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Fri, 08 Dec 2017 06:13:00 GMT

在Spring cloud config出来之前, 自己实现了基于ZK的配�|�中�? 杜绝了本地properties配置文�g, 原理很简�? 只是重蝲了PropertyPlaceholderConfigurer的mergeProperties():

/**
 * 重蝲合�ƈ属性实�?br /> * 先加载file properties�Q?然后�q�入ZK配置中心��d��的properties
 *
 * @return 合�ƈ后的属性集�?br /> * @throws IOException 异常
 */
@Override
protected Properties mergeProperties() throws IOException {
    Properties result = new Properties();
    // 加蝲父类的配�|?br />    Properties mergeProperties = super.mergeProperties();
    result.putAll(mergeProperties);
    // 加蝲从zk中读取到的配�|?br />    Map, String> configs = loadZkConfigs();
    result.putAll(configs);
    return result;
}

�q�个实现在spring��目里用��h��q�是挺顺手的, 但是�q�期部分spring-boot��目里发现这�U�placeholder的实现跟spring boot的@ConfigurationProperties(prefix = "xxx") 不能很好的配合工�?
也就是属性没有被resolve处理, 用@Value的方式确可以��d��, 但是@Value配置��h��如果属性多的话�q�是挺繁琐的, �q�是們֐�用@ConfigurationProperties的prefix, 于是看了下spring boot的文��发�?code>PropertySource order:

   * Devtools global settings properties on your home directory (~/.spring-boot-devtools.properties when devtools is active).
   * @TestPropertySource annotations on your tests.
   * @SpringBootTest#properties annotation attribute on your tests.
   * Command line arguments.
   * Properties from SPRING_APPLICATION_JSON (inline JSON embedded in an environment variable or system property)
   * ServletConfig init parameters.
   * ServletContext init parameters.
   * JNDI attributes from java:comp/env.
   * Java System properties (System.getProperties()).
   * OS environment variables.
   * A RandomValuePropertySource that only has properties in random.*.
   * Profile-specific application properties outside of your packaged jar (application-{profile}.properties and YAML variants)
   * Profile-specific application properties packaged inside your jar (application-{profile}.properties and YAML variants)
   * Application properties outside of your packaged jar (application.properties and YAML variants).
   * Application properties packaged inside your jar (application.properties and YAML variants).
   * @PropertySource annotations on your @Configuration classes.
   * Default properties (specified using SpringApplication.setDefaultProperties).

不难发现其会��查Java system propeties里的属�? 也就是说, 只要把mergerProperties��d��的属性写入Java system props里即�? 看了下源�? 扑ֈ�个切入点

/**
 * 重蝲处理属性实�?br /> * �Ҏ��选项, 军_��是否���合�q�后的props写入�pȝ��属�? Spring boot需�?br /> *
 * @param beanFactoryToProcess
 * @param props                合�ƈ后的属�?br /> * @throws BeansException
 */
@Override
protected void processProperties(ConfigurableListableBeanFactory beanFactoryToProcess, Properties props) throws BeansException {
    // 原有逻辑
     super.processProperties(beanFactoryToProcess, props);
    // 写入到系�l�属�?br />    if (writePropsToSystem) {
       // write all properties to system for spring boot
        Enumeration propertyNames = props.propertyNames();
        while (propertyNames.hasMoreElements()) {
             String propertyName = (String) propertyNames.nextElement();
             String propertyValue = props.getProperty(propertyName);
             System.setProperty(propertyName, propertyValue);
        }
    }
}

为避免媄响过�? 讄��了个开�? 是否写入�pȝ��属�? 如果是spring boot的项�? ��开�? �q�样对线上非spring boot��目做到影响最��? 然后spring boot的@ConfigurationProperties完美��d��属�?

具体代码�? org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor

@Override
public Object postProcessBeforeInitialization(Object bean, String beanName)
      throws BeansException {
   ConfigurationProperties annotation = AnnotationUtils
         .findAnnotation(bean.getClass(), ConfigurationProperties.class);
   if (annotation != null) {
      postProcessBeforeInitialization(bean, beanName, annotation);
 }
   annotation = this.beans.findFactoryAnnotation(beanName,
 ConfigurationProperties.class);
   if (annotation != null) {
      postProcessBeforeInitialization(bean, beanName, annotation);
 }
   return bean;
}

Milo的�v�?/a> 2017-12-08 14:13 发表评论

Sat, 15 Apr 2017 02:32:00 GMT

Spring默认不允许对�cȝ��变量, 也就是静态变量进行注入操�? 但是在某些场景比如单元测试的@AfterClass要访问注入对�? 而Junit的这个方法必��L��静态的, 也就产生了悖�?

解决思�\有两�?

