HTTP 下载文件工具类

ResponseUtils.java

package javax.utils;

import java.io.ByteArrayInputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.io.PrintWriter;

import java.net.URLEncoder;

import javax.servlet.http.HttpServletResponse;

import com.fasterxml.jackson.databind.ObjectMapper;

/**

 * HTTP 输出响应内容工具类

 *

 * @author Logan

 * @createDate 2019-02-13

 * @version 1.0.0

 *

 */

public class ResponseUtils {

    /**

     * 发送HTTP响应信息

     *

     * @param response HTTP响应对象

     * @param message 信息内容

     * @throws IOException 抛出异常，由调用者捕获处理

     */

    public static void write(HttpServletResponse response, String message) throws IOException {

        response.setContentType("text/html;charset=UTF-8");

        try (

                PrintWriter writer = response.getWriter();

        ) {

            writer.write(message);

            writer.flush();

        }

    }

    /**

     * 发送HTTP响应信息,JSON格式

     *

     * @param response HTTP响应对象

     * @param message 输出对象

     * @throws IOException 抛出异常，由调用者捕获处理

     */

    public static void write(HttpServletResponse response, Object message) throws IOException {

        response.setContentType("application/json;charset=UTF-8");

        ObjectMapper mapper = new ObjectMapper();

        try (

                PrintWriter writer = response.getWriter();

        ) {

            writer.write(mapper.writeValueAsString(message));

            writer.flush();

        }

    }

    /**

     * 下载文件

     *

     * @param response HTTP响应对象

     * @param file 需要下载的文件

     * @throws IOException 抛出异常，由调用者捕获处理

     */

    public static void download(HttpServletResponse response, File file) throws IOException {

        String fileName = file.getName();

        try (

                FileInputStream in = new FileInputStream(file);

        ) {

            download(response, in, fileName);

        }

    }

    /**

     * 下载文件

     *

     * @param response HTTP响应对象

     * @param data 需要下载的文件二进制内容

     * @param fileName 下载文件名

     * @throws IOException 抛出异常，由调用者捕获处理

     */

    public static void download(HttpServletResponse response, byte[] data, String fileName) throws IOException {

        try (

                ByteArrayInputStream in = new ByteArrayInputStream(data);

        ) {

            download(response, in, fileName);

        }

    }

    /**

     * 下载文件

     *

     * @param response HTTP响应对象

     * @param in 输出流

     * @param fileName 下载文件名

     * @throws IOException 抛出异常，由调用者捕获处理

     */

    public static void download(HttpServletResponse response, InputStream in, String fileName) throws IOException {

        try (

                OutputStream out = response.getOutputStream();

        ) {

            // 对文件名进行URL转义，防止中文乱码

            fileName = URLEncoder.encode(fileName, "UTF-8");

            // 空格用URLEncoder.encode转义后会变成"+"，所以要替换成"%20"，浏览器会解码回空格

            fileName = fileName.replace("+", "%20");

            // "+"用URLEncoder.encode转义后会变成"%2B"，所以要替换成"+"，浏览器不对"+"进行解码

            fileName = fileName.replace("%2B", "+");

            response.setContentType("application/x-msdownload;charset=UTF-8");

            response.setHeader("Content-Disposition", "attachment; filename=" + fileName);

            byte[] bytes = new byte[4096];

            int len = -1;

            while ((len = in.read(bytes)) != -1) {

                out.write(bytes, 0, len);

            }

            out.flush();

        }

    }

}

HTTP 下载文件工具类

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