摘要：用于統(tǒng)一編碼格式。由于和內(nèi)置的遵守的協(xié)議不一致，按照照實(shí)現(xiàn)的，是按照和兩個(gè)協(xié)議來實(shí)現(xiàn)的。由于協(xié)議的不同可能導(dǎo)致的解碼編碼的數(shù)據(jù)時(shí)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(gè)需求，需要根據(jù)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(jìn)行編碼轉(zhuǎn)碼存儲(chǔ)。

采用了兩個(gè)工具類：ImageUtil和Base64Util。ImageUtil用于實(shí)際操作。Base64Util用于統(tǒng)一編碼格式。

由于jdk1.7和jdk1.8內(nèi)置的Base64遵守的RFC協(xié)議不一致，jdk1.7按照照RFC1521實(shí)現(xiàn)的，jdk1.8是按照rfc4648和rfc2045兩個(gè)協(xié)議來實(shí)現(xiàn)的。具體可以從類注釋中查詢到。由于協(xié)議的不同可能導(dǎo)致jdk1.8的解碼jdk1.7編碼的數(shù)據(jù)時(shí)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(jié)果包含換行；
jdk8的編碼結(jié)果不包含換行；
jdk8無法解碼包含換行的編碼結(jié)果;

既然得知上述異常產(chǎn)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(jìn)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(zhuǎn)文件地址
     *
     * @param filePath
     * @param base64
     * @param fileName
     */
    public static void base64ToImg(String filePath, String base64, String fileName) {
        File file = null;
        //創(chuàng)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(jìn)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(chuàng)建一個(gè)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(gè)輸入流從buffer里把數(shù)據(jù)讀取出來
            while ((len = is.read(buffer)) != -1) {
                // 用輸出流往buffer里寫入數(shù)據(jù)，中間參數(shù)代表從哪個(gè)位置開始讀，len代表讀取的長度
                outStream.write(buffer, 0, len);
            }
            // 對(duì)字節(jié)數(shù)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(zhuǎn)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(zhuǎn)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("");
    }
}