java图片请求

❶ java 中如何向服务器上传图片

我们使用一些已有的组件帮助我们实现这种上传功能。
常用的上传组件：
Apache 的 Commons FileUpload
JavaZoom的UploadBean
jspSmartUpload
以下，以FileUpload为例讲解
1、在jsp端
<form id="form1" name="form1" method="post" action="servlet/fileServlet" enctype="multipart/form-data">
要注意enctype="multipart/form-data"
然后只需要放置一个file控件，并执行submit操作即可
<input name="file" type="file" size="20" >
<input type="submit" name="submit" value="提交" >
2、web端
核心代码如下：
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
DiskFileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(factory);
try {
List items = upload.parseRequest(request);
Iterator itr = items.iterator();
while (itr.hasNext()) {
FileItem item = (FileItem) itr.next();
if (item.isFormField()) {
System.out.println("表单参数名:" + item.getFieldName() + "，表单参数值:" + item.getString("UTF-8"));
} else {
if (item.getName() != null && !item.getName().equals("")) {
System.out.println("上传文件的大小:" + item.getSize());
System.out.println("上传文件的类型:" + item.getContentType());
System.out.println("上传文件的名称:" + item.getName());
File tempFile = new File(item.getName());
File file = new File(sc.getRealPath("/") + savePath, tempFile.getName());
item.write(file);
request.setAttribute("upload.message", "上传文件成功！");
}else{
request.setAttribute("upload.message", "没有选择上传文件！");
}
}
}
}catch(FileUploadException e){
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
request.setAttribute("upload.message", "上传文件失败！");
}
request.getRequestDispatcher("/uploadResult.jsp").forward(request, response);
}

❷ java 访问url获取图片

private static final String imgDir="C:/Program Files/Tencent/TM2009/Users/273367058/FileRecv";//这里填上图片目录全名就行了
static{
try{
File dir = new File(imgDir);
File[] imgFiles = dir.listFiles(new FilenameFilter(){
public boolean accept(File dir, String name) {
return name.toLowerCase().endsWith(".jpg");
}
});

❸ 用java怎么读取图片

思路：使用 java.awt.Image包下的Image可以接收图片。读取则使用ImageIO对象。

代码如下：

/**
* 读取图片，首先导入以下的包
*/
import java.awt.Image;
import javax.imageio.ImageIO;
import java.io.*;

/**
* 用Image对象来接收图片
* 路径根据实际情况修改
*/
Image image = ImageIO.read(new File("c:\\1.png"));
System.out.println(image.getSource());

❹ java爬虫读取某一张指定图片的url，求解答

使用jsoup解析到这个url就行，dom结构如下:

❺ 怎么用Java实现图片上传

下面这是servlet的内容：
package demo;

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.ProgressListener;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

public class DemoServlet extends HttpServlet {

private static final String UPLOAD_DIRECTORY = "upload";
private static final int MEMORY_THRESHOLD = 1024 * 1024 * 3; // 3MB
private static final int MAX_FILE_SIZE = 1024 * 1024 * 40; // 40MB
private static final int MAX_REQUEST_SIZE = 1024 * 1024 * 50; // 50MB

protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
DiskFileItemFactory factory=new DiskFileItemFactory();
ServletFileUpload sfu=new ServletFileUpload(factory);
sfu.setHeaderEncoding("UTF-8");
sfu.setProgressListener(new ProgressListener() {

public void update(long pBytesRead, long pContentLength, int pItems) {
System.out.println("文件大小为："+pContentLength+",当前已处理："+pBytesRead);

}
});
//判断提交上来的数据是否是上传表单的数据
if(!ServletFileUpload.isMultipartContent(request)){
PrintWriter writer= response.getWriter();
writer.println("Error:表单必须包含 enctype=multipart/form-data");
writer.flush();
return;
}
factory.setSizeThreshold(MEMORY_THRESHOLD);
//设置临时储存目录
factory.setRepository(new File(System.getProperty("java.io.tmpdir")));
//设置最大文件上传值
sfu.setFileSizeMax(MAX_FILE_SIZE);
//设置最大请求值（包含文件和表单数据）
sfu.setSizeMax(MAX_REQUEST_SIZE);
String uploadpath=getServletContext().getRealPath("./")+ File.separator+UPLOAD_DIRECTORY;
File file=new File(uploadpath);
if(!file.exists()){
file.mkdir();
}

try {
List<FileItem> formItems = sfu.parseRequest(request);
if(formItems!=null&&formItems.size()>0){
for(FileItem item:formItems){
if(!item.isFormField()){
String fileName=new File(item.getName()).getName();
String filePath=uploadpath+File.separator+fileName;
File storeFile=new File(filePath);
System.out.println(filePath);
item.write(storeFile);
request.setAttribute("message", "文件上传成功！");
}
}
}
} catch (Exception e) {
request.setAttribute("message", "错误信息："+e.getMessage());
}
getServletContext().getRequestDispatcher("/demo.jsp").forward(request, response);
}

}

下面是jsp的内容，jsp放到webapp下，如果想放到WEB-INF下就把servlet里转发的路径改一下：
<%@ 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="demo.do" enctype="multipart/form-data" method="post">
<input type="file" name="file1" />
<%
String message = (String) request.getAttribute("message");
%>
<%=message%>
<input type="submit" value="提交"/>
</form>
</body>
</html>
这段代码可以实现普通的文件上传，有大小限制，上传普通的图片肯定没问题，别的一些小的文件也能传