Spring Boot整合模板引擎freemarker以及servlet

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=false
spring.freemarker.cache=false
spring.freemarker.check-template-location=true
spring.freemarker.charset=UTF-8
spring.freemarker.content-type=text/html
spring.freemarker.expose-request-attributes=false
spring.freemarker.expose-session-attributes=false
spring.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;

@Controller
public 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
@ServletComponentScan
public 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