一、准备
1. 下载 commons-fileupload 库,下载地址:http://commons.apache.org/fileupload/
2. 下载 commons-fileupload 依赖库 commons-io,下载地址:http://commons.apache.org/io/
二、代码
该组件支持单文件上传和多文件上传两种方式,首先定义一个基类放置公共属性:
FileUploadBase.java
import java.io.File;
import java.util.HashMap;
import java.util.Map;import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;public abstract class FileUploadBase {
protected Map<String, String> parameters = new HashMap<String, String>();// 保存普通form表单域
protected String encoding = "utf-8"; // 字符编码,当读取上传表单的各部分时会用到该encodingprotected UploadFileFilter filter = null; // 文件过滤器, 默认为NULL 不过滤
/**
* The directory in which uploaded files will be stored, if stored on disk.
*/
protected int sizeThreshold = DiskFileItemFactory.DEFAULT_SIZE_THRESHOLD;/**
*
* The maximum size permitted for the complete request, as opposed to
*
* {@link #fileSizeMax}. A value of -1 indicates no maximum.
*
*/
protected long sizeMax = -1;/**
* The directory in which uploaded files will be stored, if stored on disk.
*/
protected File repository;
public String getParameter(String key) {
return parameters.get(key);
}public String getEncoding() {
return encoding;
}public void setEncoding(String encoding) {
this.encoding = encoding;
}/**
* 获取上传文件最大的大小,单位为Byte(字节),为-1时表示无限制
* @return
*/
public long getSizeMax() {
return sizeMax;
}/**
* 设置上传文件最大的大小,单位为Byte(字节),为-1时表示无限制
* @param sizeMax
*/
public void setSizeMax(long sizeMax) {
this.sizeMax = sizeMax;
}public int getSizeThreshold() {
return sizeThreshold;
}public void setSizeThreshold(int sizeThreshold) {
this.sizeThreshold = sizeThreshold;
}/**
* Returns the directory used to temporarily store files that are larger
* than the configured size threshold.
*
* @return The directory in which temporary files will be located.
*
* @see #setRepository(java.io.File)
*
*/
public File getRepository() {
return repository;
}/**
* Sets the directory used to temporarily store files that are larger than
* the configured size threshold.
*
* @param repository
* The directory in which temporary files will be located.
*
* @see #getRepository()
*
*/
public void setRepository(File repository) {
this.repository = repository;
}
/**
* 获取参数列表
* @return
*/
public Map<String, String> getParameters() {
return parameters;
}/**
* 获取过滤器
* @return
*/
public UploadFileFilter getFilter() {
return filter;
}/**
* 设置文件过滤器,不符合过滤器规则的将不被上传
* @param filter
*/
public void setFilter(UploadFileFilter filter) {
this.filter = filter;
}
/**
* 验证文件是否有效
* @param item
* @return
*/
protected boolean isValidFile(FileItem item){
return item == null || item.getName() == "" || item.getSize() == 0 || (filter != null && !filter.accept(item.getName())) ? false : true;
}
}
SingleFileUpload.java
import java.io.File;
import java.io.UnsupportedEncodingException;
import java.util.List;import javax.servlet.http.HttpServletRequest;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;public class SingleFileUpload extends FileUploadBase {
private FileItem fileItem;/**
*
* @param request
* @throws UnsupportedEncodingException
*/
public void parseRequest(HttpServletRequest request)
throws UnsupportedEncodingException {DiskFileItemFactory factory = new DiskFileItemFactory();
factory.setSizeThreshold(sizeThreshold);
if (repository != null)
factory.setRepository(repository);ServletFileUpload upload = new ServletFileUpload(factory);
upload.setHeaderEncoding(encoding);
try {
List<FileItem> items = upload.parseRequest(request);for (FileItem item : items) {
if (item.isFormField()) {
String fieldName = item.getFieldName();
String value = item.getString(encoding);
parameters.put(fieldName, value);
} else {if (!super.isValidFile(item)) {
continue;
}
if (fileItem == null)
fileItem = item;
}
}} catch (FileUploadException e) {
e.printStackTrace();
}
}/**
* 上传文件, 调用该方法之前必须先调用 parseRequest(HttpServletRequest request)
* @param fileName 完整文件路径
* @throws Exception
*/
public void upload(String fileName) throws Exception {
File file = new File(fileName);
uploadFile(file);
}/**
* 上传文件, 调用该方法之前必须先调用 parseRequest(HttpServletRequest request)
* @param parent 存储的目录
* @throws Exception
*/
public void upload(File parent) throws Exception {
if (fileItem == null)
return;String name = fileItem.getName();
File file = new File(parent, name);
uploadFile(file);
}
private void uploadFile(File file) throws Exception{
if (fileItem == null)
