6.6开发社区搜索功能

业务层：新建ElasticsearchService类

package com.nowcoder.community.service;

import com.nowcoder.community.dao.elasticsearch.DiscussPostRepository;
import com.nowcoder.community.entity.DiscussPost;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.search.SearchHit;
import org.elasticsearch.search.SearchHits;
import org.elasticsearch.search.fetch.subphase.highlight.HighlightBuilder;
import org.elasticsearch.search.fetch.subphase.highlight.HighlightField;
import org.elasticsearch.search.sort.SortBuilders;
import org.elasticsearch.search.sort.SortOrder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.elasticsearch.core.ElasticsearchTemplate;
import org.springframework.data.elasticsearch.core.SearchResultMapper;
import org.springframework.data.elasticsearch.core.aggregation.AggregatedPage;
import org.springframework.data.elasticsearch.core.aggregation.impl.AggregatedPageImpl;
import org.springframework.data.elasticsearch.core.query.NativeSearchQueryBuilder;
import org.springframework.data.elasticsearch.core.query.SearchQuery;
import org.springframework.stereotype.Service;

import java.util.ArrayList;
import java.util.Date;
import java.util.List;

@Service
public class ElasticsearchService {
//注入需要用到的bean
    @Autowired
    private DiscussPostRepository discussRepository;

    @Autowired
    private ElasticsearchTemplate elasticTemplate;//用于高亮显示

    public void saveDiscussPost(DiscussPost post) {
        discussRepository.save(post);
    }//传入帖子数据post，

    public void deleteDiscussPost(int id) {
        discussRepository.deleteById(id);
    }

    public Page<DiscussPost> searchDiscussPost(String keyword, int current, int limit) {//搜索到的结果是Page， <DiscussPost>表明里面封装了多条帖子；current表明当前是第几页。
        SearchQuery searchQuery = new NativeSearchQueryBuilder()//构造查询的对象searchQuery
                .withQuery(QueryBuilders.multiMatchQuery(keyword, "title", "content"))
                .withSort(SortBuilders.fieldSort("type").order(SortOrder.DESC))//先按类型排序
                .withSort(SortBuilders.fieldSort("score").order(SortOrder.DESC))//类型一致按分数排序
                .withSort(SortBuilders.fieldSort("createTime").order(SortOrder.DESC))//分数一致按创建时间排序
                .withPageable(PageRequest.of(current, limit))
                .withHighlightFields(
                        new HighlightBuilder.Field("title").preTags("<em>").postTags("</em>"),
                        new HighlightBuilder.Field("content").preTags("<em>").postTags("</em>")
                ).build();

        return elasticTemplate.queryForPage(searchQuery, DiscussPost.class, new SearchResultMapper() {
            @Override
            public <T> AggregatedPage<T> mapResults(SearchResponse response, Class<T> aClass, Pageable pageable) {
                SearchHits hits = response.getHits();
                if (hits.getTotalHits() <= 0) {
                    return null;
                }

                List<DiscussPost> list = new ArrayList<>();
                for (SearchHit hit : hits) {
                    DiscussPost post = new DiscussPost();

                    String id = hit.getSourceAsMap().get("id").toString();
                    post.setId(Integer.valueOf(id));

                    String userId = hit.getSourceAsMap().get("userId").toString();
                    post.setUserId(Integer.valueOf(userId));

                    String title = hit.getSourceAsMap().get("title").toString();
                    post.setTitle(title);

                    String content = hit.getSourceAsMap().get("content").toString();
                    post.setContent(content);

                    String status = hit.getSourceAsMap().get("status").toString();
                    post.setStatus(Integer.valueOf(status));

                    String createTime = hit.getSourceAsMap().get("createTime").toString();
                    post.setCreateTime(new Date(Long.valueOf(createTime)));

                    String commentCount = hit.getSourceAsMap().get("commentCount").toString();
                    post.setCommentCount(Integer.valueOf(commentCount));

                    // 处理高亮显示的结果
                    HighlightField titleField = hit.getHighlightFields().get("title");
                    if (titleField != null) {
                        post.setTitle(titleField.getFragments()[0].toString());
                    }

                    HighlightField contentField = hit.getHighlightFields().get("content");
                    if (contentField != null) {
                        post.setContent(contentField.getFragments()[0].toString());
                    }

                    list.add(post);
                }

                return new AggregatedPageImpl(list, pageable,
                        hits.getTotalHits(), response.getAggregations(), response.getScrollId(), hits.getMaxScore());
            }
        });
    }

}

表现层：将帖子用异步的方式提交到es服务器

在CommunityConstant中定义发帖常量

/**
 * 主题: 发帖
 */
String TOPIC_PUBLISH = "publish";

