帮我设计一个基于ssm框架的留言功能，包含留言和回复两张表，回复不限制层级。要求包含mybatis层到dao层再到controller层实例说明

好的，基于SSM框架的留言功能的设计和实现步骤如下：

1. 创建Maven项目，引入Spring、SpringMVC和MyBatis的相关依赖。

2. 在web.xml中配置DispatcherServlet，并指定SpringMVC的配置文件位置。

<servlet>
    <servlet-name>dispatcherServlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:spring-mvc.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
    <servlet-name>dispatcherServlet</servlet-name>
    <url-pattern>/</url-pattern>
</servlet-mapping>

3. 在SpringMVC配置文件中开启组件扫描和注解驱动，并配置视图解析器。

<context:component-scan base-package="com.example.controller" />

<mvc:annotation-driven />

<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix" value="/WEB-INF/views/" />
    <property name="suffix" value=".jsp" />
</bean>

4. 创建数据库，并在MyBatis中配置数据源和SQL映射文件。

<dataSource type="POOLED">
    <property name="driver" value="${jdbc.driverClassName}" />
    <property name="url" value="${jdbc.url}" />
    <property name="username" value="${jdbc.username}" />
    <property name="password" value="${jdbc.password}" />
</dataSource>

<mapper namespace="com.example.dao.MessageDao">
    <select id="findAllMessages" resultType="com.example.entity.Message">
        SELECT * FROM message
    </select>
</mapper>

<mapper namespace="com.example.dao.ReplyDao">
    <select id="findAllReplies" resultType="com.example.entity.Reply">
        SELECT * FROM reply
    </select>
</mapper>

5. 创建实体类Message和Reply，用于映射数据库中的表和字段。

public class Message {
    private int id;
    private String content;
    private Date createTime;
    private Date updateTime;
    private List<Reply> replies;
    // 省略getter和setter方法
}

public class Reply {
    private int id;
    private int messageId;
    private String content;
    private int parentId;
    private Date createTime;
    private Date updateTime;
    private List<Reply> replies;
    // 省略getter和setter方法
}

6. 创建DAO层接口MessageDao和ReplyDao，并在MyBatis中配置对应的SQL映射。

public interface MessageDao {
    List<Message> findAllMessages();
}

public interface ReplyDao {
    List<Reply> findAllReplies();
}

7. 创建Service层接口MessageService和ReplyService，并注入DAO层依赖，实现查询所有留言和所有回复的方法。

public interface MessageService {
    List<Message> findAllMessages();
}

@Service
public class MessageServiceImpl implements MessageService {

    @Autowired
    private MessageDao messageDao;

    @Override
    public List<Message> findAllMessages() {
        List<Message> messages = messageDao.findAllMessages();
        for (Message message : messages) {
            List<Reply> replies = messageDao.findRepliesByMessageId(message.getId());
            message.setReplies(replies);
        }
        return messages;
    }
}

public interface ReplyService {
    List<Reply> findAllReplies();
}

@Service
public class ReplyServiceImpl implements ReplyService {

    @Autowired
    private ReplyDao replyDao;

    @Override
    public List<Reply> findAllReplies() {
        List<Reply> replies = replyDao.findAllReplies();
        for (Reply reply : replies) {
            List<Reply> subReplies = replyDao.findSubRepliesByParentId(reply.getId());
            reply.setReplies(subReplies);
        }
        return replies;
    }
}

8. 创建Controller层，并注入Service层依赖，实现查询所有留言和所有回复的接口。

@Controller
@RequestMapping("/message")
public class MessageController {

    @Autowired
    private MessageService messageService;

    @RequestMapping("/findAll")
    public ModelAndView findAll() {
        List<Message> messages = messageService.findAllMessages();
        ModelAndView mav = new ModelAndView("message");
        mav.addObject("messages", messages);
        return mav;
    }
}

@Controller
@RequestMapping("/reply")
public class ReplyController {

    @Autowired
    private ReplyService replyService;

    @RequestMapping("/findAll")
    public ModelAndView findAll() {
        List<Reply> replies = replyService.findAllReplies();
        ModelAndView mav = new ModelAndView("reply");
        mav.addObject("replies", replies);
        return mav;
    }
}

9. 在jsp页面中展示查询结果。

<!-- message.jsp -->
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>留言列表</title>
</head>
<body>
    <h1>留言列表</h1>
    <table>
        <thead>
            <tr>
                <th>ID</th>
                <th>内容</th>
                <th>创建时间</th>
                <th>更新时间</th>
            </tr>
        </thead>
        <tbody>
            <c:forEach items="${messages}" var="message">
                <tr>
                    <td>${message.id}</td>
                    <td>${message.content}</td>
                    <td>${message.createTime}</td>
                    <td>${message.updateTime}</td>
                </tr>
                <c:forEach items="${message.replies}" var="reply">
                    <tr>
                        <td>${reply.id}</td>
                        <td>${reply.content}</td>
                        <td>${reply.createTime}</td>
                        <td>${reply.updateTime}</td>
                    </tr>
                    <c:forEach items="${reply.replies}" var="subReply">
                        <tr>
                            <td>${subReply.id}</td>
                            <td>${subReply.content}</td>
                            <td>${subReply.createTime}</td>
                            <td>${subReply.updateTime}</td>
                        </tr>
                    </c:forEach>
                </c:forEach>
            </c:forEach>
        </tbody>
    </table>
</body>
</html>

<!-- reply.jsp -->
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>回复列表</title>
</head>
<body>
    <h1>回复列表</h1>
    <table>
        <thead>
            <tr>
                <th>ID</th>
                <th>留言ID</th>
                <th>内容</th>
                <th>父级回复ID</th>
                <th>创建时间</th>
                <th>更新时间</th>
            </tr>
        </thead>
        <tbody>
            <c:forEach items="${replies}" var="reply">
                <tr>
                    <td>${reply.id}</td>
                    <td>${reply.messageId}</td>
                    <td>${reply.content}</td>
                    <td>${reply.parentId}</td>
                    <td>${reply.createTime}</td>
                    <td>${reply.updateTime}</td>
                </tr>
                <c:forEach items="${reply.replies}" var="subReply">
                    <tr>
                        <td>${subReply.id}</td>
                        <td>${subReply.messageId}</td>
                        <td>${subReply.content}</td>
                        <td>${subReply.parentId}</td>
                        <td>${subReply.createTime}</td>
                        <td>${subReply.updateTime}</td>
                    </tr>
                    <c:forEach items="${subReply.replies}" var="subSubReply">
                        <tr>
                            <td>${subSubReply.id}</td>
                            <td>${subSubReply.messageId}</td>
                            <td>${subSubReply.content}</td>
                            <td>${subSubReply.parentId}</td>
                            <td>${subSubReply.createTime}</td>
                            <td>${subSubReply.updateTime}</td>
                        </tr>
                    </c:forEach>
                </c:forEach>
            </c:forEach>
        </tbody>
    </table>
</body>
</html>

至此，我们完成了基于SSM框架的留言功能的设计和实现。对于查询所有留言和所有回复的接口，我们可以通过访问以下URL进行访问：

- 查询所有留言：http://localhost:8080/message/findAll
- 查询所有回复：http://localhost:8080/reply/findAll