从数据库读出的JPG文件的字符流，转换成图片显示在页面上的相关代码

最新推荐文章于 2022-05-08 22:37:37 发布

转载最新推荐文章于 2022-05-08 22:37:37 发布 · 1k 阅读

文章标签：

#数据库 #exception #sql #null #byte #image

本文介绍如何使用Java从数据库中读取图片，并将其直接显示在网页上或保存为文件。通过设置HTTP响应类型为图像格式，可以将查询结果中的二进制流转换为图像输出。

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public void doPost(HttpServletRequest req, HttpServletResponse res)
    throws ServletException, IOException {
    ServletOutputStream out = res.getOutputStream();
    Statement dispStmt = null, setStmt = null;
    try {
        dispStmt = Con.createStatement();
        setStmt = Con.createStatement();
        setStmt.executeUpdate("set textsize 2048000");
    } catch (Exception e) {
        out.println("Create Statement error:" + e.toString() + "<br>");
    }

    String ls_sql = null;
    ls_sql = req.getParameter("ImageSQL");
    if (ls_sql == null)
        ls_sql = "";
    ls_sql = ls_sql.trim();
    if (!ls_sql.equals("")) {
        ResultSet rs = null;
        try {
            rs = dispStmt.executeQuery(ls_sql);
        } catch (Exception e) {
            System.out.println(
                "Unable to Exec Statment" + e.toString() + "<br>");
        }
        try {
            while (rs.next()) {
                try {
                    res.setContentType("image/jpeg");
                    InputStream is = rs.getBinaryStream(1);
                    int size = is.available();
                    byte[] bzp = new byte[size];
                    is.read(bzp);
                    out.write(bzp);
                } catch (Exception e) {
                    System.out.println("Wirte image error: " + e.toString());
                }
            }
            rs.close();
        } catch (Exception e) {
            System.out.println("Unable to Close Statment" + e.toString());
        }
    }
    try {
        dispStmt.close();
    } catch (Exception e) {
        System.out.println("Close Statement Error: " + e.toString());
    }
    out.close();
}

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再附一个：

从库中读图片显示到页面上的主要源码
<%@ page contentType="text/html;charset=iso8859_1"%>
<%@ page import="java.sql.ResultSet"%>
<jsp:useBean id="query" class="pub.MakeDB"/>
<%
String sql = "select * from images";
ResultSet rs = query.executeQuery(sql);
rs.next();
InputStream in = rs.getBinaryStream("image");
ServletOutputStream sos = response.getOutputStream();
int len = 0;
byte[] b = new byte[1024];
response.reset();
response.setContentType("image/gif");
while((len = in.read(b)) > 0)
sos.write(b,0,len);
in.close();
sos.close();
query.cls();
%>
如果是写到文件只要把sos
定义为DataOutputStream sos = new DataOutputStream(new BufferedOutputStream(new FileOutputStream("/a.gif")));