[Java知识库]牛客网项目——项目开发（五）：私信列表，发送私信，异常处理，记录日志

1. 私信列表

1.1 数据访问层

1.1.1 数据库表

from_id：发送人id
to_id：接收人id
conversation_id：会话id，两人id拼接
status：0-未读;1-已读;2-删除
create_time：创建时间

1.1.2 entity下实现实体类Message

package com.nowcoder.community.entity;

import java.util.Date;

public class Message {

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

    public int getId() {
        return id;
    }

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

    public int getFromId() {
        return fromId;
    }

    public void setFromId(int fromId) {
        this.fromId = fromId;
    }

    public int getToId() {
        return toId;
    }

    public void setToId(int toId) {
        this.toId = toId;
    }

    public String getConversationId() {
        return conversationId;
    }

    public void setConversationId(String conversationId) {
        this.conversationId = conversationId;
    }

    public String getContent() {
        return content;
    }

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

    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;
    }

    @Override
    public String toString() {
        return "Message{" +
                "id=" + id +
                ", fromId=" + fromId +
                ", toId=" + toId +
                ", conversationId='" + conversationId + '\'' +
                ", content='" + content + '\'' +
                ", status=" + status +
                ", createTime=" + createTime +
                '}';
    }
}

1.1.3 dao下实现MessageMapper接口

package com.nowcoder.community.dao;

import com.nowcoder.community.entity.Message;
import org.apache.ibatis.annotations.Mapper;

import java.util.List;

@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);
}

1.1.4 mapper下实现message-mapper.xml

<?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.MessageMapper">

    <sql id="selectFields">
        id, from_id, to_id, conversation_id, content, status, create_time
    </sql>

    <sql id="insertFields">
        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) 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>

    <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>

    <insert id="insertMessage" parameterType="Message" keyProperty="id">
        insert into message(<include refid="insertFields"></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>

</mapper>

1.1.5 测试

@Test
public void testSelectLetters() {
    List<Message> list = messageMapper.selectConversations(111, 0, 20);
    for (Message message : list) {
        System.out.println(message);
    }

    int count = messageMapper.selectConversationCount(111);
    System.out.println(count);

    list = messageMapper.selectLetters("111_112", 0, 10);
    for (Message message : list) {
        System.out.println(message);
    }

    count = messageMapper.selectLetterCount("111_112");
    System.out.println(count);

    count = messageMapper.selectLetterUnreadCount(131, "111_131");
    System.out.println(count);

}

1.2 业务层开发

在service下实现MessageService

package com.nowcoder.community.service;

import com.nowcoder.community.dao.MessageMapper;
import com.nowcoder.community.entity.Message;
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 MessageService {

    @Autowired
    private MessageMapper messageMapper;

    @Autowired
    private SensitiveFilter sensitiveFilter;

    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);
    }

    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);
    }

}

1.3 表现层开发

1.3.1 私信列表

在controller下实现MessageController中的getLetterList：

1. 先设置分页信息
2. 查询会话列表，得到一个集合
3. 声明一个集合封装一个map，多个数据放入map
4. 遍历集合放入map
   1. 放入最新一条消息
   2. 放入消息总数
   3. 放入未读消息
   4. 放入当前对话的另一方的id
5. 最后数据放入model传给模板
6. 查询总的未读消息数量，也放入model

@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();
    // 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.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);

    return "/site/letter";
}

在首页index.html上添加连接连到letter.html

<a class="nav-link position-relative" th:href="@{/letter/list}">消息<span class="badge badge-danger">12</span></a>

处理letter.html：

1. 声明模板

<html lang="en" xmlns:th="http://www.thymeleaf.org">

2. 静态资源引入做处理，最后js做处理

<link rel="stylesheet" th:href="@{/css/global.css}" />
<link rel="stylesheet" th:href="@{/css/letter.css}" />
……
<script th:src="@{/js/global.js}"></script>
<script th:src="@{/js/letter.js}"></script>

