java.lang.IllegalStateException: getWriter() has already been called for this response问题解决

java.lang.IllegalStateException: getWriter() has already been called for this response

在执行下述代码时报错，

OutputStream out = getResponse().getOutputStream();

原因为代码中有打开的Response.getWriter()，未关闭，因调用点较多，不好一一排查。

通过查看代码，看到response中的usingWriter=true，随即想办法将该标志位设置为false。

response.reset(); 即可，注意reset后缓存消失，设置消失。

OutputStream和Writer在一个response中不能同时获得。

具体内容见：

public static void filedownShowEX(String fileName, String filePath,HttpServletRequest request, HttpServletResponse response)
throws Exception {}

方法如下：

package com.fh.util;import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.OutputStream;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;/*** 文件处理 创建人：BYL 创建时间：2014年12月23日*/
public class FileUtils {public static void filedown(String fileName, String filePath,HttpServletRequest request, HttpServletResponse response) {try {// 得到该文件File file = new File(filePath + fileName);if (!file.exists()) {System.out.println("Have no such file!");return;// 文件不存在就退出方法}FileInputStream fileInputStream = new FileInputStream(file);// 设置Http响应头告诉浏览器下载这个附件String userAgent = request.getHeader("User-Agent");// 针对IE或者以IE为内核的浏览器：if (userAgent.contains("MSIE") || userAgent.contains("Trident")) {fileName = java.net.URLEncoder.encode(fileName, "UTF-8");} else {// 非IE浏览器的处理：fileName = new String(fileName.getBytes("UTF-8"), "ISO-8859-1");}response.setHeader("Content-disposition",String.format("attachment; filename=\"%s\"", fileName));response.setContentType("application/vnd.ms-excel;charset=utf-8");response.setCharacterEncoding("UTF-8");OutputStream outputStream = response.getOutputStream();byte[] bytes = new byte[2048];int len = 0;while ((len = fileInputStream.read(bytes)) > 0) {outputStream.write(bytes, 0, len);}fileInputStream.close();outputStream.close();} catch (Exception e) {// TODO: handle exception}}/*** 文件下载方法* @param fileName 文件名称（PZ_DEMO.zip）* @param filePath 文件路径（D://uploadFiles//PG//IMAGE//176d10329c29420e97fce1a39586a7b220190801091805//YX_zip_20190801091845856.zip）* @param request  * @param response*/public static void filedownShowEX(String fileName, String filePath,HttpServletRequest request, HttpServletResponse response)throws Exception {// 看到response中的usingWriter=true，随即想办法将该标志位设置为false;response.reset(),即可，注意reset后缓存消失，设置消失。response.reset();// 得到该文件File file = new File(filePath);FileInputStream fileInputStream = new FileInputStream(file);// 设置Http响应头告诉浏览器下载这个附件String userAgent = request.getHeader("User-Agent");// 针对IE或者以IE为内核的浏览器：if (userAgent.contains("MSIE") || userAgent.contains("Trident")) {fileName = java.net.URLEncoder.encode(fileName, "UTF-8");} else {// 非IE浏览器的处理：fileName = new String(fileName.getBytes("UTF-8"), "ISO-8859-1");}response.setHeader("Content-disposition",String.format("attachment; filename=\"%s\"", fileName));response.setContentType("application/vnd.ms-excel;charset=utf-8");response.setCharacterEncoding("UTF-8");OutputStream outputStream = response.getOutputStream();byte[] bytes = new byte[2048];int len = 0;while ((len = fileInputStream.read(bytes)) > 0) {outputStream.write(bytes, 0, len);}fileInputStream.close();outputStream.close();}/*** txt文件编码判断* * @param filePath*            文件路径* @return (是：true（是：US-ASCII 编码） ;否:false（不是：US-ASCII 编码） )* @throws Exception*/// java编码 与 txt编码对应// java txt// unicode unicode big endian// utf-8 utf-8// utf-16 unicode// gb2312 ANSIpublic static boolean checkIsFileASCII(String filepath) throws Exception {File sourceFile = new File(filepath);String charset = "GB2312";byte[] first3Bytes = new byte[3];try {boolean checked = false;BufferedInputStream bis = new BufferedInputStream(new FileInputStream(sourceFile));bis.mark(0);int read = bis.read(first3Bytes, 0, 3);if (read == -1) {charset = "GB2312"; // 文件编码为 ANSI} else if (first3Bytes[0] == (byte) 0xFF&& first3Bytes[1] == (byte) 0xFE) {charset = "UTF-16LE"; // 文件编码为 Unicodechecked = true;} else if (first3Bytes[0] == (byte) 0xFE&& first3Bytes[1] == (byte) 0xFF) {charset = "UTF-16BE"; // 文件编码为 Unicode big endianchecked = true;} else if (first3Bytes[0] == (byte) 0xEF&& first3Bytes[1] == (byte) 0xBB&& first3Bytes[2] == (byte) 0xBF) {charset = "UTF-8"; // 文件编码为 UTF-8checked = true;}bis.reset();if (!checked) {int loc = 0;while ((read = bis.read()) != -1) {loc++;if (read >= 0xF0)break;if (0x80 <= read && read <= 0xBF) // 单独出现BF以下的，也算是GBKbreak;if (0xC0 <= read && read <= 0xDF) {read = bis.read();if (0x80 <= read && read <= 0xBF) // 双字节 (0xC0 - 0xDF)// (0x80// - 0xBF),也可能在GB编码内continue;elsebreak;} else if (0xE0 <= read && read <= 0xEF) {// 也有可能出错，但是几率较小read = bis.read();if (0x80 <= read && read <= 0xBF) {read = bis.read();if (0x80 <= read && read <= 0xBF) {charset = "UTF-8";break;} elsebreak;} elsebreak;}}}bis.close();} catch (Exception e) {e.printStackTrace();}System.out.println("文件：" + filepath + "的编码格式为：" + charset);if (charset.equalsIgnoreCase("GB2312")) {return true;} else {return false;}}/*** 创建目录* * @param destDirName目标目录名* @return*/public static Boolean createDir(String destDirName) {File dir = new File(destDirName);if (!dir.getParentFile().exists()) { // 判断有没有父路径，就是判断文件整个路径是否存在return dir.getParentFile().mkdirs(); // 不存在就全部创建}return false;}/*** 删除文件* * @param filePathAndName*            String 文件路径及名称 如c:/fqf.txt* @param fileContent*            String* @return boolean*/public static void delFile(String filePathAndName) {try {String filePath = filePathAndName;filePath = filePath.toString();java.io.File myDelFile = new java.io.File(filePath);myDelFile.delete();} catch (Exception e) {System.out.println("删除文件操作出错");e.printStackTrace();}}/*** 读取到字节数组0* * @param filePath*            //路径* @throws IOException*/public static byte[] getContent(String filePath) throws IOException {File file = new File(filePath);long fileSize = file.length();if (fileSize > Integer.MAX_VALUE) {System.out.println("file too big...");return null;}FileInputStream fi = new FileInputStream(file);byte[] buffer = new byte[(int) fileSize];int offset = 0;int numRead = 0;while (offset < buffer.length&& (numRead = fi.read(buffer, offset, buffer.length - offset)) >= 0) {offset += numRead;}// 确保所有数据均被读取if (offset != buffer.length) {throw new IOException("Could not completely read file "+ file.getName());}fi.close();return buffer;}/*** 读取到字节数组1* * @param filePath* @return* @throws IOException*/public static byte[] toByteArray(String filePath) throws IOException {File f = new File(filePath);if (!f.exists()) {throw new FileNotFoundException(filePath);}ByteArrayOutputStream bos = new ByteArrayOutputStream((int) f.length());BufferedInputStream in = null;try {in = new BufferedInputStream(new FileInputStream(f));int buf_size = 1024;byte[] buffer = new byte[buf_size];int len = 0;while (-1 != (len = in.read(buffer, 0, buf_size))) {bos.write(buffer, 0, len);}return bos.toByteArray();} catch (IOException e) {e.printStackTrace();throw e;} finally {try {in.close();} catch (IOException e) {e.printStackTrace();}bos.close();}}/*** 读取到字节数组2* * @param filePath* @return* @throws IOException*/public static byte[] toByteArray2(String filePath) throws IOException {File f = new File(filePath);if (!f.exists()) {throw new FileNotFoundException(filePath);}FileChannel channel = null;FileInputStream fs = null;try {fs = new FileInputStream(f);channel = fs.getChannel();ByteBuffer byteBuffer = ByteBuffer.allocate((int) channel.size());while ((channel.read(byteBuffer)) > 0) {// do nothing// System.out.println("reading");}return byteBuffer.array();} catch (IOException e) {e.printStackTrace();throw e;} finally {try {channel.close();} catch (IOException e) {e.printStackTrace();}try {fs.close();} catch (IOException e) {e.printStackTrace();}}}/*** Mapped File way MappedByteBuffer 可以在处理大文件时，提升性能* * @param filename* @return* @throws IOException*/public static byte[] toByteArray3(String filePath) throws IOException {FileChannel fc = null;RandomAccessFile rf = null;try {rf = new RandomAccessFile(filePath, "r");fc = rf.getChannel();MappedByteBuffer byteBuffer = fc.map(MapMode.READ_ONLY, 0,fc.size()).load();// System.out.println(byteBuffer.isLoaded());byte[] result = new byte[(int) fc.size()];if (byteBuffer.remaining() > 0) {// System.out.println("remain");byteBuffer.get(result, 0, byteBuffer.remaining());}return result;} catch (IOException e) {e.printStackTrace();throw e;} finally {try {rf.close();fc.close();} catch (IOException e) {e.printStackTrace();}}}/*** 写入文件* * @param filePath* @param content*/public static void contentToTxt(String filePath, String content) {String str = new String(); // 原有txt内容String s1 = new String();// 内容更新try {File f = new File(filePath);if (f.exists()) {System.out.print("文件内容写入时 文件存在");BufferedWriter output = new BufferedWriter(new FileWriter(f));output.write("");output.close();} else {System.out.print("文件内容写入时 文件不存在");f.createNewFile();// 不存在则创建}BufferedWriter output = new BufferedWriter(new FileWriter(f));output.write(content);output.close();} catch (Exception e) {e.printStackTrace();}}// 读取文件总行数public static int readFileLineNums(String filepath, String filename) {int x = 0;// 用于统计行数，从0开始try {FileReader fr = new FileReader(filepath); // 这里定义一个字符流的输入流的节点流，用于读取文件（一个字符一个字符的读取）BufferedReader br = new BufferedReader(fr); // 在定义好的流基础上套接一个处理流，用于更加效率的读取文件（一行一行的读取）while (br.readLine() != null) { // readLine()方法是按行读的，返回值是这行的内容x++; // 每读一行，则变量x累加1}br.close();fr.close();} catch (Exception e) {e.printStackTrace();}return x; // 返回总的行数}
}

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