Struts2框架实现文件上传

开发环境
系统:Windows10 版本1709
JDK:1.8.0_161 32位
IDE: Spring Tool Suite 3.7.3 32位
Struts2版本:2.3.24
服务器版本:apache-tomcat-7.0.52

单文件的上传

环境搭建

导入必要的jar包

必须有commons-fileupload-1.3.1.jar包. 在开发Struts2框架必备的13个jar包中,包含了此jar包.

在web.xml中配置核心的过滤器

<filter><filter-name>struts</filter-name><filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
</filter><filter-mapping><filter-name>struts</filter-name><url-pattern>/*</url-pattern>        
</filter-mapping>

在src目录下创建struts.xml文件,并导入约束

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN""http://struts.apache.org/dtds/struts-2.3.dtd">

文件上传的浏览器的三要素

表单的提交方式必须为post
表单中必须有一个<\input type="file">
表单设置enctype="multipart/form-data"

创建一个upload.jsp页面

<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%>
<!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>Insert title here</title>
</head>
<body><form action="${pageContext.request.contextPath}/up" method="post" enctype="multipart/form-data"><input type="file" name="upload"><input type="summit" value="上传"></form>
</body>
</html>

文件上传的服务器端

创建一个UploadAction的java类

public class UploadAction {private File upload;//定义一个File ,变量名要与jsp中的input标签的name一致private String uploadContentType;//上传文件的mimeType类型private String uploadFileName;//上传文件的名称public File getUpload() {return upload;}public void setUpload(File upload) {this.upload = upload;}public String getUploadContentType() {return uploadContentType;}public void setUploadContentType(String uploadContentType) {this.uploadContentType = uploadContentType;}public String getUploadFileName() {return uploadFileName;}public void setUploadFileName(String uploadFileName) {this.uploadFileName = uploadFileName;}public void uploadFile(){try {//在WebContent下新建一个upload的文件夹,获取其在服务器的绝对磁盘路径String path = ServletActionContext.getServletContext().getRealPath("/upload");//创建一个服务器端的文件File dest = new File(path,uploadFileName);//完成文件上传的操作FileUtils.copyFile(upload, dest);} catch (IOException e) {e.printStackTrace();}}
}

在struts.xml中进行如下的配置

<struts><!--配置开发者模式,可以显示更加详细的错误信息 --><constant name="struts.devMode" value="true"></constant><constant name="struts.multipart.maxSize" value="20971520"></constant><package name="upload_demo" extends="struts-default" namespace="/" ><!-- <interceptors><interceptor-stack name="myStack"><interceptor-ref name="fileUpload">设置上传文件允许的后缀名,多个使用逗号隔开 <param name="allowedExtensions">avi,txt</param></interceptor-ref>配置了其他的拦截器,就需要手动导入默认的拦截器<interceptor-ref name="defaultStack"></interceptor-ref></interceptor-stack></interceptors> --><action class="com.thc.action.UploadAction" method="uploadFile" name="up"><result name="input">/error.jsp</result><interceptor-ref name="fileUpload"><param name="maximumSize"></param><!-- 设置每一个action允许的上传文件的大小 --><param name="allowedTypes"></param><!--设置上传允许的文件的mimeType类型，多个使用逗号分开--><param name="allowedExtensions">bmp,txt</param><!-- 设置上传文件允许的后缀名，多个使用逗号分开 --></interceptor-ref><interceptor-ref name="defaultStack"></interceptor-ref></action></package>
</struts>

使用Struts2框架实现文件上传.在页面的<input type="file" name="upload">name属性的名字,必须与文件上传的Java类中定义的File类型变量的名字一样.

文件类型和文件名称的变量名也必须为name之后的拼接

注意上传的文件是个临时文件,服务器重启后,文件就不存在了. 要想永久的保存,需要指定一个本地硬盘的目录.

文件上传出现的问题以及解决方案

文件的大小问题

如果上传一个较大的文件,控制台会报空指针异常.这个空指针的异常信息不够详细.

把当前的文件上传的java类继承ActionSupport类底层会去调用保存错误信息的方法. 并且在struts.xml文件中,开启开发者模式.

<constant name="struts.devMode" value="true"></constant>

再次上传一个较大的文件,会发现这次在报的错误不再是空指针异常. 控制台报错信息如下:

[http-bio-8080-exec-10] ERROR org.apache.struts2.dispatcher.Dispatcher - Could not find action or result
/strust2_fileupload/up
com.opensymphony.xwork2.config.ConfigurationException: No result defined for action com.thc.action.UploadAction and result input

这是说当前的文件上传的java类没有配置result 的input视图.

这是因为Struts底层的拦截器如果出现问题,那么就会把错误信息存储到action中, workflow的拦截器负责控制跳转到指定的input视图.

