1.私信功能

①数据库字段

②编写实体类和Mapper

@Data
@ToString
public class Message {

    private int id;
    private int fromId;
    private int toId;
    private String conversationId;
    private String content;
    private int status;
    private Date createTime;
}

@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);

}

③编写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>
    
    <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>

    <select id="selectConversationCount" resultType="int">
        select count(m.maxid) from (
           select max(id) from message
           where status != 2
             and from_id != 1
             and (from_id = #{userId} or to_id = #{userId})
           group by conversation_id
        ) as m
    </select>

    <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>

    <select id="selectLetterCount" resultType="int">
        select count(id)
        from message
        where status != 2
        and from_id != 1
        and conversation_id = #{conversationId}
    </select>

    <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编写MessageService

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

④编写MessageController

@Controller
public class MessageController {

    @Autowired
    private MessageService messageService;

    @Autowired
    private HostHolder hostHolder;

    @Autowired
    private UserService userService;

    //私信列表
    @RequestMapping(path = "/letter/list",method = RequestMethod.GET)
    public String getLetterList(Model model, Page page){
        User user = hostHolder.getUser();
        //设置分页信息
        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<>();
                map.put("conversation",message);
                map.put("letterCount",messageService.findLettersCount(message.getConversationId()));
                map.put("unreadCount",messageService.findLetterUnreadCount(user.getId(),message.getConversationId()));
                int taegetId = user.getId() == message.getFromId() ? message.getToId() : message.getFromId();
                map.put("target",userService.findUserById(taegetId));

                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);

        return "/site/letter";
    }
    @RequestMapping(path = "/letter/detail/{conversationId}", method = RequestMethod.GET)
    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.findLettersCount(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<>();
                map.put("letter", message);
                map.put("fromUser", userService.findUserById(message.getFromId()));
                letters.add(map);
            }
        }
        model.addAttribute("letters", letters);

        // 私信目标
        model.addAttribute("target", getLetterTarget(conversationId));

        return "/site/letter-detail";
    }

    private User getLetterTarget(String conversationId) {
        String[] ids = conversationId.split("_");
        int id0 = Integer.parseInt(ids[0]);
        int id1 = Integer.parseInt(ids[1]);

        if (hostHolder.getUser().getId() == id0) {
            return userService.findUserById(id1);
        } else {
            return userService.findUserById(id0);
        }
    }
}

⑤编写前端页面(略)

2.回复私信功能

①编写InsertMessage方法

<insert id="insertMessage" parameterType="Message" keyProperty="id">
    insert into message (<include refid="insetFields"></include>)
    values (#{fromId},#{toId},#{conversationId},#{content},#{status},#{createTime})
</insert>

<update id="updateStatus">
    update message set status=#{status}
    where id in
    <foreach collection="ids" item="id" open="(" separator="," close=")">
        #{id}
    </foreach>
</update>

②编写MessageService

public int addMessage(Message message){
    message.setContent(HtmlUtils.htmlEscape(message.getContent()));
    message.setContent(sensitiveFilter.filter(message.getContent()));
    return messageMapper.insertMessage(message);
}

public int readMessage(List<Integer> ids){
    return messageMapper.updateStatus(ids,1);
}

③编写Controller

    //获取未读消息ID
    private List<Integer> getLetterIds(List<Message> letterList){
        ArrayList<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;
    }

@RequestMapping(path = "/letter/send",method = RequestMethod.POST)
@ResponseBody
public String sendLetter(String toName,String content){
    User terget = userService.findUserByName(toName);
    if (terget == null){
        return CommunityUtil.getJSONString(1,"目标用户不存在");
    }
    Message message = new Message();
    /**
         * hostHolder.getUser().getId() 获得当前登录用户的id
         */
    message.setFromId(hostHolder.getUser().getId());
    message.setToId(terget.getId());
    if (message.getFromId() < message.getToId()){
        message.setConversationId(message.getFromId() + "_" +message.getToId());
    }else{
        message.setConversationId(message.getToId() + "_" +message.getFromId());
    }
    message.setContent(content);
    message.setCreateTime(new Date());
    messageService.addMessage(message);

    return CommunityUtil.getJSONString(0);
}

④在getLetterDetail方法中添加

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

3.统一异常处理

@ControllerAdvice(annotations = Controller.class)
public class ExceptionAdvice {

    private static final Logger logger = LoggerFactory.getLogger(ExceptionAdvice.class);

    @ExceptionHandler({Exception.class})
    public void handleException(Exception e, HttpServletRequest request, HttpServletResponse response) throws IOException {
        logger.error("服务器发异常"+e.getMessage());
        for (StackTraceElement element : e.getStackTrace()){
            logger.error(element.toString());
        }

        String XRequestedWith = request.getHeader("x-requested-with");
        if ("XMLHttpRequest".equals(XRequestedWith)){
            response.setContentType("application/plain;charset=utf-8");
            PrintWriter writer = response.getWriter();
            writer.write(CommunityUtil.getJSONString(1,"服务器异常"));
        }else{
            response.sendRedirect(request.getContextPath() + "/error");
        }

    }
}

4.统一记录日志

target指目标对象，

①测试代码

@Component
@Aspect
public class AlphaAspect {

    @Pointcut("execution(* com.nowcoder..community.service.*.*(..))")
    private void pointcut(){

    }

    @Before("pointcut()")
    public void before(){
        System.out.println("before");
    }

    @Before("pointcut()")
    public void after(){
        System.out.println("after");
    }

    @AfterReturning("pointcut()")
    public void AfterReturning(){
        System.out.println("AfterReturning");
    }

    @AfterThrowing("pointcut()")
    public void AfterThrowing(){
        System.out.println("AfterThrowing");
    }

    @Around("pointcut()")
    public Object Around(ProceedingJoinPoint joinPoint) throws Throwable{
        System.out.println("around before");
        Object obj = joinPoint.proceed();
        System.out.println("around after");
        return obj;
    }
}

②记录用户访问

编写织入类

@Component
@Aspect
public class ServiceLogAspect {
    private static final Logger logger = LoggerFactory.getLogger(ServiceLogAspect.class);

    @Pointcut("execution(* com.nowcoder.community.service.*.*(..))")
    public void pointcut(){

    }

    @Before("pointcut()")
    public void before(JoinPoint joinPoint){
        //用户[1.2.3.4],在[xxx],访问了[com.nowcoder.community.service.xxx[]]
        ServletRequestAttributes attributes = (ServletRequestAttributes)RequestContextHolder.getRequestAttributes();
        HttpServletRequest request = attributes.getRequest();
        String ip = request.getRemoteHost();
        String now = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());

        String target = joinPoint.getSignature().getDeclaringTypeName()+"."+joinPoint.getSignature().getName();
        logger.info(String.format("用户[%s],在[%s],访问了[%s].",ip,now,target));
    }
}

Q.E.D.