Servlet从本地文件中读取图片，并显示在页面中

时间 2019-11-08

原文原文链接

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import com.sun.image.codec.jpeg.*;//sun公司仅提供了jpg图片文件的编码api
import javax.imageio.stream.*;
import java.awt.*;
import java.awt.image.BufferedImage;

/**
 * 
 * 显示文件的Servlet
 * 负责从本地文件中读取图片，
 * 
 */
public class ShowPic extends javax.servlet.http.HttpServlet implements
        javax.servlet.Servlet {

    private static final String GIF = "image/gif;charset=GB2312";// 设定输出的类型

    private static final String JPG = "image/jpeg;charset=GB2312";

    /*
     * (non-Java-doc)
     * 
     * @see javax.servlet.http.HttpServlet#HttpServlet()
     */
    public ShowPic() {
        super();
    }

    /*
     * (non-Java-doc)
     * 
     * @see javax.servlet.http.HttpServlet#doGet(HttpServletRequest request,
     *      HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }

    /*
     * (non-Java-doc)
     * 
     * @see javax.servlet.http.HttpServlet#doPost(HttpServletRequest request,
     *      HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        String spec = request.getParameter("spec");// 输出图片的类型的标志

        String imagePath = "D:\\temp\\1.jpg";

        response.reset();

        OutputStream output = response.getOutputStream();// 获得输出流
        if (imagePath.toLowerCase().endsWith(".jpg"))// 使用编码处理文件流的状况：
        {
            response.setContentType(JPG);// 设定输出的类型
            // 获得图片的真实路径

            // 获得图片的文件流
            InputStream imageIn = new FileInputStream(new File(imagePath));
            // 获得输入的编码器，将文件流进行jpg格式编码
            JPEGImageDecoder decoder = JPEGCodec.createJPEGDecoder(imageIn);
            // 获得编码后的图片对象
            BufferedImage image = decoder.decodeAsBufferedImage();
            // 获得输出的编码器
            JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(output);
            encoder.encode(image);// 对图片进行输出编码
            imageIn.close();// 关闭文件流
        }
        if (imagePath.toLowerCase().endsWith(".gif"))// 不使用编码处理文件流的状况：
        {
            response.setContentType(GIF);
            ServletContext context = getServletContext();// 获得背景对象
            InputStream imageIn = context.getResourceAsStream(imagePath);// 文件流
            BufferedInputStream bis = new BufferedInputStream(imageIn);// 输入缓冲流
            BufferedOutputStream bos = new BufferedOutputStream(output);// 输出缓冲流
            byte data[] = new byte[4096];// 缓冲字节数
            int size = 0;
            size = bis.read(data);
            while (size != -1) {
                bos.write(data, 0, size);
                size = bis.read(data);
            }
            bis.close();
            bos.flush();// 清空输出缓冲流
            bos.close();
        }
        output.close();
    }
}

想要调用的话，你能够简单的映射一下servelt，我就将servet的名映射为html

<servlet>
      <servlet-name>ShowPic</servlet-name>
      <display-name>ShowPic</display-name>
      <description></description>
      <servlet-class>
      cn.ccb.zlgz.web.servlet.ShowPic</servlet-class>
  </servlet>
  <servlet-mapping>
      <servlet-name>ShowPic</servlet-name>
      <url-pattern>/ShowPic</url-pattern>
  </servlet-mapping>

使用HTML调用：java

<html>
<body>
<img src="ShowPic?spec=2"></a>
</body>
</html>

这样图片便显示在htm上了web

转载于：http://tntxia.iteye.com/blog/826193

JSP中显示图片的主要代码就是:api

　　<img src="http://localhost:8080/imgShow/ImageShowServlet" />app

　　其中"imgShow"是项目名称, "ImageShowServlet"是url-pattern.编码