HiSEN

发表于 | 分类于

之前我记得写过简单的测试类，但是忘了，现在重新写一个

顺便用博客记录下，mongodb系列应该会有几篇记录

本篇具体代码：SampleMongoTestNo1.java

1、环境介绍

mongodb安装教程：点击查看

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DataBase：MongoDB V 3.2
Driver　：3.4.1
maven：
    <dependency>
      <groupId>org.mongodb</groupId>
      <artifactId>mongo-java-driver</artifactId>
      <version>3.4.1</version>
    </dependency>

２、初始化连接

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private Mongo mg = null;
private DB db;
private DBCollection dbCollection;

@Before
public void initDB(){
  //建立连接
  mg = new MongoClient("127.0.0.1",27017);
  //获取要操作的数据库实例，没有会创建
  db = mg.getDB("hisen");
  //获取要操作的集合实例，没有会创建
  dbCollection = db.getCollection("emp");
}

3、关闭连接

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@After
  public void destoryDB(){
    if (mg == null) {
      mg.close();
      mg=null;
      db=null;
      dbCollection=null;
    }
  }

4、CRUD操作

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HiSEN

发表于 | 分类于

近期使用chrome出现打开一些网站老是弹出莫名其妙的网址

最终指向的都是Reimage Repair，网址zh.reimageplus.com
Reimage Repair
网上一查，貌似因为插件被污染的原因

我关闭chrome所有的插件，一个一个排查，最后找到了一个插件出问题

本来还想去举报，发现这个插件被下架了

问题排查

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右上角菜单按钮 ---更多工具 --- 扩展程序 --- 关闭所有插件
然后一个个打开，测试某些网页是否还会继续跳出那恶心的东西
然后就找到问题了。

HiSEN

发表于 | 分类于

在安装完ubuntu的时候

只有自己设置的非root的帐号和密码

但是又要用root密码怎么办呢？

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hisen@ubuntu-1:~$ sudo passwd
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

上面输入的密码就是你的root密码

检测一下

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hisen@ubuntu-1:~$ su
Password:
root@ubuntu-1:/home/hisen#

通过，至此结束

HiSEN

发表于 | 分类于

安装需求：

  1. 64位的系统 Linux/Unix/Mac
  2. 64bit JDK 1.8+;
  3. Maven 3.2.x;
  4. Git （一般自带）

如果还未安装jdk、maven建议查看教程:点击查看

Clone & Build

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git clone -b develop https://github.com/apache/incubator-rocketmq.git
cd incubator-rocketmq
mvn -Prelease-all -DskipTests clean install -U
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO] 
[INFO] Apache RocketMQ 4.2.0-incubating-SNAPSHOT .......... SUCCESS [01:07 min]
[INFO] rocketmq-remoting 4.2.0-incubating-SNAPSHOT ........ SUCCESS [ 15.749 s]
[INFO] rocketmq-common 4.2.0-incubating-SNAPSHOT .......... SUCCESS [ 10.243 s]
[INFO] rocketmq-client 4.2.0-incubating-SNAPSHOT .......... SUCCESS [ 11.638 s]
[INFO] rocketmq-store 4.2.0-incubating-SNAPSHOT ........... SUCCESS [ 13.108 s]
[INFO] rocketmq-srvutil 4.2.0-incubating-SNAPSHOT ......... SUCCESS [  2.051 s]
[INFO] rocketmq-filter 4.2.0-incubating-SNAPSHOT .......... SUCCESS [  3.917 s]
[INFO] rocketmq-broker 4.2.0-incubating-SNAPSHOT .......... SUCCESS [  8.726 s]
[INFO] rocketmq-tools 4.2.0-incubating-SNAPSHOT ........... SUCCESS [  6.002 s]
[INFO] rocketmq-namesrv 4.2.0-incubating-SNAPSHOT ......... SUCCESS [  2.726 s]
[INFO] rocketmq-logappender 4.2.0-incubating-SNAPSHOT ..... SUCCESS [  3.514 s]
[INFO] rocketmq-openmessaging 4.2.0-incubating-SNAPSHOT ... SUCCESS [  2.668 s]
[INFO] rocketmq-example 4.2.0-incubating-SNAPSHOT ......... SUCCESS [  2.390 s]
[INFO] rocketmq-filtersrv 4.2.0-incubating-SNAPSHOT ....... SUCCESS [  2.145 s]
[INFO] rocketmq-test 4.2.0-incubating-SNAPSHOT ............ SUCCESS [  5.428 s]
[INFO] rocketmq-distribution 4.2.0-incubating-SNAPSHOT .... SUCCESS [ 27.002 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 03:07 min
[INFO] Finished at: 2017-07-02T01:35:40+08:00
[INFO] Final Memory: 60M/247M
[INFO] ------------------------------------------------------------------------
cd distribution/target/apache-rocketmq

Start Name Server

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nohup sh bin/mqnamesrv &
tail -f ~/logs/rocketmqlogs/namesrv.log
The Name Server boot success...

Start Broker

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nohup sh bin/mqbroker -n localhost:9876 &
tail -f ~/logs/rocketmqlogs/broker.log 
The broker[%s, 172.30.30.233:10911] boot success...

