Ajax實現關鍵字聯想和自動補全功能及遇到坑

2022-08-05 14:02:58

遇到的小坑

回撥函數相對window.onload的擺放位置
給回撥函數addData傳資料時，如何操作才能將資料傳進去

程式碼實現

前端程式碼

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>ajax實現關鍵字聯想和自動補全</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. 給定文字輸入框，顯示層，顯示層裡的顯示欄
            2. 當用戶在文字方塊裡輸入資料時，發生keyup事件時，將文字方塊裡的資料，以ajax請求方式提交的到後端
            3. 後端對前端提交的關鍵字，在資料庫裡進行模糊查詢
            4. 將後端查詢到的資料以json格式傳給前端
            5. 前端解析後端傳來的資料，將資料顯示在提示欄裡
            6. 當用戶點選提示中的某條提示資訊時，將提示欄裡的資訊賦給輸入框，隱藏提示層
            注意：1. 凡是輸入框裡發生keyup事件時，都要進行ajax請求提交，實時獲取提示資訊
                 2. 輸入框資訊為空時，也要隱藏提示層
    -->
    <script>
        window.onload = function (){
            //獲取dom物件
            input_txt = document.getElementById("keyWords")
            div_data = document.getElementById("dataDiv")
            //為輸入框繫結keyup事件
            input_txt.onkeyup = function (){
                //輸入框為空，隱藏提示層
                if(this.value.trim() == ""){
                    div_data.style.display = "none"
                }else{
                    //每當keyup時，傳送ajax請求，傳遞文字方塊內資料
                    var xmlHttpRequest = new XMLHttpRequest();
                    xmlHttpRequest.onreadystatechange = function (){
                        if(this.readyState == 4){
                            if(this.status == 200){
                                //解析後端傳來的json資料:[{"content" : "data"}, {}, {}]
                                var jsonArray = JSON.parse(this.responseText)
                                var html = ""
                                for(var i = 0; i < jsonArray.length; i++){
                                    var perData = jsonArray[i].content
                                    //為p標籤繫結單擊事件,將資料以字串的形式傳給回撥函數
                                    html += "<p onclick='addData(""+perData+"")'>"+perData+"</p>"
                                }
                                div_data.innerHTML = html
                                div_data.style.display = "block"
                            }else{
                                alert("異常狀態碼: " + this.status)
                            }
                        }
                    }
                    xmlHttpRequest.open("GET", "/ajax/ajaxAutoComplete?keyWords="+this.value+"", true)
                    xmlHttpRequest.send()
                }
            }
        }
        function addData(perData){
            //完成自動補全
            input_txt.value= perData
            //隱藏提示層
            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>

後端程式碼

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 {
        //獲取前端傳來的關鍵字
        String keyWords = request.getParameter("keyWords");
        //連線資料庫，進行模糊查詢
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        //封裝關鍵字物件
        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");
                //封裝成關鍵字物件
                KeyWords keyWordsObj = new KeyWords(content);
                //將關鍵字物件封裝
                keyWordsList.add(keyWordsObj);
            }
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }finally {
            DBUtils.close(conn, ps, rs);
        }
        //後端資料json化
        String jsonKeyWordsArray = JSON.toJSONString(keyWordsList);
        //返回後端資料
        response.getWriter().write(jsonKeyWordsArray);
    }
}

用到的實體類

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;
    }
}

自己封裝的jdbc工具類

package com.examples.ajax.utils;
import java.sql.*;
import java.util.ResourceBundle;
/**
 * 封裝自己的jdbc工具類
 */
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);
            }
        }
    }
}