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任务过程中遇到下面两个bug

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md5/des

class="cursor-pointer"> 详细描述

java为什么没有尾递归优化，如果想自己实现尾递归优化，应该从哪入手

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1

class="cursor-pointer"> 详细描述

关于restful 风格实现增删改查

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1

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在服务器启动jetty后无法启动

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jetty/tomcat

class="cursor-pointer"> 详细描述

今天在Linux服务器上安装完Jetty后，启动不了服务，显示地址被占用，但是我修改了端口还是不能够启动，请问有师兄遇到这样的情况吗

错误信息如下：
2019-04-26 22:37:43.929:INFO::main: Logging initialized @634ms
2019-04-26 22:37:44.001:WARN:oejs.HomeBaseWarning:main: This instance of Jetty is not running from a separate {jetty.base} directory, this is not recommended.  See documentation at http://www.eclipse.org/jetty/documentation/current/startup.html
2019-04-26 22:37:44.198:INFO:oejs.Server:main: jetty-9.3.27.v20190418, build timestamp: 2019-04-19T02:11:38+08:00, git hash: d3e249f86955d04bc646bb620905b7c1bc596a8d
2019-04-26 22:37:44.226:INFO:oejdp.ScanningAppProvider:main: Deployment monitor [file:///home/jetty/jetty-distribution-9.3.27.v20190418/webapps/] at interval 1
java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.eclipse.jetty.start.Main.invokeMain(Main.java:215)
	at org.eclipse.jetty.start.Main.start(Main.java:456)
	at org.eclipse.jetty.start.Main.main(Main.java:76)
Caused by: java.net.BindException: Address already in use
	at sun.nio.ch.Net.bind0(Native Method)
	at sun.nio.ch.Net.bind(Net.java:433)
	at sun.nio.ch.Net.bind(Net.java:425)
	at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:223)
	at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:74)
	at org.eclipse.jetty.server.ServerConnector.openAcceptChannel(ServerConnector.java:351)
	at org.eclipse.jetty.server.ServerConnector.open(ServerConnector.java:319)
	at org.eclipse.jetty.server.AbstractNetworkConnector.doStart(AbstractNetworkConnector.java:80)
	at org.eclipse.jetty.server.ServerConnector.doStart(ServerConnector.java:235)
	at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
	at org.eclipse.jetty.server.Server.doStart(Server.java:406)
	at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
	at org.eclipse.jetty.xml.XmlConfiguration$1.run(XmlConfiguration.java:1540)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.eclipse.jetty.xml.XmlConfiguration.main(XmlConfiguration.java:1462)
	... 7 more

Usage: java -jar start.jar [options] [properties] [configs]
       java -jar start.jar --help  # for more information

后台已读未读消息数量统计

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复盘踩坑

class="cursor-pointer"> 详细描述

JDBC与Mysql连接操作成功但是表格未更新

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JDBC

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public class StudentDAOImpl implements StudentDao {

Connection conn = null;
    PreparedStatement pstmt = null;
    ResultSet rs = null;

@Override
    public void addStudent(Student stu) {
        String sql = "INSERT INTO stu (id,create_at,update_at,name,qq,job,start_time,college,number,daily_url,wish,brother,referee,city,review) VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)";
//    String sql = "INSERT INTO stu (create_at,update_at,name,qq,job,start_time,college,number,daily_url,wish,brother,referee,city,review) VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?)";

try {
            conn = DBUtil.getConnecttion();
            System.out.println(conn+"************************");
            pstmt = conn.prepareStatement(sql);
            pstmt.setLong(1, stu.getId());
            pstmt.setLong(2, stu.getCreate_at());
            pstmt.setLong(3, stu.getUpdate_at());
            pstmt.setString(4, stu.getName());
            pstmt.setInt(5, stu.getQq());
            pstmt.setString(6, stu.getJob());
            pstmt.setLong(7, stu.getStart_time());
            pstmt.setString(8, stu.getCollege());
            pstmt.setInt(9, stu.getNumber());
            pstmt.setString(10, stu.getDaily_url());
            pstmt.setString(11, stu.getWish());
            pstmt.setString(12, stu.getBrother());
            pstmt.setString(13, stu.getReferee());
            pstmt.setString(14, stu.getCity());
            pstmt.setString(15, stu.getReview());
            System.out.println("添加学生成功");
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.closeAll(rs, pstmt, conn);
        }
    }

public class Test {
    public static void main(String[] args) {

//添加
        StudentDao sd=new StudentDAOImpl();
        sd.addStudent(new Student(11l,1l,2l,"曹非凡",123,"爪哇",3l,"牧专",123,"com",
                "money","王汇通","zhihu","zhengz","通过"));

class="cursor-pointer"> 错误截图

阿里云中迁移数据板块，无法加载腾讯云的bucket

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第三方API调用

class="cursor-pointer"> 详细描述

class="cursor-pointer"> 错误截图

Https是什么？怎么配置Https证书,Https究竟如何保证传输安全

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1

class="cursor-pointer"> 详细描述

Mybatis的if标签判空会把0判成空

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class="cursor-pointer"> 详细描述

class="cursor-pointer"> 错误截图

class="cursor-pointer"> 源码

    <!--根据id或状态或所属作品id查询留言-->
    <select id="selectMessage" resultMap="messageMap">
        SELECT * FROM message
        <where>
            <if test="messageId!=''and messageId!=null">
                message_id=#{messageId}
            </if>
            <if test="messageStatus ==0 or messageStatus == 1">
                AND message_status=#{messageStatus}
            </if>
            <if test="messageReplyWorkId !='' and messageReplyWorkId !=null">
                AND message_reply_work_id=#{messageReplyWorkId}
            </if>
            <if test="messageReplyId !='' and messageReplyId !=null">
                AND message_reply_id=#{messageReplyId}
            </if>
        </where>
        ORDER BY message_create_at DESC
    </select>

    public CodeMessageData selectMessage(Work workReceive, Message messageReceive, Integer pn, Integer num) {
        PageHelper.startPage(pn, num);
        Work work = new Work();
        work.setWorkName(workReceive.getWorkName());
        List<Work> workList = workMapper.selectWork(work);
        if(null==workList||workList.size()==0){
            return new CodeMessageData(0,"未找到该作品");
        }else{
            Message message = new Message();
            message.setMessageReplyWorkId(workList.get(0).getWorkId());
            message.setMessageReplyId(0L);
            message.setMessageStatus(messageReceive.getMessageStatus());
            List<Message> messageList = messageMapper.selectMessage(message);
            if (null == messageList || messageList.size() == 0) {
                return new CodeMessageData(0, "未找到该作品留言");
            } else {
                return new CodeMessageData(1, "查询成功", new PageInfo<Message>(messageList));
            }
        }
    }

    @RequestMapping(value = "/SelectMessage", method = RequestMethod.POST)
    public CodeMessageData selectMessage(Work workReceive, Message messageReceive, Integer pn, Integer num) {
        if(null!=messageReceive.getMessageStatus()&&(messageReceive.getMessageStatus()!=0&&messageReceive.getMessageStatus()!=1)){
            return new CodeMessageData(0,"留言状态错误");
        }else if(null==workReceive.getWorkName()||workReceive.getWorkName()==""){
            return new CodeMessageData(0,"留言所属作品名错误");
        }else if (null==pn||pn<=0||null==num||num<=0) {
            return new CodeMessageData(0, "页码错误");
        }else{
            return messageService.selectMessage(workReceive,messageReceive,pn,num);
        }

    }

@RequestPara和@PathVariable有什么区别？

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SSM

class="cursor-pointer"> 详细描述