7. List of private messages

1、创建Message实体类

@Data
@AllArgsConstructor
@NoArgsConstructor
public class  Message {
    
    private int id;
    private int fromId;
    private int toId;
    private String conversationId;
    private String content;
    private int status;
    private Date createTime;
}

2、数据访问层MessageMapper

@Mapper
public interface MessageMapper {
    

    // 查询当前用户的会话列表,针对每个会话只返回一条最新的私信.
    List<Message> selectConversations(int userId, int offset, int limit);

    // 查询当前用户的会话数量.
    int selectConversationCount(int userId);

    // 查询某个会话所包含的私信列表.
    List<Message> selectLetters(String conversationId, int offset, int limit);

    // 查询某个会话所包含的私信数量.
    int selectLetterCount(String conversationId);

    // 查询未读私信的数量
    int selectLetterUnreadCount(int userId, String conversationId);
    
}

message-mapper.xml

<mapper namespace="com.nowcoder.community.dao.MessageMapper">
    <sql id="selectFields">
        id, from_id, to_id, conversation_id, content, status, create_time
    </sql>


<!--    // 查询当前用户的会话列表,针对每个会话只返回一条最新的私信.-->
<!--    List<Message> selectConversations(int userId, int offset, int limit);-->
    <select id="selectConversations" resultType="Message">
        select <include refid="selectFields"></include>
        from message
        where id in(
            select max(id) from message
            where status != 2
            and from_id != 1
            and (from_id = #{
    userId} or to_id = #{
    userId})
            group by conversation_id
        )
        order by id desc
        limit #{
    offset}, #{
    limit}
    </select>

<!--    // 查询当前用户的会话数量.-->
<!--    int selectConversationCount(int userId);-->
    <select id="selectConversationCount" resultType="int">
        select count(m.maxid) from(
            select max(id) as maxid from message
            where status != 2
            and from_id != 1
            and (from_id = #{
    userId} or to_id = #{
    userId})
            group by conversation_id
        ) as m
    </select>

<!--    // 查询某个会话所包含的私信列表.-->
<!--    List<Message> selectLetters(String conversationId, int offset, int limit);-->
    <select id="selectLetters" resultType="Message">
        select <include refid="selectFields"></include>
        from message
        where status != 2
        and from_id != 1
        and conversation_id = #{
    conversationId}
        order by id desc
        limit #{
    offset}, #{
    limit}
    </select>


<!--    // 查询某个会话所包含的私信数量.-->
<!--    int selectLetterCount(String conversationId);-->
    <select id="selectLetterCount" resultType="int">
        select count(id)
        from message
        where status != 2
        and from_id != 1
        and conversation_id = #{
    conversationId}
    </select>

<!--    // 查询未读私信的数量-->
<!--    int selectLetterUnreadCount(int userId, String conversationId);-->
    <select id="selectLetterUnreadCount" resultType="int">
        select count(id)
        from message
        where status = 0
        and from_id != 1
        and to_id = #{
    userId}
        <if test="conversationId != null">
            and conversation_id = #{
    conversationId}
        </if>
    </select>
    
</mapper>

3、业务层

@Service
public class MessageService {
    
    
    @Autowired
    private MessageMapper messageMapper;

    public List<Message> findConversations(int userId, int offset, int limit) {
    
        return messageMapper.selectConversations(userId, offset, limit);
    }

    public int findConversationCount(int userId) {
    
        return messageMapper.selectConversationCount(userId);
    }

    public List<Message> findLetters(String conversationId, int offset, int limit) {
    
        return messageMapper.selectLetters(conversationId, offset, limit);
    }

    public int findLetterCount(String conversationId) {
    
        return messageMapper.selectLetterCount(conversationId);
    }

    public int findLetterUnreadCount(int userId, String conversationId) {
    
        return messageMapper.selectLetterUnreadCount(userId, conversationId);
    }
}

4、表现层

@Controller
public class MessageController implements CommunityConstant {
    

    @Autowired
    private MessageService messageService;

    @Autowired
    private HostHolder hostHolder;

    @Autowired
    private UserService userService;

    // 私信列表
    @GetMapping("/letter/list")
    public String getLetterList(Model model, Page page) {
    

        User user = hostHolder.getUser();
        // 分页信息
        page.setLimit(5);
        page.setPath("/letter/list");
        page.setRows(messageService.findConversationCount(user.getId()));
        // 会话列表
        List<Message> conversationList =
                messageService.findConversations(user.getId(), page.getOffset(), page.getLimit());
        List<Map<String, Object>> conversations = new ArrayList<>();
        if (conversationList != null) {
    
            for (Message message : conversationList) {
    
                Map<String, Object> map = new HashMap<>(16);
                map.put("conversation", message);
                map.put("letterCount", messageService.findLetterCount(message.getConversationId()));
                map.put(
                        "unreadCount",
                        messageService.findLetterUnreadCount(
                                user.getId(), message.getConversationId()));
                int targetId =
                        user.getId() == message.getFromId()
                                ? message.getToId()
                                : message.getFromId();
                map.put("target", userService.findUserById(targetId));
                conversations.add(map);
            }
        }
        model.addAttribute("conversations", conversations);
        // 查询未读消息数量
        int letterUnreadCount = messageService.findLetterUnreadCount(user.getId(), null);
        model.addAttribute("letterUnreadCount", letterUnreadCount);
        int noticeUnreadCount =
                messageService.findNoticeUnreadCount(hostHolder.getUser().getId(), null);
        model.addAttribute("noticeUnreadCount", noticeUnreadCount);
        return "site/letter";
    }

    // specific personal message
    @GetMapping("/letter/detail/{conversationId}")
    public String getLetterDetail(
            @PathVariable("conversationId") String conversationId, Page page, Model model) {
    
        // 分页信息
        page.setLimit(5);
        page.setPath("/letter/detail/" + conversationId);
        page.setRows(messageService.findLetterCount(conversationId));

        // 私信列表
        List<Message> letterList =
                messageService.findLetters(conversationId, page.getOffset(), page.getLimit());
        List<Map<String, Object>> letters = new ArrayList<>();
        if (letterList != null) {
    
            for (Message message : letterList) {
    
                Map<String, Object> map = new HashMap<>(16);
                map.put("letter", message);
                map.put("fromUser", userService.findUserById(message.getFromId()));
                letters.add(map);
            }
        }
        model.addAttribute("letters", letters);
        model.addAttribute("letters", letters);
        // 私信目标
        model.addAttribute("target", getLetterTarget(conversationId));

        // 设置已读
        List<Integer> ids = getLetterIds(letterList);
        if (!ids.isEmpty()) {
    
            messageService.readMessage(ids);
        }

        return "site/letter-detail";
    }

    /** * Get all unread messagesid * * @param letterList * @return */
    private List<Integer> getLetterIds(List<Message> letterList) {
    
        List<Integer> ids = new ArrayList<>();
        if (letterList != null) {
    
            for (Message message : letterList) {
    
                if (hostHolder.getUser().getId() == message.getToId() && message.getStatus() == 0) {
    
                    ids.add(message.getId());
                }
            }
        }
        return ids;
    }
}