请求返回json串和文件下载实例

秒速五厘米 2022-07-12 13:17 248阅读 0赞

## 请求返回json串和文件下载实例 ##

### 请求返回json串 ###

JsonServlet代码：

@WebServlet("/JsonServelt")
    public class JsonServelt extends HttpServlet { 
        private static final long serialVersionUID = 1L;
    
    
        public JsonServelt() {
            super();
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //设置编码
            response.setContentType("text/json;charset=utf-8");
            //采用字符集编码方式
            PrintWriter out = response.getWriter();
            //获取json数据
            JSONArray array = MyUtils.getJSONArray();
            //输出json数据
            out.write(array.toString());
    
        }
    
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doGet(request, response);
        }
    
    }

MyUtils类：

public class MyUtils {
        public static JSONArray getJSONArray() {
    
            List<User> listUsers = new ArrayList<>();
    
            listUsers.add(new User("moly",18,2,true,"good kid"));
            listUsers.add( new User("lili",19,3,false,"kid"));
            listUsers.add(new User("lucy",18,2,false,"good kid"));
            listUsers.add(new User("joy",16,2,false,"good kid"));
            listUsers.add(new User("bob",17,2,true,"kid"));
    
            JSONArray array = new JSONArray();
            JSONObject object= null;
    
            for (User user : listUsers) {
                object = new JSONObject();
                try {
                    object.put("name", user.name);
                    object.put("age", user.age);
                    object.put("level", user.level);
                    object.put("sex", user.sex);
                    object.put("desc", user.desc);
                } catch (JSONException e) {
                    e.printStackTrace();
                }
    
                array.put(object);
            }
            return array;
        }
    }

web.xml配置信息

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
        ...
        
        <servlet>
            <servlet-name>JsonServelt</servlet-name>
            <servlet-class>com.yundoku.JsonServelt</servlet-class>
        </servlet>
        <servlet-mapping>
            <servlet-name>JsonServelt</servlet-name>
            <url-pattern>/json</url-pattern>
        </servlet-mapping>
        ...
    </web-app>

--------------------

### 文件下载 ###

DownloadServlet代码：

@WebServlet("/DownloadServlet")
    public class DownloadServlet extends HttpServlet { 
        private static final long serialVersionUID = 1L;
    
        public DownloadServlet() {
            super();
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //设置编码
            response.setContentType("image/jpeg;charset=utf-8");
    
            //获取文件路径
            String realPath = getServletContext().getRealPath("/李冰冰.jpg");
    
            File file = new File(realPath);
    
            //设置下载文件的头信息
            response.setHeader("content-disposition", "attachment;filename="+URLEncoder.encode(file.getName(),"utf-8"));
    
            //创建一个文件字节流
            FileInputStream fis = new FileInputStream(file);
    
            //获取输出流
            ServletOutputStream sos = response.getOutputStream();
    
            //io流操作
            int len = 0;
            byte[] bytes = new byte[1024];
            while((len=fis.read(bytes))>0){
                sos.write(bytes, 0, len);
            }
            //关闭流操作
            sos.flush();
            sos.close();
            fis.close();
    
        }
    
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doGet(request, response);
        }
    
    }

web.xml配置：

<servlet>
        <servlet-name>DownloadServlet</servlet-name>
        <servlet-class>com.yundoku.DownloadServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>DownloadServlet</servlet-name>
        <url-pattern>/download</url-pattern>
    </servlet-mapping>