
     */
    public static void base64ToImg(String filePath, String base64, String fileName) {
        File file = null;
        //創建文件目錄
        File dir = new File(filePath);
        if (!dir.exists() && !dir.isDirectory()) {
            dir.mkdirs();
        }
        BufferedOutputStream bos = null;
        java.io.FileOutputStream fos = null;
        try {
            byte[] bytes = Base64Util.decode(base64);
            file = new File(filePath + fileName);
            fos = new java.io.FileOutputStream(file);
            bos = new BufferedOutputStream(fos);
            bos.write(bytes);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (bos != null) {
                try {
                    bos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (fos != null) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    /**
     * 通過Toolkit獲取base64
     *
     * @param url
     * @return
     * @author caoting
     * @date 2018年11月21日
     */
    public static String getBase64ByImgUrl(String url) {
        String suffix = url.substring(url.lastIndexOf(".") + 1);
        try {
            URL urls = new URL(url);
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            Image image = Toolkit.getDefaultToolkit().getImage(urls);
            BufferedImage biOut = toBufferedImage(image);
            ImageIO.write(biOut, suffix, baos);
            String base64Str = Base64Util.encode(baos.toByteArray());
            return base64Str;
        } catch (Exception e) {
            return "";
        }

    }

    public static BufferedImage toBufferedImage(Image image) {
        if (image instanceof BufferedImage) {
            return (BufferedImage) image;
        }
        // This code ensures that all the pixels in the image are loaded
        image = new ImageIcon(image).getImage();
        BufferedImage bimage = null;
        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
        try {
            int transparency = Transparency.OPAQUE;
            GraphicsDevice gs = ge.getDefaultScreenDevice();
            GraphicsConfiguration gc = gs.getDefaultConfiguration();
            bimage = gc.createCompatibleImage(image.getWidth(null), image.getHeight(null), transparency);
        } catch (HeadlessException e) {
            // The system does not have a screen
        }
        if (bimage == null) {
            // Create a buffered image using the default color model
            int type = BufferedImage.TYPE_INT_RGB;
            bimage = new BufferedImage(image.getWidth(null), image.getHeight(null), type);
        }
        // Copy image to buffered image
        Graphics g = bimage.createGraphics();
        // Paint the image onto the buffered image
        g.drawImage(image, 0, 0, null);
        g.dispose();
        return bimage;
    }

    /**
     * 通過下載二進制流的方式獲取base64
     *
     * @param imgUrl 圖片url
     * @return 返回圖片base64的字符串
     */
    public static String image2Base64(String imgUrl) {

        URL url = null;
        InputStream is = null;
        ByteArrayOutputStream outStream = null;

        HttpURLConnection httpUrl = null;
        try {

            url = new URL(imgUrl);
            httpUrl = (HttpURLConnection) url.openConnection();
            httpUrl.connect();

            httpUrl.getInputStream();
            is = httpUrl.getInputStream();
            outStream = new ByteArrayOutputStream();

            // 創建一個Buffer字符串
            byte[] buffer = new byte[1024];
            // 每次讀取的字符串長度，如果為-1，代表全部讀取完畢
            int len = 0;
            // 使用一個輸入流從buffer里把數據讀取出來
            while ((len = is.read(buffer)) != -1) {
                // 用輸出流往buffer里寫入數據，中間參數代表從哪個位置開始讀，len代表讀取的長度
                outStream.write(buffer, 0, len);
            }
            // 對字節數組Base64編碼
            return Base64Util.encode(outStream.toByteArray());

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (outStream != null) {
                try {
                    outStream.close();

                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (httpUrl != null) {
                httpUrl.disconnect();
            }
        }
        return imgUrl;
    }
}

Base64Util

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

import javax.imageio.stream.FileImageInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Base64Util{
    /**
     * 字符串轉圖片
     * @param base64Str
     * @return
     */
    public static byte[] decode(String base64Str){
        byte[] b = null;
        BASE64Decoder decoder = new BASE64Decoder();
        try {
            b = decoder.decodeBuffer(replaceEnter(base64Str));
        } catch (IOException e) {
            e.printStackTrace();
        }
        return b;
    }

    /**
     * 圖片轉字符串
     * @param image
     * @return
     */
    public static String encode(byte[] image){
        BASE64Encoder decoder = new BASE64Encoder();
        return replaceEnter(decoder.encode(image));
    }

    public static String encode(String uri){
        BASE64Encoder encoder = new BASE64Encoder();
        return replaceEnter(encoder.encode(uri.getBytes()));
    }

    /**
     *
     * @path    圖片路徑
     * @return
     */

    public static byte[] imageTobyte(String path){
        byte[] data = null;
        FileImageInputStream input = null;
        try {
            input = new FileImageInputStream(new File(path));
            ByteArrayOutputStream output = new ByteArrayOutputStream();
            byte[] buf = new byte[1024];
            int numBytesRead = 0;
            while((numBytesRead = input.read(buf)) != -1){
                output.write(buf, 0, numBytesRead);
            }
            data = output.toByteArray();
            output.close();
            input.close();

        } catch (Exception e) {
            e.printStackTrace();
        }

        return data;
    }

    public static String replaceEnter(String str){
        String reg ="[
-
]";
        Pattern p = Pattern.compile(reg);
        Matcher m = p.matcher(str);
        return m.replaceAll("");
    }
}