3. 复用首页头部

4. “朋友私信“连接，显示未读消息数量

<a class="nav-link position-relative active" th:href="@{/letter/list}">
	朋友私信<span class="badge badge-danger" th:text="${letterUnreadCount}" th:if="${letterUnreadCount!=0}">3</span>
</a>

5. 循环处理li

<li class="media pb-3 pt-3 mb-3 border-bottom position-relative" th:each="map:${conversations}">

6. 每个对话的未读数量

<span class="badge badge-danger" th:text="${map.unreadCount}" th:if="${map.unreadCount!=0}">3</span>

7. 目标用户头像

<img th:src="${map.target.headerUrl}" class="mr-4 rounded-circle user-header" alt="用户头像" >

8. 目标用户名字

<span class="text-success" th:utext="${map.target.username}">落基山脉下的闲人</span>

9. 消息发布时间

<span class="float-right text-muted font-size-12" th:text="${#dates.format(map.conversation.createTime,'yyyy-MM-dd HH:mm:ss')}">2019-04-28 14:13:25</span>

10. 详情页面显示内容为最后一条会话，以及会话包含私信的数量

<div>
	a th:href="@{|/letter/detail/${map.conversation.conversationId}|}" th:utext="${map.conversation.content}">米粉车, 你来吧!</a><
	<ul class="d-inline font-size-12 float-right">
		<li class="d-inline ml-2"><a href="#" class="text-primary">共<i th:text="${map.letterCount}">5</i>条会话</a></li>
	</ul>
</div>

11. 分页逻辑，复用index.html的分页逻辑

<nav class="mt-5" th:replace="index::pagination">
	……
</nav>

1.3.2 私信详情

在MessageController下实现getLetterDetail

1. 设置分页信息
2. 和上面逻辑一样，遍历放入一个map
3. 实现方法getLetterTarget

@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.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<>();
            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));

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

    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);
    }
}

修改letter.html，连接到letter-detail.html
编辑letter-detail.html

1. 开头模板
2. 静态资源和js引入
3. header复用
4. 目标人的名字

<h6><b class="square"></b> 来自 <i class="text-success" th:utext="${target.username}">落基山脉下的闲人</i> 的私信</h6>

5. 遍历私信内容

<li class="media pb-3 pt-3 mb-2" th:each="map:${letters}">

6. 用户头像

<img th:src="${map.fromUser.headerUrl}" class="mr-4 rounded-circle user-header" alt="用户头像" >

7. 用户名和时间

<strong class="mr-auto" th:utext="${map.fromUser.username}">落基山脉下的闲人</strong>
<small th:text="${#dates.format(map.letter.createTime,'yyyy-MM-dd HH:mm:ss')}">2019-04-25 15:49:32</small>

8. 正文

<div class="toast-body" th:utext="${map.letter.content}">
	君不见, 黄河之水天上来, 奔流到海不复回!
</div>

9. 复用首页分页逻辑

<nav class="mt-5" th:replace="index::pagination">
	……
</nav>

10. 返回路径，通过一个js方法back()

<button type="button" class="btn btn-secondary btn-sm" onclick="back();">返回</button>

<script>
	function back() {
		location.href = CONTEXT_PATH + "/letter/list";
	}
</script>

2. 发送私信

2.1 数据访问层

1. MessageMapper下添加新方法

// 新增消息
int insertMessage(Message message);

// 修改消息的状态
int updateStatus(List<Integer> ids, int status);

2. message-mapper.xml下添加新方法

<sql id="insertFields">
    from_id, to_id, conversation_id, content, status, create_time
</sql>

<insert id="insertMessage" parameterType="Message" keyProperty="id">
    insert into message(<include refid="insertFields"></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>

2.2 业务层

MessageService下添加新方法

@Autowired
private SensitiveFilter sensitiveFilter;


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);
}

2.3 视图层

2.3.1 MessageController 新加方法

UserService下添加新方法findUserByName

@RequestMapping(path = "/letter/send", method = RequestMethod.POST)
@ResponseBody
public String sendLetter(String toName, String content) {
    User target = userService.findUserByName(toName);
    if (target == null) {
        return CommunityUtil.getJSONString(1, "目标用户不存在!");
    }

