java如何通过url地址的到文件对象呢？(史上最全代码)

实现思路:
    1.读取文件对象
	2.借助Stream对象将文件对象转换为byte

    /**
     * 远程读取文件
     *
     * @param netUrl
     * @return
     */
    public static File getNetUrl(String netUrl) {
        //判断http和https
        File file = null;
        if (netUrl.startsWith("https://")) {
            file = getNetUrlHttps(netUrl);
        } else {
            file = getNetUrlHttp(netUrl);
        }
        return file;
    }

全部引用的包，工具类可能有其他引用，取自己所需的路径就好
import com.java265.core.util.other.X509TrustUtiil;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItem;
import org.apache.commons.io.IOUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.commons.CommonsMultipartFile;
 
import javax.net.ssl.*;
import javax.servlet.http.HttpServletRequest;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.nio.channels.FileChannel;
import java.util.*;

getNetUrlHttp方法
这里创建的是本地临时文件，所以用完了之后，不用刻意调用file.delete方法进行删除

public static File getNetUrlHttp(String netUrl) {
        //对本地文件命名
        String fileName = StringUtils.reloadFile(netUrl);
        File file = null;
 
 
        URL urlfile;
        InputStream inStream = null;
        OutputStream os = null;
        try {
            file = File.createTempFile("net_url", fileName);
            //下载
            urlfile = new URL(netUrl);
            inStream = urlfile.openStream();
            os = new FileOutputStream(file);
 
            int bytesRead = 0;
            byte[] buffer = new byte[8192];
            while ((bytesRead = inStream.read(buffer, 0, 8192)) != -1) {
                os.write(buffer, 0, bytesRead);
            }
        } catch (Exception e) {
            log.error("远程图片获取错误："+netUrl);
            e.printStackTrace();
        } finally {
            try {
                if (null != os) {
                    os.close();
                }
                if (null != inStream) {
                    inStream.close();
                }
 
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
 
        return file;
    }

getNetUrlHttps
这个方法就相对于要麻烦很多了，毕竟涉及到ssl，很多人再请求的时候绕不开ssl，这里可以通过代码进行处理

SSLContext不需要其他包，使用java自带的，无需import
/**
     * 下载文件到本地(支持https)
     *
     * @param fileUrl 远程地址
     * @throws Exception
     */
 
    public static File getNetUrlHttps(String fileUrl) {
        //对本地文件进行命名
        String file_name = StringUtils.reloadFile(fileUrl);
        File file = null;
 
        DataInputStream in = null;
        DataOutputStream out = null;
        try {
            file = File.createTempFile("net_url", file_name);
 
            SSLContext sslcontext = SSLContext.getInstance("SSL", "SunJSSE");
            sslcontext.init(null, new TrustManager[]{new X509TrustUtiil()}, new java.security.SecureRandom());
            URL url = new URL(fileUrl);
            HostnameVerifier ignoreHostnameVerifier = new HostnameVerifier() {
                @Override
                public boolean verify(String s, SSLSession sslsession) {
                    logger.warn("WARNING: Hostname is not matched for cert.");
                    return true;
                }
            };
            HttpsURLConnection.setDefaultHostnameVerifier(ignoreHostnameVerifier);
            HttpsURLConnection.setDefaultSSLSocketFactory(sslcontext.getSocketFactory());
            HttpsURLConnection urlCon = (HttpsURLConnection) url.openConnection();
            urlCon.setConnectTimeout(6000);
            urlCon.setReadTimeout(6000);
            int code = urlCon.getResponseCode();
            if (code != HttpURLConnection.HTTP_OK) {
                throw new Exception("文件读取失败");
            }
            // 读文件流
            in = new DataInputStream(urlCon.getInputStream());
            out = new DataOutputStream(new FileOutputStream(file));
            byte[] buffer = new byte[2048];
            int count = 0;
            while ((count = in.read(buffer)) > 0) {
                out.write(buffer, 0, count);
            }
            out.close();
            in.close();
        } catch (Exception e) {
            log.error("远程图片获取错误："+fileUrl);
            e.printStackTrace();
        } finally {
            try {
                if (null != out) {
                    out.close();
                }
                if (null != in) {
                    in.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
 
        return file;
    }

其中X509TrustUtiil的工具包

import javax.net.ssl.X509TrustManager;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
 
public class X509TrustUtiil implements X509TrustManager {
 
	@Override
	public void checkClientTrusted(X509Certificate[] arg0, String arg1) throws CertificateException {
		// TODO Auto-generated method stub
 
	}
 
	@Override
	public void checkServerTrusted(X509Certificate[] arg0, String arg1) throws CertificateException {
		// TODO Auto-generated method stub
 
	}
 
	@Override
	public X509Certificate[] getAcceptedIssuers() {
		return null;
	}
 
}

StringUtils工具类:
/**
     * 重命名，UUIU
     *
     * @param oleFileName
     * @return
     */
    public static String reloadFile(String oleFileName) {
        oleFileName = getFileName(oleFileName);
        if (StringUtils.isEmpty(oleFileName)) {
            return oleFileName;
        }
        //得到后缀
        if (oleFileName.indexOf(".") == -1) {
            //对于没有后缀的文件，直接返回重命名
            return UniqId.getUid();
        }
        String[] arr = oleFileName.split("\\.");
        // 根据uuid重命名图片
        String fileName = UniqId.getUid() + "." + arr[arr.length - 1];
 
        return fileName;
    }
 
    /**
     * 把带路径的文件地址解析为真实文件名 /test/test888.jpg 解析为 test888.jpg
     *
     * @param url
     */
    public static String getFileName(final String url) {
        if (StringUtils.isEmpty(url)) {
            return url;
        }
        String newUrl = url;
        newUrl = newUrl.split("[?]")[0];
        String[] bb = newUrl.split("/");
        String fileName = bb[bb.length - 1];
        return fileName;
    }