return;long fileSize = fileItem.getSize();
if (sizeMax > -1 && fileSize > super.sizeMax){
String message = String.format("the request was rejected because its size (%1$s) exceeds the configured maximum (%2$s)", fileSize, super.sizeMax);
throw new org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException(message, fileSize, super.sizeMax);
}
String name = fileItem.getName();
fileItem.write(file);
}
/**
* 获取文件信息
* 必须先调用 parseRequest(HttpServletRequest request)
* @return
*/
public FileItem getFileItem() {
return fileItem;
}
}
MutiFileUpload.java
import java.io.File;
import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;import javax.servlet.http.HttpServletRequest;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;public class MutiFileUpload extends FileUploadBase {
private Map<String, FileItem> files;// 保存上传的文件
private long filesSize = 0; // 所有文件的总大小public void parseRequest(HttpServletRequest request)
throws UnsupportedEncodingException {files = new HashMap<String, FileItem>();
// Create a factory for disk-based file items
DiskFileItemFactory factory = new DiskFileItemFactory();
factory.setSizeThreshold(sizeThreshold);
if (repository != null)
factory.setRepository(repository);ServletFileUpload upload = new ServletFileUpload(factory);
upload.setHeaderEncoding(encoding);
try {
List<FileItem> items = upload.parseRequest(request);for (FileItem item : items) {
if (item.isFormField()) {
String fieldName = item.getFieldName();
String value = item.getString(encoding);
parameters.put(fieldName, value);
} else {if (super.isValidFile(item)) {
continue;
}String fieldName = item.getFieldName();
files.put(fieldName, item);
filesSize += item.getSize();
}
}} catch (FileUploadException e) {
e.printStackTrace();
}
}/**
* 上传文件, 调用该方法之前必须先调用 parseRequest(HttpServletRequest request)
* @param parent 文件存储的目录
* @throws Exception
*/
public void upload(File parent) throws Exception {
if (files.isEmpty())
return;
if (sizeMax > -1 && filesSize > super.sizeMax){
String message = String.format("the request was rejected because its size (%1$s) exceeds the configured maximum (%2$s)", filesSize, super.sizeMax);
throw new SizeLimitExceededException(message, filesSize, super.sizeMax);
}for (String key : files.keySet()) {
FileItem item = files.get(key);
String name = item.getName();File file = new File(parent, name);
item.write(file);
}
}public Map<String, FileItem> getFiles() {
return files;
}}
UploadFileFilter.java
public interface UploadFileFilter {
/**
* 通过文件名后缀判断文件是否被接受
* @param filename 文件名,不包括路径
* @return
*/
public boolean accept(String filename);
}
这样在 Servlet 中我们就可以通过简单的代码实现文件的上传了:
SingleFileUpload upload = new SingleFileUpload();
upload.parseRequest(request);
File parent = new File("C:\\upload\\");try {
upload.upload(parent);
}
catch(org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException e){
// 文件大小超出最大值
e.printStackTrace();
}
catch (Exception e) {
e.printStackTrace();
}
三、FileItem类的常用方法
1. boolean isFormField()
isFormField方法用来判断FileItem对象里面封装的数据是一个普通文本表单字段,还是一个文件表单字段。如果是普通文本表单字段,返回一个true否则返回一个false。因此可以用该方法判断是否是普通表单域还是文件上传表单域。
2. String getName()
getName方法用来获得文件上传字段中的文件名。
3. String getFieldName()
getFieldName方法用来返回表单标签的name属性的值。
4. void write(File file)
write方法将FileItem对象中的内容保存到某个指定的文件中。如果FileItem对象中的内容是保存在某个临时文件中,该方法完成后,临时文件可以会被删除。该方法也可以将普通表单字段保存在一个文件中,但最主要的用途是把上传的文件内容保存在本地文件系统中。
5. String getString()
getString()方法将FileItem对象中保存的数据流内容以一个字符串返回。它有两个重载形式:public java.lang.String getString()和public java.lang.String getString(java.lang.String encodeing) throws java.io.UnsupportedEncodingException。前者使用缺省的字符集编码将主体内容转换成字符串,后者使用参数指定的字符集编码。如果在读取普通表单字段元素的内容时,出现了乱码现象,可以调用第二个方法,并传入正确的字符集编码名称。
6. String getContentType()
此方法用来获得上传文件的类型,即标段字段元素描述头属性“content-type”的值,如image/jpeg。如果FileItem对象对应的是普通的表单字段,将返回null。
7. boolean isInMemory()
判断FileItem对象封装的数据是保存在内存中还是硬盘中。
8. void delete()
此方法用来清空FileItem对象中封装的主体内容,如果内容是被保存在临时文件中,该方法会把临时文件删除。
9. InputStream getInputStream()
以流的形式返回上传文件的主体内容。
10. long getSize()
返回上传文件的大小。
四、备注
1. 在表单里加了 ENCTYPE="multipart/form-data" ,直接用request.getParameter( "name "); 是取不到值的。因为common-fileupload又将参数值进行了一次封装,所以,直接取是没法取到的。需采用上述代码中获取参数的方法。
2. 相比jspSmartUpload,我觉得common-fileupload有如下的优点:
1) 开源;
2) Jakarta项目组的支持,开发十分活跃,而 jspSmartUpload 则已经停止开发了;
3) 不需要写入文件之前即可获取到参数和文件信息,jspSmartUpload 则需要在获取之前调用 upload 方法;
4) 对中文支持友好。
参考文档:使用common-fileupload.jar实现文件上传
转载请注明:观测者 » 使用common-fileupload实现文件上传