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

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

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



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>
<!-- 配置 SpringMVC 的 DispatcherServlet -->
<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/>
<!-- 配置自定扫描的包 -->
<context:component-scan base-package="com.wenteryan"></context:component-scan>

<!-- 配置视图解析器: 如何把 handler 方法返回值解析为实际的物理视图 -->
<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。