将 blob 图像从数据库显示到 jlabel答案

【问题标题】：Display blob image from database into jlabel将 blob 图像从数据库显示到 jlabel
【发布时间】：2013-11-29 06:18:12
【问题描述】：

public void displayPhoto() {

    rs = null;
    String displaySQL = "select * from images where USERNAME ='" + temp.getUsername() + "'";
    try {

        con = getDBConnection();
        rs = st.executeQuery(displaySQL);
        while (rs.next()) {
            BufferedImage im = ImageIO.read(rs.getBinaryStream("IMAGES"));
            displayPhoto.setIcon(new ImageIcon(im));
        }

    } catch (Exception e) {
        e.printStackTrace();
    }


}

我正在尝试显示来自数据库的图像，该图像存储为 longblob。它说 NULLPOINTERS，我不知道是什么问题

该表有 2 列(USERNAME,IMAGES)
图片 = 表名，
IMAGES = 列名，
displayPhoto = JLabel

谁能帮助我？提前感谢

这是完整的错误信息

java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(ImageIcon.java:228)
at MyProfile.displayPhoto(MyProfile.java:395)
at MyProfile.<init>(MyProfile.java:195)
at Login.actionPerformed(Login.java:93)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:729)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:688)
at java.awt.EventQueue$3.run(EventQueue.java:686)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:702)
at java.awt.EventQueue$4.run(EventQueue.java:700)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:699)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

【问题讨论】：

您能否详细说明哪一部分给您NullPointerException？是 ImageIO.read 吗？
您的IMAGES 列是否定义为not null？否则，您应该在尝试读取之前测试null。此外，您应该在尝试显示之前测试im 不是null，因为ImageIO 不能神奇地将任何类型的blob 变成BufferedImage。
我编辑了帖子，我包含了错误消息。定义为不为空的 IMAGES 列，则数据类型为 longblob
你想解决什么问题？ NullPoniterException 走开，或者理解为什么 ImageIO 不能读取你的 blob 中的数据？第一个是微不足道的，不适合 SO。第二个需要您提供更多输入（即，当您遇到 NPE 时，您的 blob 的内容是什么？）。
如何读取我的blob中的数据（图像）并将其显示到jlabel中

标签： java mysql blob bufferedimage javax.imageio

【解决方案1】：

   try {
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/login", "root", "obierofelix");
            stmt = con.createStatement();
            rs = stmt.executeQuery("select * from images");
            rs.next();
            BufferedImage im = ImageIO.read(rs.getBinaryStream("Image"));
            BackGroundImage.setIcon(new ImageIcon(im));
        } catch (Exception err) {
            JOptionPane.showMessageDialog(this, err.getMessage());
        }

【讨论】：

【解决方案2】：

应用 rs.next();在 try and catch 块之前将指针移动到数据库中的第一条记录。

【讨论】：