平时在 Windows 上使用 gVim 来编辑文本。将一些常用的技巧记录下来。

VIM tips

常用指令/快捷键

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# 光标移动
gg, G, H, M, L, 8j, fc
Ctrl+F, Ctrl+B, Ctrl+D, Ctrl+U
Ctrl+O
# 
# tab 标签栏的移动: 跳到下一个tab, 上一个tab, 第三个tab:
gt, gT, 3gt
# 查看打开的所有 buffer:
:ls
# 跳到前一个，后一个，第3个buffer:
:bp, :bn, ：b3

删除文件中的 ^M 字符

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:%s/^M$//g

注：^M的输入：兼容模式下，要用 Ctrl+Q Ctrl+M / 标准模式下，则为 Ctrl+V Ctrl+M

删除偶数行

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:g/^/+1 d

删除纯数字行

当从网页上拷页代码时，若其代码插件不完善，将行号也拷贝下来了，一个行号一行。此时，可进入命令模式，用 Shift+v 及 <num>j, ctrl+d 选中该代码段，再按:，则最下方的状态栏出现 :'<,'>，输入指令：g/^\d*$/d，即执行：

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:'<,'>g/^\d*$/d

则会将只有行号的行删除。

Issue

The webapp hang at:

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INFO: Initializing Spring root WebApplicationContext

when startup.

Solution

Enable logging for Spring in logback.xml to check the startup process:

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<logger name="org.springframework" level="DEBUG" />

Byte array to hex string

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public static String toHexString(byte[] array) {
    return javax.xml.bind.DatatypeConverter.printHexBinary(array);
}

Code in comments

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/**
 * <PRE>
 * insert code as you would anywhere else
 * </PRE>
 */

An Example from a java.awt.Event method javadoc:

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/**
 * <PRE>
 *    int onmask = SHIFT_DOWN_MASK | BUTTON1_DOWN_MASK;
 *    int offmask = CTRL_DOWN_MASK;
 *    if ((event.getModifiersEx() & (onmask | offmask)) == onmask) {
 *        ...
 *    }
 * </PRE>
 */

Get field descriptions (names)

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public static <T, K> Map<K, String> getFieldDescriptions(Class<T> clazz) {
	Map<K, String> map = new HashMap<K,String>();
	for (Field f : clazz.getDeclaredFields()) {
		int mod = f.getModifiers();
		if (Modifier.isPublic(mod) && Modifier.isFinal(mod) && Modifier.isStatic(mod)) {
			try {
				@SuppressWarnings("unchecked")
				K fld = (K) f.get(null);
				
				Integer st = null;
				if (fld instanceof Integer) {
					st = (Integer) fld;
				} else if (fld instanceof Short) {
					st = (int) (short) (Short) fld;
				}
				map.put(fld, String.format("0x%04X, %s", st&0xFFFFFFFF, f.getName()));
			} catch (Exception ex) {
				/* ignore */
			}
		}
	}
	
	return map;
}

Some tips for Tomcat7.

Move the constant lib as external libs:

• Step 1: Copy the lib to somewhere else, e.g. ${catalina.home}/anyfish-lib
• Step 2: Eclipse: Properties for app > Deployment Assembly > Remove ‘Maven Dependencies’
• Step 3: Add following config in /conf/context.xml:

  1	<Loader className="org.apache.catalina.loader.VirtualWebappLoader" virtualClasspath="${catalina.home}/anyfish-lib/*.jar" />

So the final packaged .war file size is reduced dramatically!

To achive Step 2 in maven, edit the pom.xml file:

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<properties>
	<maven.build.timestamp.format>yyyyMMddHHmm</maven.build.timestamp.format>
</properties>
<build>
	<plugins>
		<plugin>
			<groupId>org.apache.maven.plugins</groupId>
			<artifactId>maven-war-plugin</artifactId>
			<version>2.4</version>
			<configuration>
				<warName>${project.artifactId}##${maven.build.timestamp}</warName>
				<packagingExcludes>%regex[WEB-INF/lib/(?!mylib-1.0.0-SNAPSHOT).*.jar]</packagingExcludes>
			</configuration>
		</plugin>
	</plugins>
</build>

Note the <packagingExcludes>%regex[WEB-INF/lib/(?!mylib-1.0.0-SNAPSHOT).*.jar]</packagingExcludes> config above (Don’t package the common spring, logging libaries etc into .war file; keep only mylib.jar).

Deploy new version w/o shutting down tomcat

To deploy a new version of webapp without shutting down tomcat, use parallel deployment in tomcat7, refer to tomcat parallel deploy.

Note the <warName>${project.artifactId}##${maven.build.timestamp}</warName> config above.

