Ajax实现关键字联想和自动补全功能及遇到坑

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

<!DOCTYPE html>
<html lang=\”en\”>
<head>
<meta charset=\”UTF-8\”>
<title>ajax实现关键字联想和自动补全</title>
<style>
*{
margin: 0;
padding: 0;
box-sizing: border-box;
}
#keyWords{
margin-top: 10px;
margin-left: 10px;
width: 300px;
height: 25px;
font-size: 20px;
padding-left: 5px;
}
#dataDiv{
background-color: wheat;
width: 300px;
margin-left: 10px;
display: none;
}
#dataDiv p{
padding-left: 10px;
padding-top: 7px;
padding-bottom: 3px;
cursor: pointer;
}
#dataDiv p:hover{
background-color: cornflowerblue;
color: white;
}
</style>
</head>
<body>
<!–
需求:
1. 给定文本输入框，显示层，显示层里的显示栏
2. 当用户在文本框里输入数据时，发生keyup事件时，将文本框里的数据，以ajax请求方式提交的到后端
3. 后端对前端提交的关键字，在数据库里进行模糊查询
4. 将后端查询到的数据以json格式传给前端
5. 前端解析后端传来的数据，将数据显示在提示栏里
6. 当用户点击提示中的某条提示信息时，将提示栏里的信息赋给输入框，隐藏提示层
注意：1. 凡是输入框里发生keyup事件时，都要进行ajax请求提交，实时获取提示信息
2. 输入框信息为空时，也要隐藏提示层
–>
<script>
window.onload = function (){
//获取dom对象
input_txt = document.getElementById(\”keyWords\”)
div_data = document.getElementById(\”dataDiv\”)
//为输入框绑定keyup事件
input_txt.onkeyup = function (){
//输入框为空，隐藏提示层
if(this.value.trim() == \”\”){
div_data.style.display = \”none\”
}else{
//每当keyup时，发送ajax请求，传递文本框内数据
var xmlHttpRequest = new XMLHttpRequest();
xmlHttpRequest.onreadystatechange = function (){
if(this.readyState == 4){
if(this.status == 200){
//解析后端传来的json数据:[{\”content\” : \”data\”}, {}, {}]
var jsonArray = JSON.parse(this.responseText)
var html = \”\”
for(var i = 0; i < jsonArray.length; i++){
var perData = jsonArray[i].content
//为p标签绑定单击事件,将数据以字符串的形式传给回调函数
html += \”<p onclick=\’addData(\\\”\”+perData+\”\\\”)\’>\”+perData+\”</p>\”
}
div_data.innerHTML = html
div_data.style.display = \”block\”
}else{
alert(\”异常状态码: \” + this.status)
}
}
}
xmlHttpRequest.open(\”GET\”, \”/ajax/ajaxAutoComplete?keyWords=\”+this.value+\”\”, true)
xmlHttpRequest.send()
}
}
}
function addData(perData){
//完成自动补全
input_txt.value= perData
//隐藏提示层
div_data.style.display = \”none\”
}
</script>
<input type=\”text\” id=\”keyWords\”>
<div id=\”dataDiv\”>
<!–
<p>java</p>
<p>jsp</p>
<p>service</p>
<p>servlet</p>
<p>docker</p>
<p>linux</p>
–>
</div>
</body>
</html>

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<KeyWords> 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);
}
}
}
}