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[英]Unable to retrive data from database and display in JSP using Servlet
[英]Unable to show images in JSP from database using servlet
我正在尝试使用servlet从mysql数据库中获取和显示,保存为JSP上blob的图像。 我编写的代码引用了许多网站,但仍然无法正常工作。 我没有收到任何类型的错误。 它的显示像这样
我已经使用创建了表格
create table contacts(id int not null auto_increment,
name varchar(40),
second varchar(40),
photo blob,
primary key(id));
这是我的Servlet DisplayServlet.java
@WebServlet("/DisplayServlet")
public class DisplayServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
Connection conn = null;
PreparedStatement stmt = null;
ResultSet rs = null;
public void init() throws ServletException {
}
public DisplayServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String imageId = request.getParameter("id");
System.out.println(imageId);
InputStream sImage;
// Check if ID is supplied to the request.
if (imageId == null) {
// Do your thing if the ID is not supplied to the request.
// Throw an exception, or send 404, or show default/warning image, or just ignore it.
response.sendError(HttpServletResponse.SC_NOT_FOUND); // 404.
return;
}
try{
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/projectbuy", "root","root");
stmt = conn.prepareStatement("select photo from contacts where id=" + imageId);
rs = stmt.executeQuery();
if(rs.next()){
System.out.println("Inside RS");
byte[] bytearray = new byte[1048576];
int size=0;
sImage = rs.getBinaryStream(4);
response.reset();
response.setContentType("image/jpeg");
while((size = sImage.read(bytearray)) != -1 ){
response.getOutputStream().
write(bytearray,0,size);
}
}
} catch (Exception e){
e.printStackTrace();
}
}
}
这是我的jsp页面imagedemo.jsp
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JSP Page</title>
</head>
<body>
<h1>Hello World!</h1>
<img src="DisplayServlet?id=1" height="150px" width="150px" alt="ProfilePic">
</body>
</html>
最后这是我的xml文件
<servlet-mapping>
<servlet-name>action</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>DisplayServlet</servlet-name>
<servlet-class>DisplayServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>DisplayServlet</servlet-name>
<url-pattern>/DisplayServlet/*</url-pattern>
</servlet-mapping>
您仅选择一列:
stmt = conn.prepareStatement("select photo from contacts where id=" + imageId);
但后来尝试检索第4个:
sImage = rs.getBinaryStream(4);
而且在编写循环之后您没有flush()调用。 另外,最好使用池中的连接,而不是直接从driverManager实例化连接,并在工作后将其关闭。
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