​​​​​​​javax.imageio.IIOException: Can't create output stream!

运行一个注册显示验证码图片的小程序，之前在myeclipse上运行正常，但是今天移动到idea上就报错了，生成的图片显示不出来

javax.imageio.IIOException: Can't create output stream!
	javax.imageio.ImageIO.write(ImageIO.java:1574)
	cn.edu.sicau.utils.VerifyCode.output(VerifyCode.java:104)
	cn.edu.sicau.web.servlet.VerifyCodeServlet.doGet(VerifyCodeServlet.java:27)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

Root Cause

javax.imageio.IIOException: Can't create cache file!
	javax.imageio.ImageIO.createImageOutputStream(ImageIO.java:423)
	javax.imageio.ImageIO.write(ImageIO.java:1572)
	cn.edu.sicau.utils.VerifyCode.output(VerifyCode.java:104)
	cn.edu.sicau.web.servlet.VerifyCodeServlet.doGet(VerifyCodeServlet.java:27)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

Root Cause

java.nio.file.AccessDeniedException: D:\Program Files\apache-tomcat-8.5.23\temp\imageio8710657563592930352.tmp
	sun.nio.fs.WindowsException.translateToIOException(WindowsException.java:83)
	sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:97)
	sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:102)
	sun.nio.fs.WindowsFileSystemProvider.newByteChannel(WindowsFileSystemProvider.java:230)
	java.nio.file.Files.newByteChannel(Files.java:361)
	java.nio.file.Files.createFile(Files.java:632)
	java.nio.file.TempFileHelper.create(TempFileHelper.java:138)
	java.nio.file.TempFileHelper.createTempFile(TempFileHelper.java:161)
	java.nio.file.Files.createTempFile(Files.java:897)
	javax.imageio.stream.FileCacheImageOutputStream.<init>(FileCacheImageOutputStream.java:88)
	com.sun.imageio.spi.OutputStreamImageOutputStreamSpi.createOutputStreamInstance(OutputStreamImageOutputStreamSpi.java:68)
	javax.imageio.ImageIO.createImageOutputStream(ImageIO.java:419)
	javax.imageio.ImageIO.write(ImageIO.java:1572)
	cn.edu.sicau.utils.VerifyCode.output(VerifyCode.java:104)
	cn.edu.sicau.web.servlet.VerifyCodeServlet.doGet(VerifyCodeServlet.java:27)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

参考网上的方法：https://blog.youkuaiyun.com/chenzenan/article/details/5604598

将这句代码ImageIO.write(image, "JPEG", out);
改成下面就可以了：
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
encoder.encode(image);

再次运行就成功了

后来观察

java.nio.file.AccessDeniedException: D:\Program Files\apache-tomcat-8.5.23\temp\imageio8710657563592930352.tmp

这个错误，可能是和权限有关，我在本机win10 系统上把D:\Program Files\apache-tomcat-8.5.23\temp的权限修改称可写入

选中temp文件夹，右键选中属性

添加允许写入或修改权限，就可以。