使用国内的镜像地址

mavn 中央库默认的下载地址在国外，下载速度不稳定。开源中国做了国内镜像，参考其帮助文档配置其为中央库：

备份 Maven 的安装目录下的 conf/settings.xml 文件，再编辑它：

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<mirrors>
	<!-- http://maven.oschina.net/static/help.html -->
	<mirror>
		<id>nexus-osc</id>
		<mirrorOf>*</mirrorOf>
		<name>Nexus OSC</name>
		<url>http://maven.oschina.net/content/groups/public/</url>
	</mirror>
</mirrors>
<profiles>
	<!-- http://maven.oschina.net/static/help.html -->
	<profile>
		<id>jdk-1.4</id>
		<activation><jdk>1.4</jdk></activation>
		<repositories>
			<repository>
				<id>nexus</id>
				<name> local private nexus</name>
				<url>http://maven.oschina.net/content/groups/public</url>
				<releases><enabled>true</enabled></releases>
				<snapshots><enabled>false</enabled></snapshots>
			</repository>
		</repositories>
		<pluginRepositories>
			<pluginRepository>
				<id>nexus</id>
				<name>local private enxus</name>
				<url>http://maven.oschina.net/content/groups/public</url>
				<releases><enabled>true</enabled></releases>
				<snapshots><enabled>false</enabled></snapshots>
			</pluginRepository>
		</pluginRepositories>
	</profile>
</profiles>

自定义生成 war 包的内容和文件名

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<properties>
	<maven.build.timestamp.format>yyyyMMddHHmm</maven.build.timestamp.format>
</properties>
<build>
	<plugins>
		<plugin>
			<groupId>org.apache.maven.plugins</groupId>
			<artifactId>maven-war-plugin</artifactId>
			<version>2.4</version>
			<configuration>
				<warName>${project.artifactId}##${maven.build.timestamp}</warName>
				<packagingExcludes>%regex[WEB-INF/lib/(?!mylib-1.0.0-SNAPSHOT).*.jar]</packagingExcludes>
			</configuration>
		</plugin>
	</plugins>
</build>

以上配置，

• 在生成的 war 包名字的后面加上打包时间；
• 不 将公共的 spring, json 的相关 jar 包打到最终 war 包中，只保留自己的、经常会变化的 mylib-1.0.0-SNAPSHOT，参见Tomcat Tips。

背景知识： tomcat的并行部署

部署新版本时，一般要先停掉旧的应用，复制新应用后，再启动tomcat，这就造成中间有一段时间 tomcat 是无法对外服务的。

从Tomcat 7.0.23+开始，可以在不关闭 Tomcat 的情况下同时部署相同context path的多个不同版本的web应用。war包的命名格式形如context.war, context##2.war,context##3.war。

当用户访问 http://[url]/context 时，规则如下:

• 如果当前请求没有session信息，则使用最新的war应用版本
• 如果当前请求有session，使用session对应的war应用版本
• 如果当前请求有session信息，却找不到相应的war应用版本，则使用最新的war应用版本（context##3.war）

实现并行部署

1. pom.xml 中配置生成的 war 包加时间戳：

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<properties>
	<maven.build.timestamp.format>yyyyMMddHHmm</maven.build.timestamp.format>
</properties>
<build>
	<plugins>
		<plugin>
			<groupId>org.apache.maven.plugins</groupId>
			<artifactId>maven-war-plugin</artifactId>
			<version>2.4</version>
			<configuration>
				<warName>${project.artifactId}##${maven.build.timestamp}</warName>
				<packagingExcludes>%regex[WEB-INF/lib/(?!mylib-1.0.0-SNAPSHOT).*.jar]</packagingExcludes>
			</configuration>
		</plugin>
	</plugins>
</build>

在项目根目录下执行命令

mvn package

生成 war 包，如 portal##20140922.war。

2. 部署

将 war 包上传到/anyfish_web/war/warHub 下后，执行部署脚本 parallelDeploy.sh （脚本内容见下）

部署脚本

并行部署脚本 parallelDeploy.sh 的功能：搜寻指定目录下最新的 war 包，然后依 Tomcat 格式，在 $TOMCAT_HOME/conf/Catalina/localhost 创建配置文件（如 portal##20140922.xml），以使 Tomcat 感知并部署此 web 工程。

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# conf
ctx=portal
warFolder=/anyfish_web/war/warHub
deployFolder=/anyfish_web/war
confFolder=/Tomcat/conf/Catalina/localhost
# ---
latestWarFile=$(basename `ls -tr $warFolder/*.war | tail -n 1`)
echo --- latestWarFile: $latestWarFile
cp $warFolder/$latestWarFile $deployFolder/
confFile=$(echo $latestWarFile | sed 's/.*\#\#\(.*\)\.war/\1/')
ctxXml=$confFolder/$ctx##$confFile.xml
# generate context conf file for tomcat to deploy
echo --- ctxXml: $ctxXml
ctxCont='<Context displayName="'$ctx'" docBase="/anyfish_web/war/'$latestWarFile'" reloadable="true" />'
echo $ctxCont > $ctxXml

Normal user: vi ~/.bashrc

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export PS1="\n\e[0;33m[\t \u@\h \W]\$ \e[m"

Root user (set as red #):

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export PS1="\n\e[0;31m[\t  \u@\h \W]\$ \e[m"

References:

• Change The Color of My Shell Prompt Under Linux or UNIX
• Bash Prompt Escape Sequences

You need to implement the HttpSessionListener interface. It receives notification events when session is created, or destroyed. In particular, its method sessionDestroyed(HttpSessionEvent se) gets called when the session is destroyed, which happens after timeout period has finished / session was invalidated. You can get the information stored in the session via HttpSessionEvent#getSession() call, and later do any arrangements that are necessary with the session. Also, be sure to register your session listener in web.xml:

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<listener>
    <listener-class>FQN of your sessin listener implementation</listener-class>
</listener>

If you ultimately want to distinguish between invalidation and session timeout you could use the following line in your listener:

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long now = new java.util.Date().getTime();
boolean timeout = (now - session.getLastAccessedTime()) >= ((long)session.getMaxInactiveInterval() * 1000L);

Reference:

• stackoverflow