ImageTag小案例

其实不使用ImageIO，就是用一般的BufferedOutputStream+byte[] buffer也可以

关键在于通过response设置页面的MIME Type，自行Google~~~

源代码直接帖了。。。

ImageTag.java

public class ImageTag extends SimpleTagSupport {

    private String fileName;
    private HttpServletResponse response;
    private String imageType;
    public void setImageType(String imageType) {
        this.imageType = imageType;
    }
    public void setFileName(String fileName) {
        this.fileName = fileName;
    }
    public void setResponse(HttpServletResponse response) {
        this.response = response;
    }
    @Override
    public void doTag() throws JspException, IOException {
        response.setContentType("image/" + imageType); // This is necessary!!!
        BufferedImage image = null;
        BufferedOutputStream outputStream = null;
        try {
            File imageFile = new File(fileName);
            Image src = ImageIO.read(imageFile);
            int width = src.getWidth(null);
            int height = src.getHeight(null);
            image = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);
            image.getGraphics().drawImage(src, 0, 0, width, height, null);
            outputStream = new BufferedOutputStream(response.getOutputStream());
            ImageIO.write(image, imageType, outputStream);
            outputStream.flush(); // write the content from the buffer to the page
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (outputStream != null)
                outputStream.close();
        }
    }

}

tagext.tld

<?xml version="1.0" encoding="UTF-8"?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
    version="2.0">
    
    <description>Tag extensions, my customized tag library.</description>
    <display-name>xxx ext tags</display-name>
    <tlib-version>1.0</tlib-version>
    <short-name>ext</short-name>
    <uri>http://tags.xxx.com/ext</uri>

    
    <tag>
        <description>
            Load the specified image file and display it on the page.
        </description>
        <name>image</name>
        <tag-class>com.v1.ex120.ImageTag</tag-class>
        <body-content>empty</body-content>
        
        <attribute>
            <description>
                The file extension of the image file.
            </description>
            <name>imageType</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        
        <attribute>
            <description>
                The URI of the image file on the disk.
            </description>
            <name>fileName</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        
        <attribute>
            <description>
                The HttpServletResponse of the display page.
                Normally you'd use the response object of the page
                in which this tag is used.
            </description>
            <name>response</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
    
</taglib>

imagetag.jsp

<%@ page language="java" contentType="text/html; charset=GBK"
    pageEncoding="GBK"%>
<%@ taglib uri="http://tags.xxx.com/ext" prefix="ext" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GBK">
<title>Insert title here</title>
</head>
<body>
    <ext:image response="${pageContext.response }" fileName="D:qq.png" imageType="PNG"/>
</body>
</html>
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原文地址：https://www.cnblogs.com/qrlozte/p/3543917.html