該方式Java中基本上都通用,主要4個步驟,下面的ServletContext對象可以不用,可以根據自己的方式來。
這裏我使用的是SpringMVC,不過它在這裏的唯一用途就是用來獲取ServletContext對象,這個對象的用途,下面實例中有說明
需要用到兩個jar包: commons-fileupload.jar 和 commons-io.jar
代碼如下:
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.context.ServletContextAware;
import javax.servlet.ServletContext;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
@Controller
public class FileController implements ServletContextAware{
//Spring這裏是通過實現ServletContextAware接口來注入ServletContext對象
private ServletContext servletContext;
@Override
public void setServletContext(ServletContext servletContext) {
this.servletContext = servletContext;
}
@RequestMapping("file/download")
public void fileDownload(HttpServletResponse response){
//獲取網站部署路徑(通過ServletContext對象),用於確定下載文件位置,從而實現下載
String path = servletContext.getRealPath("/");
//1.設置文件ContentType類型,這樣設置,會自動判斷下載文件類型
response.setContentType("multipart/form-data");
//2.設置文件頭:最後一個參數是設置下載文件名(假如我們叫zms.jpg,這裏是設置名稱)
response.setHeader("Content-Disposition", "attachment;fileName="+"zms.jpg");
ServletOutputStream out=null;
FileInputStream inputStream=null;
//通過文件路徑獲得File對象(假如此路徑中有一個 zms.jpg 文件)
File file = new File(path + "download/" + "zms.jpg");
try {
inputStream = new FileInputStream(file);
//3.通過response獲取ServletOutputStream對象(out)
out = response.getOutputStream();
int b = 0;
byte[] buffer = new byte[512];
while (b != -1){
b = inputStream.read(buffer);
if(b != -1){
out.write(buffer,0,b);//4.寫到輸出流(out)中
}
}
} catch (IOException e) {
e.printStackTrace();
}finally{
try{
if(inputStream!=null){
inputStream.close();
}
if(out!=null){
out.close();
out.flush();
}
}catch (IOException e) {
e.printStackTrace();
}
}
}
}
第二種方式,直接通過response得到輸出流
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.log4j.Logger;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
@RequestMapping(value="tempDownLoad")
public void tempDownLoad(HttpServletRequest request,HttpServletResponse response){
InputStream in = null;
try{
//1.設置文件ContentType類型,這樣設置,會自動判斷下載文件類型
response.setContentType("multipart/form-data");
//2.設置文件頭:最後一個參數是設置下載文件名
response.setHeader("Content-Disposition", "attachment;fileName=zms.jpg");
//通過文件路徑獲得File對象(假如此路徑中有一個 zms.jpg 文件)
File file = new File("E:/template/zms.jpg");
in = new FileInputStream(file);
//3.通過response獲取ServletOutputStream對象(out)
int b = 0;
byte[] buffer = new byte[512];
while (b != -1){
b = in.read(buffer);
if(b != -1){
response.getOutputStream().write(buffer,0,b);//4.寫到輸出流(out)中
}
}
} catch (Exception e) {
}finally{
try {
if (in != null) {
in.close();
}
response.getOutputStream().flush();
} catch (IOException e) {
e.printStackTrace();
logger.error("關閉文件IOException!");
}
}
}