SpringBoot 之 PDF大文件分片加载（后端）

旧城等待， 2023-10-10 13:24 6阅读 0赞

业务需求：前端集成pdf.js 实现在线阅读pdf 文件，但pdf 文件过大时（大于100M）会出现浏览器内存溢出导出程序崩溃的场景发生。针对这个情况，后端给出的解决方案是：分片加载pdf 文件流。

约定:与前端约定在header 头部参数中追加rang 参数：表示需要加载文件片数，后台动态计算起始字节位置，流式输出指定文件内容。

SpringBoot源码：

pom.xml:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    	<modelVersion>4.0.0</modelVersion>
    	<groupId>com.single</groupId>
    	<artifactId>Single</artifactId>
    	<version>0.0.1-SNAPSHOT</version>
    
    	<parent>
    		<groupId>org.springframework.boot</groupId>
    		<artifactId>spring-boot-starter-parent</artifactId>
    		<version>2.1.9.RELEASE</version>
    		<relativePath /> 
    	</parent>
    
    	<properties>
    		<java.version>1.8</java.version>
    		<maven-jar-plugin.version>3.1.1</maven-jar-plugin.version>
    	</properties>
    
    	<dependencies>
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-web</artifactId>
    		</dependency>
    
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-test</artifactId>
    			<scope>test</scope>
    		</dependency>
    	</dependencies>
    
    	<build>
    		<plugins>
    			<plugin>
    				<groupId>org.springframework.boot</groupId>
    				<artifactId>spring-boot-maven-plugin</artifactId>
    			</plugin>
    		</plugins>
    	</build>
    
    
    </project>

application 程序启动窗口

package com.single;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    
    @SpringBootApplication
    public class SingleApplication {
    
    	public static void main(String[] args) {
    		// TODO Auto-generated method stub
    		SpringApplication.run(SingleApplication.class, args);
    	}
    
    }

Controller

package com.single.controller;
    
    import java.io.BufferedInputStream;
    import java.io.BufferedOutputStream;
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.OutputStream;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.stereotype.Controller;
    import org.springframework.util.StringUtils;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    
    /**
     * 
     * @ClassName: FileController
     * @Description: 大文件下載
     * @author: zzg
     */
    
    @Controller
    @RequestMapping("/api/file")
    public class FileController {
    	public static final Logger logger = LoggerFactory.getLogger(FileController.class);
    
    	/**
    	 * 下载文件
    	 * 
    	 * @param identNo
    	 *            文件唯一识别码(经URLEncoder编码)
    	 * @param res
    	 */
    	@RequestMapping(value = "/showpdf", method = RequestMethod.GET)
    	public void showpdf(HttpServletRequest req, HttpServletResponse res) {
    		try {
    			this.download(req, res);
    		} catch (Exception e) {
    			// e.printStackTrace();
    			logger.error("错误信息:{}", e.getMessage(), e);
    		}
    	}
    
    	/**
    	 * 下载文件
    	 * 
    	 * @param identNo
    	 *            文件存储路径(经base64加密和URLEncoder编码)
    	 * @param res
    	 * @throws IOException 
    	 */
    
    	public void download(HttpServletRequest request, HttpServletResponse response) throws IOException {
    		// 从文件存储服务器下载文件到本地
    		File file = new File("D:/test.pdf");
    		BufferedInputStream bis = null;
    		OutputStream os = null;
    		BufferedOutputStream bos = null;
    		InputStream is = null;
    		try {
    			is = new FileInputStream(file);
    			bis = new BufferedInputStream(is);
    			os = response.getOutputStream();
    			bos = new BufferedOutputStream(os);
    			// 下载的字节范围
    			int startByte, endByte, totalByte;
    			if (request != null && request.getHeader("range") != null) {
    				// 起始字节大小
    				String[] range = request.getHeader("range").replaceAll("[^0-9\\-]", "").split("-");
    				// 文件总大小
    				totalByte = is.available();
    				 // 下载起始位置
                    startByte = Integer.parseInt(range[0]);
                    // 下载结束位置
                    if (range.length > 1) {
                        endByte = Integer.parseInt(range[1]);
                    } else {
                        endByte = totalByte - 1;
                    }
    
    				
    				// 返回http状态
    				response.setStatus(206);
    			} else {
    				// 正常下载
    				// 文件总大小
    				totalByte = is.available();
    
    				// 下载起始位置
    				startByte = 0;
    				// 下载结束位置
    				endByte = totalByte - 1;
    				// 返回http状态
    				response.setHeader("Accept-Ranges", "bytes");
    				response.setStatus(206);
    			}
    			// 需要下载字节数
    			int length = endByte - startByte;
    			// 响应头
    			response.setHeader("Accept-Ranges", "bytes");
    			response.setHeader("Content-Range", "bytes " + startByte + "-" + endByte + "/" + totalByte);
    			response.setContentType("Content-Type: application/octet-stream");
    			response.setContentLength(length);
    			// 响应内容
    			bis.skip(startByte);
    			int len = 0;
    			byte[] buff = new byte[1024 * 64];
    			while ((len = bis.read(buff, 0, buff.length)) != -1) {
    				if (length <= len) {
    					bos.write(buff, 0, length);
    					break;
    				} else {
    					length -= len;
    					bos.write(buff, 0, len);
    				}
    			}
    		} catch (IOException e) {
    			System.out.println("下载中断!");
    			logger.error("错误信息:{}", e.getMessage(), e);
    		} finally {
    			bos.close();
    			os.close();
    			bis.close();
    			is.close();
    		}
    
    	}
    
    }

Filter

package com.single.filter;
    
    import java.io.IOException;
    
    import javax.servlet.Filter;
    import javax.servlet.FilterChain;
    import javax.servlet.FilterConfig;
    import javax.servlet.ServletException;
    import javax.servlet.ServletRequest;
    import javax.servlet.ServletResponse;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.stereotype.Component;
    