在struts.xml中的\ 标签中配置\名为input的视图 ,标签体为error.jsp

<struts><!--配置开发者模式,可以显示更加详细的错误信息 --><constant name="struts.devMode" value="true"></constant><package name="upload_demo" extends="struts-default" namespace="/" ><action name="up" class="com.thc.action.UploadAction" method="uploadFile"><result name="input">/error.jsp</result></action></package>
</struts>

在WebContent下新建一个error.jsp页面

在jsp页面的顶部导入struts2框架的标签

<%@taglib prefix="s" uri="/struts-tags" %>

在页面中写上struts的标签<s:actionerror/><s:fielderror/> 用来显示提示错误信息

<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%><%@taglib prefix="s" uri="/struts-tags" %>
<!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>错误信息显示页面</title>
</head>
<body><h3>文件上传错误信息显示页面</h3><s:actionerror/><s:fielderror/>
</body>
</html>

以上的操作做完了之后, 再次上传一个较大的文件.会在浏览器上看到如下的错误提示信息

Request exceeded allowed size limit! Max size allowed is: 2,097,152 but request was: 1,346,882,290!

提示是说,请求超出了最大的允许界限

原因是在struts2框架default.properties配置文件中,定义了默认的文件上传大小为2097152字节(byte)为2M.

在struts.xml的配置文件中,修改这个常量的大小.

<constant name="struts.multipart.maxSize" value="20971520"></constant>

修改为20M. 再次上传一个小于20M的文件后,就不会报错了. 这个文件大小的范围,依据实际的需求而设定.

以上的改变常量方法是对所有的action生效,要想仅仅使一个action生效,设置上传文件的大小,需要在<action>标签中设置

查看FileUploadInterceptor这个拦截器的源码

发现有如下的属性:

    protected Long maximumSize;protected Set<String> allowedTypesSet = Collections.emptySet();protected Set<String> allowedExtensionsSet = Collections.emptySet();

分别代表的是设置文件的最大大小,设置运行的文件类型,设置文件运行的后缀名.

有如下的set方法,设置参数.

 /*** Sets the allowed extensions** @param allowedExtensions A comma-delimited list of extensions*/public void setAllowedExtensions(String allowedExtensions) {allowedExtensionsSet = TextParseUtil.commaDelimitedStringToSet(allowedExtensions);}/*** Sets the allowed mimetypes** @param allowedTypes A comma-delimited list of types*/public void setAllowedTypes(String allowedTypes) {allowedTypesSet = TextParseUtil.commaDelimitedStringToSet(allowedTypes);}/*** Sets the maximum size of an uploaded file** @param maximumSize The maximum size in bytes*/public void setMaximumSize(Long maximumSize) {this.maximumSize = maximumSize;}

上传文件允许的后缀名

在如下的struts.xml中,配置如下:

<action name="up" class="com.thc.action.UploadAction" method="uploadFile"><result name="input">/error.jsp</result><interceptor-ref name="fileUpload"><!--设置上传文件允许的后缀名,多个使用逗号隔开  --><param name="allowedExtensions">avi,txt</param></interceptor-ref><!-- 配置了其他的拦截器,就需要手动导入默认的拦截器 --><interceptor-ref name="defaultStack"></interceptor-ref>
</action>

设置了只允许上传后缀名为avi,txt结尾的文件

实验上传一个.doc后缀名的文件

浏览器上会有如下的报错信息 :提示了doc后缀名是不允许的.

File extension not allowed: upload "测试.doc" "upload_7cd79feb_ad18_40cb_a401_f74b2d2f27a1_00000000.tmp" application/msword

多文件的上传

新建一个multipload.jsp的页面

<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%>
<!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>Insert title here</title>
</head>
<body><h2>多文件的上传</h2><form action="${pageContext.request.contextPath}/multiup" method="post" enctype="multipart/form-data"><input type="file" name="upload"><br/><input type="file" name="upload"><br/><input type="file" name="upload"><input type="submit" value="上传"></form>
</body>
</html>

设置了三个文件上传框

新建一个MultiUploadAction

在原来的属性中,把FIle设置为List集合,或者是数组.

以下为设置了数组.遍历每一个数组的元素.通过索引获取数组的文件名和文件.

public class MultiUploadAction extends ActionSupport {private File[] upload;//定义一个File ,变量名要与jsp中的input标签的name一致private String[] uploadContentType;//上传文件的mimeType类型private String[] uploadFileName;//上传文件的名称public File[] getUpload() {return upload;}public void setUpload(File[] upload) {this.upload = upload;}public String[] getUploadContentType() {return uploadContentType;}public void setUploadContentType(String[] uploadContentType) {this.uploadContentType = uploadContentType;}public String[] getUploadFileName() {return uploadFileName;}public void setUploadFileName(String[] uploadFileName) {this.uploadFileName = uploadFileName;}public void uploadFile(){//在WebContent下新建一个upload的文件夹,获取其在服务器的绝对磁盘路径String path = ServletActionContext.getServletContext().getRealPath("/upload");try {for (int i = 0; i < upload.length; i++) {//创建一个服务器端的文件File dest = new File(path,uploadFileName[i]);//完成文件上传的操作FileUtils.copyFile(upload[i], dest);}} catch (IOException e) {e.printStackTrace();}}
}

