实现P数据库图片预览功能 (jsp从数据库读取图片预览功能的实现)
P（JavaServer Pages）作为一种动态网页开发技术，广泛应用于网页开发领域。同时，更多的网页应用需要对图片进行管理和展示，这时候就需要实现数据库图片预览功能，以便更好地展示网页内容和产品。
一、P数据库图片上传
在之前，我们需要先实现P数据库图片上传功能。这里我们以MySQL数据库为例，通过P上传图片并将图片保存到数据库中。
1、创建P页面
在P页面中添加文件上传表单，并将表单提交到一个名为upload.jsp的文件中。
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2、创建JavaBean
创建一个名为UploadBean的JavaBean，实现图片上传功能。具体实现代码如下：
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public class UploadBean {
private Connection conn;
private PreparedStatement pstmt;
private InputStream inputStream;
public boolean upload(String path, String filename, String contentType, int size) {
try {
conn = ConnectionPool.getConnection();
pstmt = conn.prepareStatement(“insert into images(imageName, imageType, imageSize, imageData) values(?, ?, ?, ?)”);
pstmt.setString(1, filename);
pstmt.setString(2, contentType);
pstmt.setInt(3, size);
pstmt.setBinaryStream(4, inputStream, size);
pstmt.executeUpdate();
return true;
} catch (Exception ex) {
ex.printStackTrace();
return false;
} finally {
ConnectionPool.close(pstmt);
ConnectionPool.close(conn);
}
}
public void setInput(InputStream inputStream) {
this.inputStream = inputStream;
}
}
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3、创建上传Servlet
创建一个名为UploadServlet的Servlet，用于处理文件上传请求。具体实现代码如下：
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public class UploadServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String path = request.getServletContext().getRealPath(“/image”);
String filename = request.getParameter(“filename”);
String contentType = request.getContentType();
int size = request.getContentLength();
InputStream inputStream = request.getInputStream();
UploadBean uploadBean = new UploadBean();
uploadBean.setInput(inputStream);
if(uploadBean.upload(path, filename, contentType, size)) {
response.setContentType(“text/html”);
PrintWriter out = response.getWriter();
out.println(“
文件上传成功
“);
} else {
response.setContentType(“text/html”);
PrintWriter out = response.getWriter();
out.println(“
文件上传失败
“);
}
}
}
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二、P数据库图片预览
在之前，我们需要先实现P数据库图片读取功能。这里我们以MySQL数据库为例，通过P从数据库中读取图片并展示在网页上。
1、创建P页面
在P页面中添加图片展示区域，并读取数据库中的图片数据。
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<%
Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
InputStream inputStream = null;
try {
conn = ConnectionPool.getConnection();
pstmt = conn.prepareStatement(“select * from images where imageName=?”);
pstmt.setString(1, “test.jpg”);
rs = pstmt.executeQuery();
if(rs.next()) {
response.setContentType(rs.getString(“imageType”));
inputStream = rs.getBinaryStream(“imageData”);
int bytesRead = 0;
byte[] buffer = new byte[1024];
OutputStream outputStream = response.getOutputStream();
while ((bytesRead = inputStream.read(buffer, 0, 1024)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
outputStream.flush();
outputStream.close();
}
} catch (Exception ex) {
ex.printStackTrace();
} finally {
ConnectionPool.close(rs);
ConnectionPool.close(pstmt);
ConnectionPool.close(conn);
}
%>
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2、创建显示Servlet
创建一个名为ShowServlet的Servlet，用于显示图片数据。具体实现代码如下：
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public class ShowServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String imageName = request.getParameter(“imageName”);
Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
InputStream inputStream = null;
try {
conn = ConnectionPool.getConnection();
pstmt = conn.prepareStatement(“select * from images where imageName=?”);
pstmt.setString(1, imageName);
rs = pstmt.executeQuery();
if(rs.next()) {
response.setContentType(rs.getString(“imageType”));
inputStream = rs.getBinaryStream(“imageData”);
int bytesRead = 0;
byte[] buffer = new byte[1024];
OutputStream outputStream = response.getOutputStream();
while ((bytesRead = inputStream.read(buffer, 0, 1024)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
outputStream.flush();
outputStream.close();
}
} catch (Exception ex) {
ex.printStackTrace();
} finally {
ConnectionPool.close(rs);
ConnectionPool.close(pstmt);
ConnectionPool.close(conn);
}
}
}
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3、创建P页面
在P页面中添加图片预览区域，并调用ShowServlet来展示图片数据。
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：
通过本文我们了解了如何。具体实现过程包括P数据库图片上传和P数据库图片预览两个步骤。通过以上步骤，我们可以实现对图片数据的上传、读取和展示，为网页开发提供更加丰富、多样化的展示方式。
