遇到的小坑
- 回调函数相对window.onload的摆放位置
- 给回调函数addData传数据时，如何操作才能将数据传进去
代码实现
前端代码
ajax实现关键字联想和自动补全
后端代码
package com.examples.ajax.servlet;
import com.alibaba.fastjson.JSON;
import com.examples.ajax.beans.KeyWords;
import com.examples.ajax.utils.DBUtils;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
@WebServlet("/ajaxAutoComplete")
public class AjaxRequest13 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//获取前端传来的关键字
String keyWords = request.getParameter("keyWords");
//连接数据库，进行模糊查询
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
//封装关键字对象
List keyWordsList = new ArrayList();
try {
conn = DBUtils.getConnection();
String sql = "select content from tb_search where content like ?";
ps = conn.prepareStatement(sql);
ps.setString(1, keyWords + "%");
rs = ps.executeQuery();
while(rs.next()){
String content = rs.getString("content");
//封装成关键字对象
KeyWords keyWordsObj = new KeyWords(content);
//将关键字对象封装
keyWordsList.add(keyWordsObj);
}
} catch (SQLException e) {
throw new RuntimeException(e);
}finally {
DBUtils.close(conn, ps, rs);
}
//后端数据json化
String jsonKeyWordsArray = JSON.toJSONString(keyWordsList);
//返回后端数据
response.getWriter().write(jsonKeyWordsArray);
}
}
用到的实体类
package com.examples.ajax.beans;
public class KeyWords {
private String content;
public KeyWords() {
}
public KeyWords(String content) {
this.content = content;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
}
自己封装的jdbc工具类
package com.examples.ajax.utils;
import java.sql.*;
import java.util.ResourceBundle;
/**
* 封装自己的jdbc工具类
*/
public class DBUtils {
static ResourceBundle bundle = ResourceBundle.getBundle("jdbc");
static String driver;
static String url;
static String username;
static String password;
static {
driver = bundle.getString("driver");
url = bundle.getString("url");
username = bundle.getString("username");
password = bundle.getString("password");
try {
Class.forName(driver);
} catch (ClassNotFoundException e) {
throw new RuntimeException(e);
}
}
private DBUtils(){}
public static Connection getConnection() throws SQLException {
return DriverManager.getConnection(url, username, password);
}
public static void close(Connection conn, PreparedStatement ps, ResultSet rs){
if(rs != null){
try {
rs.close();
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
if(ps != null){
try {
ps.close();
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
if(conn != null){
try {
conn.close();
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
}
}
数据库表:
一张表: tb_search
数据表描述: 除了id, 就一个字段 content varchar(255) not null
效果展示:
自己在远程数据库上用docker运行了一个mysql数据库，查询速度比较慢，但演示关键字联想和自动补全功能的测试目的已经达到
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