Send & Receive Messages

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Before sending/receiving messages, we need to tell clients the location of name servers. RocketMQ provides multiple ways to achieve this. For simplicity, we use environment variable NAMESRV_ADDR
export NAMESRV_ADDR=localhost:9876
sh bin/tools.sh org.apache.rocketmq.example.quickstart.Producer
SendResult [sendStatus=SEND_OK, msgId= ...

sh bin/tools.sh org.apache.rocketmq.example.quickstart.Consumer 
ConsumeMessageThread_%d Receive New Messages: [MessageExt...

Shutdown Servers

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sh bin/mqshutdown broker
The mqbroker(36695) is running...
Send shutdown request to mqbroker(36695) OK

sh bin/mqshutdown namesrv
The mqnamesrv(36664) is running...
Send shutdown request to mqnamesrv(36664) OK

HiSEN

发表于 | 分类于

powerdesigner Oracle mysql comment 缺少右括号

今天人家给我个powerdesigner设计好的表

要我去间数据库，直接复制出来去oracle执行，结果报错。

在comment附近，如果把comment去掉则可以正确执行

最后找到罪魁祸首：powerdesigner没有设置对数据库

解决办法，在powerdesigner页面

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database-->change curren DBMS

上面是设置你需要的数据库

下面是为更改前的数据库

HiSEN

发表于 | 分类于

有时候需要行转列或者列转行

在Oracle 11g中，Oracle 又增加了2个查询：pivot（行转列） 和unpivot（列转行）

下面是在mysql中的操作：

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mysql> select * from test;
+------+------+--------+
| id   | age  | weigth |
+------+------+--------+
|    1 |    1 |      3 |
|    1 |    2 |      2 |
|    1 |    3 |      1 |
|    2 |    5 |      6 |
+------+------+--------+
4 rows in set (0.00 sec)

#根据ID分组
mysql> select group_concat(age) from test group by id;
+-------------------+
| group_concat(age) |
+-------------------+
| 1,2,3             |
| 5                 |
+-------------------+
2 rows in set (0.01 sec)

#不分组
mysql> select group_concat(age) from test;
+-------------------+
| group_concat(age) |
+-------------------+
| 1,2,3,5           |
+-------------------+
1 row in set (0.00 sec)

HiSEN

发表于 | 分类于

下面这个存储过程是查找数据库中某个字段值为：hisen 的表

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declare
l_cnt    varchar2(20);
v_sql  varchar2(4000);
v_tablename varchar(200);
  cursor cursor_jsdx is select 'select count(*) from ' || table_name || ' where NAME=''hisen''',table_name from user_tab_columns where column_name='NAME';
  --注：这里的字段名要大写
begin
     open cursor_jsdx;
     Loop
            fetch cursor_jsdx into v_sql,v_tablename;
            exit when cursor_jsdx%notfound;
            execute immediate v_sql       into l_cnt;           
         if l_cnt >0 then   
         ---如果该表有那内容的就打印那个表的名字。
            dbms_output.put_line(v_tablename);
         end if;
     end loop;
    Close cursor_jsdx;
end;

HiSEN

发表于 | 分类于

java.sql.SQLException: Connections could not be acquired from the underlying database

这个错误出现的原因有的说是因为jdbc配置文件写错了

正确的写法是：

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c3p0.driverClass=com.mysql.jdbc.Driver
c3p0.jdbcUrl=jdbc:mysql://localhost:3306/test
c3p0.user=root
c3p0.password=root

而不是

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driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/test
user=root
password=root

但是我遇到的不是如此

后来发现是因为maven出问题了，jar包没有加载进项目

这是在starkoverflow上看到的回答

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In my case it was problem that c3p0-0.9.2.1.jar file was not copied by maven into src/main/webapp/web-inf/libs

最后maven重新install之后就解决了

HiSEN

发表于 | 分类于

具体代码如下，这里获取出来的文件大小是准确的

FileInputStream方式获取出来的大小会有差异

NIO与IO的对比详见：NIOCopy.java

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/**
   * 利用NIO进行读写文件
   *
   * @param oldFileName 原文件的路径
   * @param newFileName 新文件的路径
   */
  public static void nioCopy(String oldFileName, String newFileName) {
    try {
      FileChannel fileChannelIn = new FileInputStream(new File(oldFileName)).getChannel();
      FileChannel fileChannelOut = new FileOutputStream(new File(newFileName)).getChannel();
      //获取文件大小
      long size = fileChannelIn.size();
      System.out.printf("文件大小为：%s byte \n",size);
      //缓冲
      ByteBuffer byteBuffer = ByteBuffer.allocate(1024);

      long start = System.currentTimeMillis();
      while (fileChannelIn.read(byteBuffer) != -1) {
        //准备写
        byteBuffer.flip();
        fileChannelOut.write(byteBuffer);
        //准备读
        byteBuffer.clear();
      }
      long end = System.currentTimeMillis();
      System.out.printf("NIO方式复制完成，耗时 %s 秒\n",(end-start)/1000);
      //关闭
      fileChannelIn.close();
      fileChannelOut.close();
    } catch (FileNotFoundException e) {
      e.printStackTrace();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }