java.lang.IllegalStateException: getWriter() has already been called for this response問題解決
在做圖檔驗證碼的是後遇到這個問題！
異常産生原因：web容器生成的servlet代碼中有out.write(""),這個和JSP中調用的response.getOutputStream()産生沖突.即Servlet規範說明，不能既調用response.getOutputStream()，又調用response.getWriter()，無論先調用哪一個，在調用第二個時候應會抛出IllegalStateException，因為在jsp中，out變量實際上是通過response.getWriter得到的，你的程式中既用了 response.getOutputStream，又用了out變量，故出現以上錯誤。
解決：添加一個語句
response.reset();
圖檔校驗碼學習代碼：（eclipse 環境測試）
參考（轉自）：https://www.cnblogs.com/h--d/p/8258610.html
- 生成校驗碼的工具類：
package com.kk.utils;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.Random;
import javax.imageio.ImageIO;
public class VerifyCodeUtils {
//使用到Algerian字型，系統裡沒有的話需要安裝字型，字型隻顯示大寫，去掉了1,0,i,o幾個容易混淆的字元
public static final String VERIFY_CODE = "23456789ABCDEFGHIJKLMNPQRSTUVWXYZ";
private static Random random = new Random();
//使用系統預設字元源生成驗證碼
//verifySize: 驗證碼長度
public static String generateVerifyCode(int verifySize) {
return generateVerifyCode(verifySize,VERIFY_CODE);
}
private static String generateVerifyCode(int verifySize, String verifyCode) {
if(verifyCode == null || verifyCode.length() == 0) {
verifyCode = VERIFY_CODE;
}
int codesLen = verifyCode.length();
Random random = new Random(System.currentTimeMillis());
StringBuilder verifyCode1 = new StringBuilder(verifySize);
for(int i= 0;i<verifySize;i++) {
verifyCode1.append(verifyCode.charAt(random.nextInt(codesLen-1)));
}
return verifyCode1.toString();
}
public static String outputVerifyImage(int w,int h,File outputFile,int verifySize)throws IOException {
String verifyCode = generateVerifyCode(verifySize);
outputImage(w,h,outputFile,verifyCode);
return verifyCode;
}
public static String outputVerifyImage(int w,int h,OutputStream os,int verifySize)throws IOException {
String verifyCode = generateVerifyCode(verifySize);
outputImage(w, h, os, verifyCode);
return verifyCode;
}
public static void outputImage(int w, int h, File outputFile, String verifyCode) throws IOException {
// TODO Auto-generated method stub
if(outputFile == null) {
return;
}
File dir = outputFile.getParentFile();
if(dir.exists()) {
dir.mkdirs();
}
try {
outputFile.createNewFile();
FileOutputStream fos = new FileOutputStream(outputFile);
outputImage(w, h, fos, verifyCode);
fos.close();
} catch (IOException e) {
throw e;
}
}
public static void outputImage(int w, int h, OutputStream os, String code) throws IOException {
// TODO Auto-generated method stub
int verifySize = code.length();
BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
Random rand = new Random();
Graphics2D g2 = image.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING
, RenderingHints.VALUE_ANTIALIAS_ON);
Color[] colors = new Color[5];
Color[] colorSpaces = new Color[] {Color.WHITE, Color.CYAN,
Color.GRAY, Color.LIGHT_GRAY, Color.MAGENTA, Color.ORANGE,
Color.PINK, Color.YELLOW };
float[] fractions = new float[colors.length];
for(int i=0;i<colors.length;i++) {
colors[i] = colorSpaces[rand.nextInt(colorSpaces.length)];
fractions[i] = rand.nextFloat();
}
Arrays.sort(fractions);
g2.setColor(Color.DARK_GRAY); //設定邊框
g2.fillRect(0, 0, w, h);
Color c = getRandColor(200,250);
g2.setColor(c); //設定背景顔色
g2.fillRect(0, 2, w, h-4);
//繪制幹擾線條
Random random = new Random();
g2.setColor(getRandColor(160, 200));
for(int i=0;i<20;i++) {
int x = random.nextInt(w-1);
int y = random.nextInt(h-1);
int x1 = random.nextInt(6)+1;
int y1 = random.nextInt(12)+1;
g2.drawLine(x, y, x+x1+40, y+y1+20);
}
// // 添加噪點
float yawpRate = 0.0f; //噪聲率
int area = (int) (yawpRate*w*h);
for(int i=0;i<area;i++) {
int x = random.nextInt(w);
int y = random.nextInt(h);
int rgb = getRandomIntColor();
image.setRGB(x, y, rgb);
}
shear(g2, w, h, c);// 使圖檔扭曲
g2.setColor(getRandColor(100, 160));
int fontSize = h-4;
Font font = new Font("Algerian", Font.ITALIC,fontSize);
g2.setFont(font);
char[] chars = code.toCharArray();
for(int i = 0; i < verifySize; i++) {
AffineTransform affine = new AffineTransform();
affine.setToRotation(Math.PI/4*rand.nextDouble()* (rand.nextBoolean() ? 1 : -1), (w / verifySize) * i + fontSize/2, h/2);
g2.setTransform(affine);
g2.drawChars(chars, i,1, ((w-10) / verifySize) * i + 5, h/2 + fontSize/2 - 10);
}
g2.dispose();
ImageIO.write(image, "PNG", os);
}
private static Color getRandColor(int fc, int bc) {
// TODO Auto-generated method stub
if(fc>255) {
fc = 255;
}
if(bc > 255) {
bc = 255;
}
int r = fc + random.nextInt(bc - fc);
int g = fc + random.nextInt(bc - fc);
int b= fc + random.nextInt(bc - fc);
return new Color(r,g,b);
}
private static int getRandomIntColor() {
int[] rgb = getRandomRgb();
int color = 0;
for(int c: rgb) {
color = color <<8;
color = color | c;
}
return color;
}
private static int[] getRandomRgb(){
int[] rgb = new int[3];
for(int i =0;i<3;i++) {
rgb[i] = random.nextInt(255);
}
return rgb;
}
private static void shear(Graphics g, int w1, int h1, Color color) {
shearX(g, w1, h1, color);
shearY(g, w1, h1, color);
}
private static void shearX(Graphics g, int w1, int h1, Color color) {
// TODO Auto-generated method stub
int period = random.nextInt(2);
boolean borderGap = true;
int frames = 1;
int phase = random.nextInt(2);
for(int i = 0;i < h1; i++) {
double d = (double) (period >>1)
* Math.asin((double) i / (double)period
+(6.2831853071795862D * (double) phase)
/ (double) frames);
g.copyArea(0, i, w1, 1, (int)d, 0);
if(borderGap) {
g.setColor(color);
g.drawLine((int)d, i, 0,i);
g.drawLine((int)d+w1,i , w1, i);
}
}
}
private static void shearY(Graphics g, int w1, int h1, Color color) {
// TODO Auto-generated method stub
int period = random.nextInt(40) + 10;
boolean borderGap = true;
int frames = 20;
int phase = 7;
for(int i = 0;i<w1;i++) {
double d = (double) (period >> 1)
* Math.sin((double) i / (double) period
+ (6.2831853071795862D * (double) phase)
/ (double) frames);
g.copyArea(i, 0, 1, h1, 0, (int) d);
if (borderGap) {
g.setColor(color);
g.drawLine(i, (int) d, i, 0);
g.drawLine(i, (int) d + h1, i, h1);
}
}
}
public static void main(String[] args) throws IOException{
File dir = new File("G:/圖形校驗碼/");
int w = 200, h = 80;
String verifyCode = generateVerifyCode(4);
File file = new File(dir, verifyCode + ".jpg");
outputImage(w, h, file, verifyCode);
System.out.println("圖形校驗碼生成成功");
}
}
- 産生驗證碼servlet的源碼：
package com.kk.code;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.kk.utils.VerifyCodeUtils;
@WebServlet("/CreateCodeServlet")
public class CreateCodeServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public CreateCodeServlet() {
super();
// TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
//response.getWriter().append("Served at: ").append(request.getContextPath());
response.setContentType("text/html; charset=UTF-8");
PrintWriter out = response.getWriter();
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
response.setContentType("image/jpeg");
//生成随機字串
String verifyCode = VerifyCodeUtils.generateVerifyCode(4);
out.print(verifyCode);
//存入會話session
request.getSession().setAttribute("CODE", verifyCode.toLowerCase());
//生成圖檔
int width = 100;//寬
int height = 40;//高
response.reset();
VerifyCodeUtils.outputImage(width, height, response.getOutputStream(), verifyCode);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
- 校驗前端輸入的驗證碼的servlet源碼：
package com.kk.code;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/VerifyCodeServlet")
public class VerifyCodeServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public VerifyCodeServlet() {
super();
// TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.getWriter().append("Served at: ").append(request.getContextPath());
response.setContentType("text/html; charset=UTF-8");
PrintWriter out = response.getWriter();
String code = request.getParameter("code");
out.println("code="+code);
String key = (String) request.getSession().getAttribute("CODE");
if(code != null && code.equalsIgnoreCase(key)){
request.getSession().removeAttribute("CODE");
response.getWriter().println(true);
}else{
response.getWriter().println(false);
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
- 前端頁面jsp源碼：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'ImageCode.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<h2>測試驗證碼：</h2>
請輸入驗證碼：<input type="text" name="code" /><img id="codeimg"
src="${pageContext.request.contextPath }/CreateCodeServlet"
onclick="changeImg()"><a href="javascript:void(0);" onclick="changeImg()">
看不清，換一張</a>
<button onclick="submit()">送出</button>
<script type="text/javascript">
//改變驗證碼事件
function changeImg(){
alert("nihao");
var img = document.getElementById('codeimg');
img.src = "${pageContext.request.contextPath }/CreateCodeServlet?x=" + Math.floor(Math.random()*100)
}
//送出驗證并驗證驗證碼
function submit(){
var input = document.getElementsByTagName('input')[0];
var val = input.valueOf();
alert("input="+input.value);
//ajax送出
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function(){
if(xhr.readyState == 4 && xhr.status == 200) {
alert(xhr.responseText);
}
}
xhr.open('get','${pageContext.request.contextPath }/VerifyCodeServlet?code=' + input.value);
xhr.send(null);
}
</script>
</body>
</html>
- 結果截圖：
-
java.lang.IllegalStateException: getWriter() has already been called for this response問題解決和java圖形驗證碼java.lang.IllegalStateException: getWriter() has already been called for this response問題解決