使用Servlet根据浏览器request的get方法获取值，将磁盘中与之对应的json数据删除的方法

原文链接： https://www.mk2048.com/blog/blog.php?id=h0jkaikjaahj&title=%E4%BD%BF%E7%94%A8Servlet%E6%A0%B9%E6%8D%AE%E6%B5%8F%E8%A7%88%E5%99%A8request%E7%9A%84get%E6%96%B9%E6%B3%95%E8%8E%B7%E5%8F%96%E5%80%BC%EF%BC%8C%E5%B0%86%E7%A3%81%E7%9B%98%E4%B8%AD%E4%B8%8E%E4%B9%8

package com.swift;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;

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

import com.google.gson.Gson;

/**
 * Servlet implementation class DeleteServlet
 */
@WebServlet("/delete")
public class DeleteServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public DeleteServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        response.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        File file=new File("d:/student.json");
        //获取全部学生对象
        List<Student> list=getAllStudent(file);
        System.out.println(list.toString());
        //获取要删除学生姓名
        String name=request.getParameter("name");
        System.out.println(name);
        //从list对象列表中删除匹配姓名的学生对象
        deleteStudentByName(response, list, name);
        System.out.println(list.toString());
        //将删除后的对象列表写入磁盘文件
        StringBuffer sb=new StringBuffer();//将剩下的json信息保存到sb中，不然文件中只能得到最后一个json数据
        Gson gson=new Gson();
        for(Student stu:list) {
            String json=gson.toJson(stu);
            sb.append(json);
            sb.append("\r\n");
        }
        writeToFile(file, sb.toString());
    }

    private void deleteStudentByName(HttpServletResponse response, List<Student> list, String name) throws IOException {
        for(int i=0;i<list.size();i  ) {
            if(list.get(i).getName().equals(name)) {
                list.remove(i);
                response.getWriter().println("You have already delete the name " name);
            }
        }
    }

    private void writeToFile(File file,String json) {
        PrintWriter pw = null;
        try {
            try {
                pw=new PrintWriter(new OutputStreamWriter(new FileOutputStream(file),"utf-8"));
            } catch (UnsupportedEncodingException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            pw.println(json);
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            pw.close();
        }
    }
    
    private List<Student> getAllStudent(File file) throws UnsupportedEncodingException, FileNotFoundException, IOException {
        BufferedReader br=new BufferedReader(new InputStreamReader(new FileInputStream(file),"utf-8"));
        List<Student> list=new ArrayList<Student>();
        String str;
        while((str=br.readLine())!=null) {
            Gson gson=new Gson();
            Student stu=gson.fromJson(str, Student.class);
            list.add(stu);
        }
        br.close();
        return list;
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

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