在DiscussPostController中

// 触发发帖事件，把新发布的帖子存到es服务器
Event event = new Event()
        .setTopic(TOPIC_PUBLISH)//主题：发帖
        .setUserId(user.getId())//是谁触发了事件
        .setEntityType(ENTITY_TYPE_POST)
        .setEntityId(post.getId());
eventProducer.fireEvent(event);//触发事件

评论帖子以后，会修改帖子评论数量，相当于改了帖子。

发布评论：在CommentController中，添加：

// 触发评论事件
Event event = new Event()
        .setTopic(TOPIC_COMMENT)
        .setUserId(hostHolder.getUser().getId())
        .setEntityType(comment.getEntityType())
        .setEntityId(comment.getEntityId())
        .setData("postId", discussPostId);
if (comment.getEntityType() == ENTITY_TYPE_POST) {
    DiscussPost target = discussPostService.findDiscussPostById(comment.getEntityId());
    event.setEntityUserId(target.getUserId());
} else if (comment.getEntityType() == ENTITY_TYPE_COMMENT) {
    Comment target = commentService.findCommentById(comment.getEntityId());
    event.setEntityUserId(target.getUserId());
}
eventProducer.fireEvent(event);

if (comment.getEntityType() == ENTITY_TYPE_POST) {//评论可以给帖子，也可以给评论回复，只有评论给帖子的时候，才能// 触发发帖事件

    event = new Event()
            .setTopic(TOPIC_PUBLISH)
            .setUserId(comment.getUserId())
            .setEntityType(ENTITY_TYPE_POST)
            .setEntityId(discussPostId);
    eventProducer.fireEvent(event);
}

在EventConsumer中

// 消费发帖事件
@KafkaListener(topics = {TOPIC_PUBLISH})
public void handlePublishMessage(ConsumerRecord record) {//消费发帖消息
    if (record == null || record.value() == null) {//得到的消费发帖消息 为空
        logger.error("消息的内容为空!");
        return;
    }

    Event event = JSONObject.parseObject(record.value().toString(), Event.class);
    if (event == null) {
        logger.error("消息格式错误!");
        return;
    }

    DiscussPost post = discussPostService.findDiscussPostById(event.getEntityId());//得到帖子数据
    elasticsearchService.saveDiscussPost(post);//存入服务器
}

新建SearchController

package com.nowcoder.community.controller;

import com.nowcoder.community.entity.DiscussPost;
import com.nowcoder.community.entity.Page;
import com.nowcoder.community.service.ElasticsearchService;
import com.nowcoder.community.service.LikeService;
import com.nowcoder.community.service.UserService;
import com.nowcoder.community.util.CommunityConstant;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@Controller
public class SearchController implements CommunityConstant {

    @Autowired
    private ElasticsearchService elasticsearchService;//查询功能 必然要用到Elasticsearch功能

    @Autowired
    private UserService userService;//搜到帖子以后，还要展示帖子的作者。

    @Autowired
    private LikeService likeService;//展示帖子被点赞的数量

    // search?keyword=xxx
    @RequestMapping(path = "/search", method = RequestMethod.GET)//查询数据，请求方式设置为GET
    public String search(String keyword, Page page, Model model) {
        // 实现搜索帖子
        org.springframework.data.domain.Page<DiscussPost> searchResult =//搜索的结果 是个Page对象。前面这些org.springframework.data.domain.是包名，Page对象里封装的是实体类型，得到搜索结果searchResult
                elasticsearchService.searchDiscussPost(keyword, page.getCurrent() - 1, page.getLimit());//page.getLimit()指每页显示多少条数据
        // 聚合数据
        List<Map<String, Object>> discussPosts = new ArrayList<>();//最终聚合结果是一个List集合
        if (searchResult != null) {
            for (DiscussPost post : searchResult) {//遍历Result ，得到每一个帖子
                Map<String, Object> map = new HashMap<>();
                // 帖子
                map.put("post", post);
                // 作者
                map.put("user", userService.findUserById(post.getUserId()));
                // 点赞数量
                map.put("likeCount", likeService.findEntityLikeCount(ENTITY_TYPE_POST, post.getId()));

                discussPosts.add(map);
            }
        }
        model.addAttribute("discussPosts", discussPosts);
        model.addAttribute("keyword", keyword);

        // 分页信息
        page.setPath("/search?keyword=" + keyword);
        page.setRows(searchResult == null ? 0 : (int) searchResult.getTotalElements());

        return "/site/search";
    }

}

最后写HML，在index首页上对搜索框进行处理

search.html

测试：

访问首页：

搜索：

搜索到：

只列出第一段匹配内容

换个搜索关键字：

登录，发布新帖子


搜索：

针对头像过大的问题，我们把宽和高进行设置

<img th:src="${map.user.headerUrl}" class="mr-4 rounded-circle" alt="用户头像" style="width:50px;height:50px;"><!--头像 -->

本节课利用elastic search结合之前所学的 消息队列，把搜索功能实现，