Java 实现图片等比例缩略图（Thumbnailator + Jsp+SpringMVC）

矫情吗；* 2022-08-22 00:14 319阅读 0赞

> Web应用为上传图片生成缩略图是常见的基本功能，通过缩略图生成提高了信息浏览时的性能，在保证用户使用体验的同时减少了数据传输量。本次以实例的方式，讲解如何使用使用Java实现图片等比例缩略图生成功能。

#### **效果查看** ####

![这里写图片描述][20160508155415042]

![这里写图片描述][20160508155425995]

![这里写图片描述][20160508155437167]

#### **代码编写** ####

Thumbnailator 是一个为Java界面更流畅的缩略图生成库。从API提供现有的图像文件和图像对象的缩略图中简化了缩略过程，两三行代码就能够从现有图片生成缩略图，且允许微调缩略图生成，同时保持了需要写入到最低限度的代码量。

**1.导入相关的包**

![这里写图片描述][20160508155807272]

**2.配置web.xml**

web.xml

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
      <display-name>thumbnail</display-name>
      
        <servlet>
            <servlet-name>dispatcherServlet</servlet-name>
            <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
            <init-param>
                <param-name>contextConfigLocation</param-name>
                <param-value>classpath:springmvc.xml</param-value>
            </init-param>
            <load-on-startup>1</load-on-startup>
        </servlet>
    
        <servlet-mapping>
            <servlet-name>dispatcherServlet</servlet-name>
            <url-pattern>/</url-pattern>
        </servlet-mapping>
      <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
      </welcome-file-list>
    </web-app>

**3.配置 springmvc.xml**

springmvc.xml

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xmlns:mvc="http://www.springframework.org/schema/mvc" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd">
    
        <mvc:default-servlet-handler/>
        <mvc:annotation-driven/>    
        
        <context:component-scan base-package="com.wenteryan"></context:component-scan>
    
        
        <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
            <property name="prefix" value="/"></property>
            <property name="suffix" value=".jsp"></property>
            <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"></property>
        </bean>
    
        <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
            <property name="defaultEncoding" value="UTF-8"></property>
            <property name="maxUploadSize" value="10485760000"></property>
            <property name="maxInMemorySize" value="40960"></property>
        </bean>
    
    </beans>

**4.编写Action**

ThumbnailAction.java

@Controller
    public class ThumbnailAction { 
    
        public UploadService uploadService ;
        public ThumbnailService thumbnailService ;
    
        @RequestMapping(value="/thumbnail", method=RequestMethod.POST)
        public ModelAndView thumbnail(@RequestParam("image")CommonsMultipartFile file, HttpSession session) throws Exception {
            String uploadPath = "/images" ;
            String realUploadPath = session.getServletContext().getRealPath(uploadPath) ;
            String imageUrl = uploadService.uploadImage(file, uploadPath, realUploadPath) ;
            String thumbImageUrl = thumbnailService.thumbnail(file, uploadPath, realUploadPath) ;
            ModelAndView ret = new ModelAndView() ;
            ret.addObject("imagesUrl", imageUrl) ;
            ret.addObject("thumbnailUrl", thumbImageUrl) ;
            ret.setViewName("thumbnail");   
            return ret ;
        }
    
        @Autowired
        public void setUploadService(UploadService uploadService) {
            this.uploadService = uploadService;
        }
        @Autowired
        public void setThumbnailService(ThumbnailService thumbnailService) {
            this.thumbnailService = thumbnailService;
        }
    }

**5.编写service**

ThumbnailService .java

@Service
    public class ThumbnailService { 
    
        public static final int WIDTH = 100 ;
        public static final int HEIGHT = 100 ;
    
        public String thumbnail(CommonsMultipartFile file, String uploadPath, String realUploadPath) {
    
            try {
                String des = realUploadPath +"/thum_" + file.getOriginalFilename() ;
            Thumbnails.of(file.getInputStream()).size(WIDTH, HEIGHT).toFile(des); ;
            } catch(Exception e) {
                e.printStackTrace() ;
            } 
            return uploadPath + "/thum_" + file.getOriginalFilename() ;
        }
    }

UploadService .java

@Service
    public class UploadService {
    
        public String uploadImage(CommonsMultipartFile file, String uploadPath, String realUploadPath) {
            InputStream is = null ;
            OutputStream os = null ;
    
            try {
                is = file.getInputStream() ;
                String des = realUploadPath + "\\" + file.getOriginalFilename() ;
                os = new FileOutputStream(des) ;
                byte[] buffer = new byte[1024] ;
                int len = 0 ;
                while((len=is.read(buffer))>0) {
                    os.write(buffer);
                }
            } catch(Exception e) {
                e.printStackTrace();
            } finally {
                if(is!=null) {
                    try {
                        is.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
    
                if(os!=null) {
                    try {
                        os.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
            return uploadPath + "/" + file.getOriginalFilename() ;
        }
    }

**6.编写 jsp 文件**

index.jsp

<div class="panel panel-warning">
        <div class="panel-heading"><h2>Java 实现图片等比例缩略图</h2></div>
        <div class="panel-body">
        <form action="thumbnail" method="post" enctype="multipart/form-data">
            <h2>请选择上传的图片</h2>
            <div class="form-group">
            <input type="file" name="image" id="image" />
            </div>
            <div class="form-group">
            <button class="btn btn-success" type="submit">开始上传</button>
            </div>
        </form>
        </div>
    </div>

thumbnail.jsp

<div class="panel panel-warning">
        <div class="panel-heading"><h2>原图片与缩略图</h2></div>
        <div class="panel-body">
            <img alt="" src="${pageContext.request.contextPath }${imagesUrl }"/>
            <img alt="" src="${pageContext.request.contextPath }${thumbnailUrl }"/>
            <br><br>
            <a class="btn btn-warning" href="${pageContext.request.contextPath }">返回</a>
        </div>
    </div>

#### **技术总结** ####

实现图片缩略图的好处总结如下：

1、节省存储空间。  
2、更加灵活响应运营部的多尺寸图片需求。  
3、提高程序性能和效率。

[20160508155415042]: /images/20220724/0e9ad2ecf5e1443588691fd499bea237.png
[20160508155425995]: /images/20220724/93557fc3e8d748649bc10252dda78f76.png
[20160508155437167]: /images/20220724/1935712c4c9c4fdd8abe6b7b9d171a88.png
[20160508155807272]: /images/20220724/78b08b3b149e468f8622af27d4725a0c.png