    /**
     * 
     * @ClassName:  CorsFilter   
     * @Description: SpringBoot 跨域处理拦截器
     * @author: 世纪伟图 -zzg
     * @date:   2021年11月1日 下午3:06:38   
     *     
     * @Copyright: 2021 www.digipower.cn
     */
    
    @Component
    public class CROSFilter implements Filter {
    	public static final Logger logger = LoggerFactory.getLogger(CROSFilter.class);
    	
    	@Override
    	public void init(FilterConfig filterConfig) throws ServletException {
    		// TODO Auto-generated method stub
    		
    	}
    
    	@Override
    	public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
    			throws IOException, ServletException {
    		HttpServletResponse response = (HttpServletResponse) res;  
    		  
            HttpServletRequest reqs = (HttpServletRequest) req;  
            /*
             * 跨域设置允所有请求跨域 
             * 如果允许指定的客户端跨域设置: http://127.0.0.1:8020
             */
            response.setHeader("Access-Control-Allow-Origin","*");  
            response.setHeader("Access-Control-Allow-Credentials", "true");  
            response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");  
            response.setHeader("Access-Control-Max-Age", "3600");  
            response.setHeader("Access-Control-Allow-Headers", "Content-Type");  
            if (((HttpServletRequest) req).getMethod().equals("OPTIONS")) {
                response.getWriter().println("ok");
                return;
            }
    
            chain.doFilter(req, res);  
    	}
    
    	@Override
    	public void destroy() {
    		// TODO Auto-generated method stub
    		
    	}
    
    }

application.properties

# 指定服务端口
    server.port=9092
    # 指定日志文件配置
    logging.config=classpath:logback.xml

logback.xml

<?xml version="1.0" encoding="UTF-8"?> 
      
      
      
      
      
      
      
    <configuration scan="true" scanPeriod="60 seconds" debug="false">  
          
        <property name="log_dir" value="/logs/single" />  
          
        <property name="maxHistory" value="30"/>  
      
      
          
        <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">  
              
            <encoder>  
                <pattern>%d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger -%msg%n</pattern>  
            </encoder>  
        </appender>  
          
          
          
          
        <appender name="ERROR" class="ch.qos.logback.core.rolling.RollingFileAppender">  
              
            <filter class="ch.qos.logback.classic.filter.LevelFilter">  
                <level>ERROR</level>  
                <onMatch>ACCEPT</onMatch>  
                <onMismatch>DENY</onMismatch>  
            </filter>  
              
            <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">  
                  
                <fileNamePattern>${log_dir}/%d{yyyy-MM-dd}/error.log</fileNamePattern>  
                  
                <maxHistory>${maxHistory}</maxHistory>  
            </rollingPolicy>  
                      
            <encoder>  
                <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger - %msg%n</pattern>  
            </encoder>  
        </appender>  
          
          
          
        <appender name="WARN" class="ch.qos.logback.core.rolling.RollingFileAppender">  
              
            <filter class="ch.qos.logback.classic.filter.LevelFilter">  
                <level>WARN</level>  
                <onMatch>ACCEPT</onMatch>  
                <onMismatch>DENY</onMismatch>  
            </filter>  
            <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">  
                <fileNamePattern>${log_dir}/%d{yyyy-MM-dd}/warn.log  
                </fileNamePattern>  
                <maxHistory>${maxHistory}</maxHistory>  
            </rollingPolicy>  
            <encoder>  
                <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger - %msg%n</pattern>  
            </encoder>  
        </appender>  
          
          
          
        <appender name="INFO" class="ch.qos.logback.core.rolling.RollingFileAppender">  
              
            <filter class="ch.qos.logback.classic.filter.LevelFilter">  
                <level>INFO</level>  
                <onMatch>ACCEPT</onMatch>  
                <onMismatch>DENY</onMismatch>  
            </filter>  
            <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">  
                <fileNamePattern>${log_dir}/%d{yyyy-MM-dd}/info.log  
                </fileNamePattern>  
                <maxHistory>${maxHistory}</maxHistory>  
            </rollingPolicy>  
            <encoder>  
                <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger - %msg%n</pattern>  
            </encoder>  
        </appender>  
          
          
          
        <appender name="DEBUG" class="ch.qos.logback.core.rolling.RollingFileAppender">  
            <filter class="ch.qos.logback.classic.filter.LevelFilter">  
                <level>DEBUG</level>  
                <onMatch>ACCEPT</onMatch>  
                <onMismatch>DENY</onMismatch>  
            </filter>  
            <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">  
                <fileNamePattern>${log_dir}/%d{yyyy-MM-dd}/debug.log  
                </fileNamePattern>  
                <maxHistory>${maxHistory}</maxHistory>  
            </rollingPolicy>  
            <encoder>  
                <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger - %msg%n</pattern>  
            </encoder>  
        </appender>  
        
        <logger name="org.springframework.web"/>
        <logger name="com.single" />
    		
          
          
        <root level="ERROR">  
              
            <appender-ref ref="STDOUT" />  
              
            <appender-ref ref="ERROR" />  
            <appender-ref ref="INFO" />  
            <appender-ref ref="WARN" />  
            <appender-ref ref="DEBUG" />  
        </root>  
    </configuration>

PostMan 模拟工具效果展示：

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA5Zyo5aWL5paX55qE5aSn6YGT_size_20_color_FFFFFF_t_70_g_se_x_16][]

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA5Zyo5aWL5paX55qE5aSn6YGT_size_20_color_FFFFFF_t_70_g_se_x_16 1][]

基本功能已经完成，静待前端工程师的对接。

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