Struts2实现单文件或多文件上传功能

实现文件上传功能的步骤：

1. 配置文件上传参数：在Strust2的配置文件struts.xml中设置maxFileSize参数，设置单个文件最大大小；以及maxRequestSize参数，设置总文件大小。

<constant name="struts.multipart.maxFileSize" value="5 * 1024 * 1024" />
<constant name="struts.multipart.maxRequestSize" value="10 * 1024 * 1024"/>

1. 编写表单：在页面上添加一个用于文件上传的表单，设置属性enctype="multipart/form-data"。

<form action="upload_file" enctype="multipart/form-data" method="POST">
  <input type="file" name="uploadFile" />
  <input type="submit" value="上传文件" />
</form>

1. 编写Action：实现文件上传功能的核心部分，主要分为单文件上传和多文件上传两种方式。

单文件上传示例：

public class UploadAction extends ActionSupport {

    private File uploadFile;
    private String uploadFileFileName;
    private String uploadFileContentType;

    public String execute() throws Exception {

        // 检查是否选择了文件
        if (uploadFile == null) {
            addActionError("请选择要上传的文件");
            return ERROR;
        }

        // 检查上传文件的类型
        if (!"image/jpeg".equals(uploadFileContentType)) {
            addActionError("上传文件必须是jpeg格式");
            return ERROR;
        }

        // 检查上传文件的大小
        if (uploadFile.length() > 1024 * 1024) {
            addActionError("上传文件大小不能超过1MB");
            return ERROR;
        }

        // 上传文件到服务器
        FileOutputStream fos = new FileOutputStream("上传目录/" + uploadFileFileName);
        FileInputStream fis = new FileInputStream(uploadFile);
        byte[] buffer = new byte[1024];
        int len;
        while ((len = fis.read(buffer)) > 0) {
            fos.write(buffer, 0, len);
        }
        fis.close();
        fos.close();

        // 返回上传成功页面
        return SUCCESS;
    }

    public File getUploadFile() {
        return uploadFile;
    }

    public void setUploadFile(File uploadFile) {
        this.uploadFile = uploadFile;
    }

    public String getUploadFileFileName() {
        return uploadFileFileName;
    }

    public void setUploadFileFileName(String uploadFileFileName) {
        this.uploadFileFileName = uploadFileFileName;
    }

    public String getUploadFileContentType() {
        return uploadFileContentType;
    }

    public void setUploadFileContentType(String uploadFileContentType) {
        this.uploadFileContentType = uploadFileContentType;
    }

}

多文件上传示例：

public class MultiFileUploadAction extends ActionSupport {

    private List<File> uploadFiles = new ArrayList<File>();
    private List<String> uploadFilesFileName = new ArrayList<String>();
    private List<String> uploadFilesContentType = new ArrayList<String>();

    public String execute() throws Exception {

        // 检查是否选择了文件
        if (uploadFiles == null || uploadFiles.size() == 0) {
            addActionError("请选择要上传的文件");
            return ERROR;
        }

        // 逐个检查并上传文件
        for (int i = 0; i < uploadFiles.size(); i++) {

            // 检查上传文件的类型
            if (!"image/jpeg".equals(uploadFilesContentType.get(i))) {
                addActionError("上传文件必须是jpeg格式");
                continue;
            }

            // 检查上传文件的大小
            if (uploadFiles.get(i).length() > 1024 * 1024) {
                addActionError("上传文件大小不能超过1MB");
                continue;
            }

            // 上传文件到服务器
            FileOutputStream fos = new FileOutputStream("上传目录/" + uploadFilesFileName.get(i));
            FileInputStream fis = new FileInputStream(uploadFiles.get(i));
            byte[] buffer = new byte[1024];
            int len;
            while ((len = fis.read(buffer)) > 0) {
                fos.write(buffer, 0, len);
            }
            fis.close();
            fos.close();

        }

        // 返回上传成功页面
        return SUCCESS;
    }

    public List<File> getUploadFiles() {
        return uploadFiles;
    }

    public void setUploadFiles(List<File> uploadFiles) {
        this.uploadFiles = uploadFiles;
    }

    public List<String> getUploadFilesFileName() {
        return uploadFilesFileName;
    }

    public void setUploadFilesFileName(List<String> uploadFilesFileName) {
        this.uploadFilesFileName = uploadFilesFileName;
    }

    public List<String> getUploadFilesContentType() {
        return uploadFilesContentType;
    }

    public void setUploadFilesContentType(List<String> uploadFilesContentType) {
        this.uploadFilesContentType = uploadFilesContentType;
    }

}

1. 测试：在Web容器中启动应用后，访问上传文件的页面，在表单中选择文件并上传，上传的文件保存在服务器的指定目录中。

总结：通过对Struts2框架的配置，添加文件上传的表单，编写Action的核心代码，就能比较简单地实现文件上传功能。