【Java Web】使用ajax在论坛中发布帖子

• AJAX
  • 异步的JavaScript与XML，不是一门新技术，只是一个新术语；
  • 使用AJAX，网页能增量更新在页面上，不需要刷新整个页面；
  • JSON的使用比XML使用更加普遍；
• 示例
  • 使用jQuery发送AJAX请求；
• 实践
  • 采用AJAX请求，实现发布帖子功能。

1. DiscussPost类

package com.nowcoder.community.entity;

import java.util.Date;

public class DiscussPost {

    private int id;
    private int userId;
    private String title;
    private String content;
    private int type;
    private int status;
    private Date createTime;
    private int commentCount;
    private double score;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public int getType() {
        return type;
    }

    public void setType(int type) {
        this.type = type;
    }

    public int getStatus() {
        return status;
    }

    public void setStatus(int status) {
        this.status = status;
    }

    public Date getCreateTime() {
        return createTime;
    }

    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }

    public int getCommentCount() {
        return commentCount;
    }

    public void setCommentCount(int commentCount) {
        this.commentCount = commentCount;
    }

    public double getScore() {
        return score;
    }

    public void setScore(double score) {
        this.score = score;
    }

    @Override
    public String toString() {
        return "DiscussPost{" +
                "id=" + id +
                ", userId=" + userId +
                ", title='" + title + '\'' +
                ", content='" + content + '\'' +
                ", type=" + type +
                ", status=" + status +
                ", createTime=" + createTime +
                ", commentCount=" + commentCount +
                ", score=" + score +
                '}';
    }
}

2. mapper

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.nowcoder.community.dao.DiscussPostMapper">

    <sql id="selectFields">
        id, user_id, title, content, type, status, create_time, comment_count, score
    </sql>

    <sql id="insertFields">
        user_id, title, content, type, status, create_time, comment_count, score
    </sql>

    <select id="selectDiscussPosts" resultType="DiscussPost">
        select <include refid="selectFields"></include>
        from discuss_post
        where status != 2
        <if test="userId!=0">
            and user_id = #{userId}
        </if>
        order by type desc, create_time desc
        limit #{offset}, #{limit}
    </select>

    <select id="selectDiscussPostRows" resultType="int">
        select count(id)
        from discuss_post
        where status != 2
        <if test="userId!=0">
            and user_id = #{userId}
        </if>
    </select>

    <insert id="insertDiscussPost" parameterType="DiscussPost">
        insert into discuss_post (<include refid="insertFields"></include>)
        values (#{userId},#{title},#{content},#{type},#{status},#{createTime},#{commentCount},#{score})
    </insert>


</mapper>

3. Service

package com.nowcoder.community.service;

import com.nowcoder.community.dao.DiscussPostMapper;
import com.nowcoder.community.entity.DiscussPost;
import com.nowcoder.community.util.SensitiveFilter;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.util.HtmlUtils;

import java.util.List;

@Service
public class DiscussPostService {

    @Autowired
    private DiscussPostMapper discussPostMapper;

    @Autowired
    private SensitiveFilter sensitiveFilter;

    public List<DiscussPost> findDiscussPosts(int userId, int offset, int limit) {
        return discussPostMapper.selectDiscussPosts(userId, offset, limit);
    }

    public int findDiscussPostRows(int userId) {
        return discussPostMapper.selectDiscussPostRows(userId);
    }

    public int addDiscussPost(DiscussPost post){
        if(post == null){
            throw new IllegalArgumentException("参数不能为空");
        }

        // 转义HTML标记
        post.setTitle(HtmlUtils.htmlEscape(post.getTitle()));
        post.setContent(HtmlUtils.htmlEscape(post.getContent()));
        // 过滤敏感词
        post.setTitle(sensitiveFilter.filter(post.getTitle()));
        post.setContent(sensitiveFilter.filter(post.getContent()));

        return discussPostMapper.insertDiscussPost(post);
    };

}

4. Controller

package com.nowcoder.community.controller;

import com.nowcoder.community.entity.DiscussPost;
import com.nowcoder.community.entity.User;
import com.nowcoder.community.service.DiscussPostService;
import com.nowcoder.community.util.CommunityUtil;
import com.nowcoder.community.util.HostHolder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

import java.util.Date;

@Controller
@RequestMapping(path = "/discuss")
public class DiscussPostController {

    @Autowired
    private DiscussPostService discussPostService;

    @Autowired
    private HostHolder hostHolder;

    @RequestMapping(path="/add", method = RequestMethod.POST)
    @ResponseBody
    public String addDiscussPost(String title, String content){
        User user = hostHolder.getUser();
        if(user == null){  // 未登录
            return CommunityUtil.getJSONString(403,"当前用户未登录！");
        }
        DiscussPost post = new DiscussPost();
        post.setUserId(user.getId());
        System.out.println(user.getId());
        post.setTitle(title);
        post.setContent(content);
        post.setCreateTime(new Date());
        discussPostService.addDiscussPost(post);

        // 报错的情况将来统一处理
        return CommunityUtil.getJSONString(0,"发布成功!");
    }
}

5. 前端jquery

$(function(){
	$("#publishBtn").click(publish);
});

function publish() {
	// 点击“发布”，隐藏发布框
	$("#publishModal").modal("hide");

	// 获取标题和内容
	var title = $("#recipient-name").val();
	var content = $("#message-text").val();

	// 发送异步请求
	$.post(
		CONTEXT_PATH + "/discuss/add",
		{"title":title, "content":content},
		function (data){
			data = $.parseJSON(data);
			// 在提示框中显示返回的消息
			$("#hintBody").text(data.msg);
			// 显示提示框，2秒后自动关闭
			$("#hintModal").modal("show");
			setTimeout(function(){
				$("#hintModal").modal("hide");
				// 刷新页面
				if(data.code == 0){
					window.location.reload();
				}
			}, 2000);
		}
	)


}

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