Spring Boot整合模板引擎freemarker以及servlet

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上回分享了第一个spring boot程序之后，相信大家对spring boot已经有了初步的认识，这次分享下在springboot中使用servlet和模板引擎freemarker

一依赖的引入

 <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-freemarker</artifactId>  </dependency>

二编写配置文件application.properties

spring.freemarker.allow-request-override=falsespring.freemarker.cache=falsespring.freemarker.check-template-location=truespring.freemarker.charset=UTF-8spring.freemarker.content-type=text/htmlspring.freemarker.expose-request-attributes=falsespring.freemarker.expose-session-attributes=falsespring.freemarker.expose-spring-macro-helpers=false#spring.freemarker.prefix=#spring.freemarker.request-context-attribute=#spring.freemarker.settings.*=#spring.freemarker.suffix=.ftl#spring.freemarker.template-loader-path=classpath:/templates/ #comma-separated list#spring.freemarker.view-names= # whitelist of view names that can be resolved

默认情况下springboot会去src/main/resources/templates下面找模板页面文件，也可以根据需要进行修改

三编写测试用的controller和模板文件

package com.debug;import java.util.ArrayList;import java.util.Date;import java.util.List;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;@Controllerpublic class FMController {       @RequestMapping("/useFm")   public String  useFm(HttpServletRequest req,HttpServletResponse res) {     String name=req.getParameter("name");    req.setAttribute("name", name);     return "/useFm";   }}

<!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=UTF-8">  <title>fm测试</title></head><body >  <div id="fixed_body">             ${name}  </div></body> </html>

运行效果如下：

spring boot也提供了一个自己的模板引擎，因为我开发使用freemarker较多所以就用它来写例子，大家可以选择其他的如velocity等

四在springboot中使用servlet

有时可能由于历史遗留问题老项目中存在很多servlet如验证码、文件上传等,重新写费时费力，这种情况下就可以保留原先的，使用注解就可以解决

1 改装之前的servlet

package com.debug.servlet;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.ByteArrayOutputStream;import java.io.IOException;import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;@WebServlet(urlPatterns="/imageCode.do",name="ImageCodeServlet")public class ImageCodeServlet extends HttpServlet{private static final long serialVersionUID = 1L;private static int WIDTH = 100;    private static int HEIGHT = 44;    public char[] generateCheckCode() {        // 定义验证码的字符表        String chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";        char[] rands = new char[4];        for (int i = 0; i < 4; i++) {            int rand = (int) (Math.random() * 36);            rands[i] = chars.charAt(rand);        }        return rands;    }    public void drawRands(Graphics g, char[] rands) {        g.setColor(Color.DARK_GRAY);        g.setFont(new Font(null, Font.ITALIC | Font.BOLD, 25));        // 在不同的高度上输出验证码的每个字符        g.drawString("" + rands[0], 1, 30);        g.drawString("" + rands[1], 25, 35);        g.drawString("" + rands[2], 45, 29);        g.drawString("" + rands[3], 65, 25);    }    public void drawBackground(Graphics g) {        // 画背景        g.setColor(new Color(0xDCDCDC));        g.fillRect(0, 0, WIDTH, HEIGHT);        // 随机产生120个干扰点        for (int i = 0; i < 120; i++) {            int x = (int) (Math.random() * WIDTH);            int y = (int) (Math.random() * HEIGHT);            int red = (int) (Math.random() * 255);            int green = (int) (Math.random() * 255);            int blue = (int) (Math.random() * 255);            g.setColor(new Color(red, green, blue));            g.drawOval(x, y, 1, 0);        }    }    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        HttpSession session = request.getSession();        response.setContentType("image/jpeg");        ServletOutputStream sos = response.getOutputStream();        // 设置浏览器不缓存此图片        response.setHeader("Pragma", "No-cache");        response.setHeader("Cache-Control", "no-cache");        response.setDateHeader("Expires", 0);        // 创建内存图像并获得其图形上下文        BufferedImage image = new BufferedImage(WIDTH, HEIGHT,                BufferedImage.TYPE_INT_RGB);        Graphics g = image.getGraphics();        // 产生随机的验证码        char[] rands = generateCheckCode();        // 产生图像        drawBackground(g);        drawRands(g, rands);        // 结束图像的绘制过程,完成图像        g.dispose();        // 将图像输出到客户端        ByteArrayOutputStream bos = new ByteArrayOutputStream();        ImageIO.write(image, "JPEG", bos);        byte[] buf = bos.toByteArray();        response.setContentLength(buf.length);        sos.write(buf);        bos.close();        sos.close();        // 将当前验证码存入到session中        session.setAttribute("checkCode", new String(rands));    }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    }}

就使用注解@WebServlet就行，区别不是很大

2 注册servlet

在App.java加注解@ServletComponentScan即可，如下所示

package com.debug;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.web.servlet.ServletComponentScan;/** * Hello world! * */@SpringBootApplication@ServletComponentScanpublic class App {    public static void main( String[] args )    {        System.out.println( "Hello World!" );        SpringApplication.run(App.class, args);    }}

在浏览器输入servlet的地址看下效果：

下回打算接着分享spring boot整合mybatis，初学者博客可能写的不好，随意看看有问题写评论给我

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