传过来的blogId值为什么有值为1能成功传回

图一为servlet的代码，在代码里写了条打印blogId的指令只打出1

图23皆为js代码

• 这篇博客: 博客系统 - (servlet总结,前后端分离)中的 BlogDao 部分也许能够解决你的问题, 你可以仔细阅读以下内容或跳转源博客中阅读:
  

• package model;
  
  import java.sql.Connection;
  import java.sql.PreparedStatement;
  import java.sql.ResultSet;
  import java.sql.SQLException;
  import java.util.ArrayList;
  import java.util.List;
  
  //这个类用于去封装博客表的基本操作
  public class BlogDao {
      // 一. 往博客列表里插入一个博客.
      public void insert(Blog blog){
          //JDBC 的基本代码
          Connection connection = null;
          PreparedStatement statement = null;
          try {
              // 1. 和数据库建立连接
              connection = DBUtil.getConnection();
              // 2. 构造 sql 语句
              String sql = "insert into blog values(null,?,?,?,now())";
              statement = connection.prepareStatement(sql);
              statement.setString(1,blog.getTitle());
              statement.setString(2,blog.getContent());
              statement.setInt(3,blog.getUserId());
              // 3. 执行 sql
              statement.executeUpdate();
          } catch (SQLException throwables) {
              throwables.printStackTrace();
          }finally {
              // 4. 关闭资源
              DBUtil.close(connection,statement,null);
          }
      }
  
      //二. 能够获取到博客表中的所有博客的信息(用于博客列表页,注意此处的获取不一定就是 里面的所有内容)
      public List<Blog> selectAll(){
          List<Blog> blogs = new ArrayList<>();
          Connection connection = null;
          PreparedStatement statement = null;
          ResultSet resultSet = null;
          try {
              connection = DBUtil.getConnection();
              //我们想要让最新的排在博客列表最上面
              String sql = "select * from blog order by postTime desc";
              statement = connection.prepareStatement(sql);
              resultSet = statement.executeQuery();
              while(resultSet.next()){
                  Blog blog = new Blog();
                  blog.setBlogId(resultSet.getInt("blogId"));
                  blog.setTitle(resultSet.getString("title"));
                  //这里我们要针对长的内容进行截取
                  String content = resultSet.getString("content");
                  //自己设定长度
                  if(content.length() > 50){
                      content = content.substring(0,50)+"...";
                  }
                  blog.setContent(content);
                  blog.setUserId(resultSet.getShort("userId"));
                  blog.setPostTime(resultSet.getTimestamp("postTime"));
                  blogs.add(blog);
              }
          } catch (SQLException throwables) {
              throwables.printStackTrace();
          }finally {
              DBUtil.close(connection,statement,resultSet);
          }
          return blogs;
      }
  
      //三. 能够根据博客 id 获取到指定的博客内容(用于在博客详情页)
      public Blog selectOne(int blogId){
          Connection connection = null;
          PreparedStatement statement = null;
          ResultSet resultSet = null;
          try {
              connection = DBUtil.getConnection();
              String sql = "select * from blog where blogId = ?";
              statement = connection.prepareStatement(sql);
              statement.setInt(1,blogId);
              resultSet = statement.executeQuery();
              // 这里根据主键来查询的,查到的要么是 0,要么是 1..
              if(resultSet.next()){
                  Blog blog = new Blog();
                  blog.setBlogId(resultSet.getInt("blogId"));
                  blog.setTitle(resultSet.getString("title"));
                  blog.setContent(resultSet.getString("content"));
                  blog.setUserId(resultSet.getShort("userId"));
                  blog.setPostTime(resultSet.getTimestamp("postTime"));
                  return blog;
              }
          } catch (SQLException throwables) {
              throwables.printStackTrace();
          }finally {
              DBUtil.close(connection,statement,resultSet);
          }
          return null;
      }
  
      //四. 从博客列表中,根据博客 id 删除博客
      public void delete(int blogId){
          Connection connection = null;
          PreparedStatement statement = null;
          try {
              connection = DBUtil.getConnection();
              String sql = "delete from blog where blogId = ?";
              statement = connection.prepareStatement(sql);
              statement.setInt(1,blogId);
              statement.executeUpdate();
          } catch (SQLException throwables) {
              throwables.printStackTrace();
          }finally {
              DBUtil.close(connection,statement,null);
          }
      }
  
  
      //五. 修改
      public void update(Blog blog) {
          Connection connection = null;
          PreparedStatement statement = null;
          try {
              // 1. 建立连接
              connection = DBUtil.getConnection();
              // 2. 拼装 SQL 语句
              String sql = "update blog set content = ? ,title = ? where blogId = ?";
              statement = connection.prepareStatement(sql);
              statement.setString(1, blog.getContent());
              statement.setString(2, blog.getTitle());
  
              statement.setInt(3, blog.getBlogId());
              // 3. 执行 SQL 语句
              int ret = statement.executeUpdate();
              if (ret == 1) {
                  System.out.println("编辑成功");
              } else {
                  System.out.println("编辑失败");
              }
          } catch (SQLException e) {
              e.printStackTrace();
          } finally {
              DBUtil.close(connection, statement, null);
          }
      }
  
      //6. 计算个人文章的总数
      public static Integer selectTotal(int userId){
          Connection connection = null;
          PreparedStatement statement = null;
          ResultSet resultSet = null;
          try {
              connection = DBUtil.getConnection();
              String sql = "select count(userId) from blog where userId = ?";
              statement = connection.prepareStatement(sql);
              statement.setInt(1,userId);
              resultSet = statement.executeQuery();
              if(resultSet.next()){
  
              }
              return resultSet.getInt(1);
  
          } catch (SQLException throwables) {
              throwables.printStackTrace();
          }finally {
              DBUtil.close(connection,statement,resultSet);
          }
          return null;
      }
  
      public static void main(String[] args) {
  
          Integer ret1 = selectTotal(2);
          System.out.println(ret1);
          BlogDao blogDao = new BlogDao();
          Blog blog = new Blog();
          blog.setUserId(1);
          blog.setBlogId(1);
          blog.setTitle("hahah");
          blog.setContent("fff");
          blogDao.update(blog);
      }
  }
  
  
  

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