http超链接获取图片转base64字符串，把base64字符串保存为本地文件，及读取base64文件

package org.jeecg.common.util;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;

public class Base64ImageUtil {

    /**
     * 超链接获取图片 转base64字符串
     * @param imageUrl 超链接
     * @return
     */
    public static String getURLImage(String imageUrl) {
        String base64String = "";
        try {
            //new一个URL对象
            URL url = new URL(imageUrl);
            //打开链接
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            //设置请求方式为"GET"
            conn.setRequestMethod("GET");
            //超时响应时间为5秒
            conn.setConnectTimeout(5 * 1000);
            //通过输入流获取图片数据
            InputStream inStream = conn.getInputStream();
            //得到图片的二进制数据，以二进制封装得到数据，具有通用性
            byte[] data = readInputStream(inStream);
            BASE64Encoder encode = new BASE64Encoder();
            base64String = encode.encode(data);

        } catch (Exception e) {
            e.printStackTrace();
        }
        return base64String;
    }

    /**
     * 把base64字符串转换成文件保存到本地
     * @param base64String
     * @param filePath
     * @param fileName
     * @throws IOException
     */
    public static void convertBase64ToFile(String base64String, String filePath, String fileName) throws IOException {
        File file = null;
        File filedir = new File(filePath);
        if (!filedir.exists()) {
            filedir.mkdirs();
        }
        file = new File(filePath + File.separator + fileName);
        if (file.exists()){
            file.delete();
        }
        BASE64Decoder decoder = new BASE64Decoder();

        // Base64解码,对字节数组字符串进行Base64解码并生成文件
        byte[] byt = decoder.decodeBuffer(base64String);
        for (int i = 0, len = byt.length; i < len; ++i) {
            // 调整异常数据
            if (byt[i] < 0) {
                byt[i] += 256;
            }
        }
        OutputStream out = null;
        InputStream input = new ByteArrayInputStream(byt);
        try {
            // 生成指定格式的文件
            out = new FileOutputStream(filePath + File.separator + fileName);
            byte[] buff = new byte[1024];
            int len = 0;
            while ((len = input.read(buff)) != -1) {
                out.write(buff, 0, len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            out.flush();
            out.close();
        }
    }


    /**
     * 把文件转为base64字符串
     * @param filePath
     * @return
     */
    public static String readBase64File(String filePath) {
        String StringBase64 = "";
        File file = null;

        file = new File(filePath);
        if (!file.exists()){
            return StringBase64;
        }
        InputStream in = null;
        byte[] data = null;
        // 读取文件字节数组
        try {
            in = new FileInputStream(filePath);
            data = new byte[in.available()];
            in.read(data);
            in.close();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                in.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        // 对字节数组Base64编码
        BASE64Encoder encoder = new BASE64Encoder();
        // 返回 Base64 编码过的字节数组字符串
        return encoder.encode(data);
    }

    private static byte[] readInputStream(InputStream inStream) throws Exception {
        ByteArrayOutputStream outStream = new ByteArrayOutputStream();
        //创建一个Buffer字符串
        byte[] buffer = new byte[1024];
        //每次读取的字符串长度，如果为-1，代表全部读取完毕
        int len = 0;
        //使用一个输入流从buffer里把数据读取出来
        while ((len = inStream.read(buffer)) != -1) {
            //用输出流往buffer里写入数据，中间参数代表从哪个位置开始读，len代表读取的长度
            outStream.write(buffer, 0, len);
        }
        //关闭输入流
        inStream.close();
        //把outStream里的数据写入内存
        return outStream.toByteArray();
    }


}

 

//获取图片转base64字符串
base64String = getURLImage(httppath); 
//保存到本地
convertBase64ToFile(base64String, filepath, fileName);

读取base64文件为字符串
 String imgBase64 = "data:image/jpeg;base64," + readBase64File(filepath);