    Message message = new Message();
    message.setFromId(hostHolder.getUser().getId());
    message.setToId(target.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);
}

2.3.2 页面逻辑

1. 发送私信按钮

<button type="button" class="btn btn-primary btn-sm position-absolute rt-0" data-toggle="modal" data-target="#sendModal">发私信</button>

$(function(){
	$("#sendBtn").click(send_letter);
	$(".close").click(delete_msg);
});

function send_letter() {
	$("#sendModal").modal("hide");

	var toName = $("#recipient-name").val();
	var content = $("#message-text").val();
	$.post(
	    CONTEXT_PATH + "/letter/send",
	    {"toName":toName,"content":content},
	    function(data) {
	        data = $.parseJSON(data);
	        if(data.code == 0) {
	            $("#hintBody").text("发送成功!");
	        } else {
	            $("#hintBody").text(data.msg);
	        }

	        $("#hintModal").modal("show");
            setTimeout(function(){
                $("#hintModal").modal("hide");
                location.reload();
            }, 2000);
	    }
	);
}

function delete_msg() {
	// TODO 删除数据
	$(this).parents(".media").remove();
}

2. 发给对话目标

<label for="recipient-name" class="col-form-label">发给：</label>
<input type="text" class="form-control" id="recipient-name" th:value="${target.username}">

MessageController里添加方法设置为已读

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;
}

3. 统一异常处理

3.1 Spring的异常处理

错误页面要放在resources.templates.error下，这样出错后自动跳到错误页面

3.2 @ControllerAdvice

@ExceptionHandler 统一处理异常

1. 在HomeController 里声明方法getErrorPage()错误访问页面

@RequestMapping(path = "/error", method = RequestMethod.GET)
public String getErrorPage() {
    return "/error/500";
}

2. controller下新建包advice新建ExceptionAdvice类
   
3. annotations = Controller.class 表示只扫描Controller这个包下
4. @ExceptionHandler({Exception.class})，修饰的方法表示处理异常的方法，括号内的参数表示处理的错误类型
5. 遍历所有异常信息，记入日志
6. 通过 request.getHeader("x-requested-with");获得请求的方式
7. 如果是异步请求，响应一个Json字符串显示服务器异常
8. 否则响应错误路径

package com.nowcoder.community.controller.advice;

import com.nowcoder.community.util.CommunityUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@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("服务器发生异常: " + 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

4.1 AOP

在业务需求里耦合了系统需求，这样是不好的

1. 目标对象，target
2. 能被织入代码的连接点，joinpoint
3. 方面组件
4. 切点声明切入点
5. Advice声明具体逻辑

4.2 具体实例

在aspect下实现AlphaAspect

1. 加入注解 @Component 和 @Aspect

@Component
@Aspect
public class AlphaAspect {
	……
}

2. 定义切点，注解 @Pointcut

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

}

3. 在连接接点前织入，注解 @Before

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

4. 在连接点后织入，注解 @After

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

5. 在返回值之后，

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

6. 抛异常时

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

7. 前后都织入

@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;
}

4.3 记录用户访问日志

实现 aspect 下的 ServiceLogAspect 类

1. 类注解

@Component
@Aspect

2. 声明切点

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

}

3. 前置通知

@Before("pointcut()")
public void before(JoinPoint joinPoint) {
}

4. RequestContextHolder.getRequestAttributes(); 得到request对象
5. 得到ip地址

String ip = request.getRemoteHost();

6. 得到时间

String now = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());

7. 访问的具体类的方法，使用joinPoint

String target = joinPoint.getSignature().getDeclaringTypeName() + "." + joinPoint.getSignature().getName();

8. 格式化记入日志

// 用户[1.2.3.4],在[xxx],访问了[com.nowcoder.community.service.xxx()].
logger.info(String.format("用户[%s],在[%s],访问了[%s].", ip, now, target));

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