java实现保存文件图片以及读取

// 文件转换为字节数组
private byte[] getByteFromFile(File file) {
byte[] be = null;
try {
if (file == null) {
return null;
}
FileInputStream in = new FileInputStream(file);
ByteArrayOutputStream out = new ByteArrayOutputStream(4000);
byte[] b = new byte[4000];
int n;
while ((n = in.read(b)) != -1) {
out.write(b, 0, n);
}
in.close();
out.close();
be = out.toByteArray();
} catch (Exception e) {
e.printStackTrace();
}
return be;
}

// 查看文件
public String execute() throws IOException, DocumentException {
HttpServletResponse response = ServletActionContext.getResponse();
// 清缓存
response.setDateHeader("Expires", 0);
response.setHeader("Pragma", "no-cache");
response.setHeader("Cache-Control", "no-cache");
response.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
// 通过ID获取对象
WorkFlow wf = ws.findById(wfId);
byte[] defs = wf.getProcessFile();
System.out.println(defs);
String wfString = new SAXReader().read(new ByteArrayInputStream(defs))
.asXML();
out.print(wfString);
out.close();
return null;
}

// 查看图片
public String showImg() {
HttpServletResponse response = ServletActionContext.getResponse();
WorkFlow wf = ws.findById(wfId);
try {
response.getOutputStream().write(wf.getProcessImg());
// 清理response
response.flushBuffer();
} catch (Exception e) {
e.printStackTrace();
}
return "showImg";
}