以下是List集合的方式

通过list.size()来控制集合的遍历,通过get(index)来获取集合的每一个元素

public class MultiUploadAction extends ActionSupport {private List<File> upload;//定义一个File ,变量名要与jsp中的input标签的name一致private List<String> uploadContentType;//上传文件的mimeType类型private List<String> uploadFileName;//上传文件的名称public List<File> getUpload() {return upload;}public void setUpload(List<File> upload) {this.upload = upload;}public List<String> getUploadContentType() {return uploadContentType;}public void setUploadContentType(List<String> uploadContentType) {this.uploadContentType = uploadContentType;}public List<String> getUploadFileName() {return uploadFileName;}public void setUploadFileName(List<String> uploadFileName) {this.uploadFileName = uploadFileName;}public void uploadFile(){//在WebContent下新建一个upload的文件夹,获取其在服务器的绝对磁盘路径String path = ServletActionContext.getServletContext().getRealPath("/upload");try {for (int i = 0; i < upload.size(); i++) {//创建一个服务器端的文件File dest = new File(path,uploadFileName.get(i));//完成文件上传的操作FileUtils.copyFile(upload.get(i), dest);}} catch (IOException e) {e.printStackTrace();}}
}

在配置文件中新建一个action的配置

<action name="multiup" class="com.thc.action.MultiUploadAction" method="uploadFile"><result name="input">/error.jsp</result>
</action>

多文件上传的测试

在服务器中部署项目,访问multipload.jsp页面

选择三个小于2M的文件进行选择文件上传测试.点击上传后,成功在服务器的upload文件夹下上传了文件

注解开发

注解配置文件上传

注解的方式配置action类单个的文件上传
在class 上配置namespace 和parentPackage
注意单文件的上传@ParentPackage的值为"upload_demo"，因为在struts.xml设置了拦截器，起了包名为"upload_demo"
在方法上配置@Action @InterceptorRef @Result

@Namespace("/")
@ParentPackage("upload_demo")
public class UploadAction extends ActionSupport {private File upload;//定义一个File ,变量名要与jsp中的input标签的name一致private String uploadContentType;//上传文件的mimeType类型private String uploadFileName;//上传文件的名称public File getUpload() {return upload;}public void setUpload(File upload) {this.upload = upload;}public String getUploadContentType() {return uploadContentType;}public void setUploadContentType(String uploadContentType) {this.uploadContentType = uploadContentType;}public String getUploadFileName() {return uploadFileName;}public void setUploadFileName(String uploadFileName) {this.uploadFileName = uploadFileName;}@Action(value="up",interceptorRefs={@InterceptorRef("myStack")},results={@Result(name="input",location="/error.jsp")})public void uploadFile(){try {//在WebContent下新建一个upload的文件夹,获取其在服务器的绝对磁盘路径String path = ServletActionContext.getServletContext().getRealPath("/upload");//创建一个服务器端的文件File dest = new File(path,uploadFileName);//完成文件上传的操作FileUtils.copyFile(upload, dest);} catch (IOException e) {e.printStackTrace();}}
}

注解的方式的配置多文件的上传

@Namespace("/")
@ParentPackage("struts-default")
public class MultiUploadAction extends ActionSupport {private List<File> upload;//定义一个File ,变量名要与jsp中的input标签的name一致private List<String> uploadContentType;//上传文件的mimeType类型private List<String> uploadFileName;//上传文件的名称public List<File> getUpload() {return upload;}public void setUpload(List<File> upload) {this.upload = upload;}public List<String> getUploadContentType() {return uploadContentType;}public void setUploadContentType(List<String> uploadContentType) {this.uploadContentType = uploadContentType;}public List<String> getUploadFileName() {return uploadFileName;}public void setUploadFileName(List<String> uploadFileName) {this.uploadFileName = uploadFileName;}@Action(value="multiup",results={@Result(name="input",location="/error.jsp")})public void uploadFile(){//在WebContent下新建一个upload的文件夹,获取其在服务器的绝对磁盘路径String path = ServletActionContext.getServletContext().getRealPath("/upload");try {for (int i = 0; i < upload.size(); i++) {//创建一个服务器端的文件File dest = new File(path,uploadFileName.get(i));//完成文件上传的操作FileUtils.copyFile(upload.get(i), dest);}} catch (IOException e) {e.printStackTrace();}}
}

```

struts.xml中的内容如下

<struts><!--配置开发者模式,可以显示更加详细的错误信息 --><constant name="struts.devMode" value="true"></constant><constant name="struts.multipart.maxSize" value="20971520"></constant><package name="upload_demo" extends="struts-default" namespace="/" ><interceptors><interceptor-stack name="myStack"><interceptor-ref name="fileUpload"><!--设置上传文件允许的后缀名,多个使用逗号隔开  --><param name="allowedExtensions">avi,txt</param></interceptor-ref><!-- 配置了其他的拦截器,就需要手动导入默认的拦截器 --><interceptor-ref name="defaultStack"></interceptor-ref></interceptor-stack></interceptors></package>
</struts>