思�\1: 惛_��法对静态变量注�? 也就是绕�q�Spring只能�q�行非静态变量才能注入依赖的壁垒
思�\2: 惛_��法@AfterClass攚w��ؓ非静�?/span>
- 实现Junit RunListener, 覆盖testRunFinished�Ҏ��, �q�里��d��现类似@AfterClass的功�? �q�个�Ҏ��是非静态的
- 不要用Junit, 改用TestNG, TestNG里的AfterClass是非静态的
- 用Spring的TestExecutionListeners, 实现个Listener, 里面也有个类似非静态的AfterClass的实�? 覆盖实现��p��

思�\2的几个方法都可以实现, 但是单元��试Runner需要用

@RunWith(Theories.class)

而且改用TestNG工程��大, 只能攑ּ�掉这个思�\

�l�箋走思�\1, 只能�ȝ��q�Spring的依赖注入的static壁垒�? 具体代码如下:

 @Autowired
 private Destination dfsOperationQueue;
 private static Destination dfsOperationQueueStatic; // static version
 @Autowired
 private MessageQueueAPI messageQueueAPI;
 private static MessageQueueAPI messageQueueAPIStatic; // static version


 @PostConstruct
 public void init() {
        dfsOperationQueueStatic = this.dfsOperationQueue;
        messageQueueAPIStatic = this.messageQueueAPI;
 }

 @AfterClass
 public static void afterClass() {
        MessageVO messageVO = messageQueueAPIStatic.removeDestination(dfsOperationQueueStatic);
        System.out.println(messageVO);
 }

其实��是用了@PostConstruct 来个��h��换柱而已, 多声明个静态成员指向非静态对�? 两者其实是一个对�?/span>

Milo的�v�?/a> 2017-04-15 10:32 发表评论

通过rest api��理activemq

Sat, 22 Oct 2016 09:31:00 GMT

知道activemq现在已经支持了rest api, 但是官方对这部分的介�l�一�W�带�q?(http://activemq.apache.org/rest.html),

通过google居然也没搜到一些有用的, 比如像删除一个destination, 都是问的�?然后没下�? 于是�׃��一些心思研�I�了一�?

首先通过rest api获取当前版本所有已支持的协�?/p>

http://172.30.43.206:8161/api/jolokia/list

然后�Ҏ��json输出关于removeTopic, removeQueue的mbean实现通过rest api删除destination的方�? 注意到用GET��h��而不是POST,不然会报�?(官网的例子里用的wget�l�的灉|��, 开始用了POST老报�?

import org.apache.activemq.command.ActiveMQQueue;
import org.apache.activemq.command.ActiveMQTopic;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.client.DefaultHttpClient;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.http.client.ClientHttpRequestFactory;
import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;

import javax.jms.Destination;
import javax.jms.JMSException;
import java.util.Arrays;

public class MessageQueueAdmin {
    private static final RestTemplate restTemplate = getRestTemplate("admin", "admin");

    private static String brokerHost = "172.30.43.206";
    private static String adminConsolePort = "8161";
    private static String protocol = "http";

    public static void removeDestination(Destination destination) throws JMSException {
        String destName, destType;
        if (destination instanceof ActiveMQQueue) {
            destName = ((ActiveMQQueue) destination).getQueueName();
            destType = "Queue";
        } else {
            destName = ((ActiveMQTopic) destination).getTopicName();
            destType = "Topic";
        }

        // build urls
        String url = String.format("%s://%s:%s/api/jolokia/exec/org.apache.activemq:" +
                "brokerName=localhost,type=Broker/remove%s/%s", protocol, brokerHost, adminConsolePort, destType, destName);
        System.out.println(url);
        // do operation
        HttpHeaders headers = new HttpHeaders();
        headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
        HttpEntity<String> entity = new HttpEntity<String>("parameters", headers);
        ResponseEntity response = restTemplate.exchange(url, HttpMethod.GET, entity, String.class);
        System.out.println(response.getBody());
    }

    public static void main(String[] args) throws JMSException {
        ActiveMQTopic topic = new ActiveMQTopic("test-activemq-topic");
        removeDestination(topic);
    }

    private static RestTemplate getRestTemplate(String user, String password) {
        DefaultHttpClient httpClient = new DefaultHttpClient();
        BasicCredentialsProvider credentialsProvider = new BasicCredentialsProvider();
        credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials(user, password));
        httpClient.setCredentialsProvider(credentialsProvider);
        ClientHttpRequestFactory rf = new HttpComponentsClientHttpRequestFactory(httpClient);

        return new RestTemplate(rf);
    }
}

其他的请�?应该都是�c�M��jolokia的exec get request的格�?

https://jolokia.org/reference/html/protocol.html#exec

/exec/////.

Milo的�v�?/a> 2016-10-22 17:31 发表评论

Wed, 12 Oct 2016 08:32:00 GMT

用Spring JMS 的JmsTemplate从消息队列消�Ҏ��息时发现�Q��用了CLIENT_ACKNOWLEDGE模式�Q�消息返回后��L��自动被ack�Q�也��是被broker "Dequeued"

    protected Message doReceive(Session session, MessageConsumer consumer) throws JMSException {
        try {
            // Use transaction timeout (if available).
            long timeout = getReceiveTimeout();
            JmsResourceHolder resourceHolder =
                    (JmsResourceHolder) TransactionSynchronizationManager.getResource(getConnectionFactory());
            if (resourceHolder != null && resourceHolder.hasTimeout()) {
                timeout = Math.min(timeout, resourceHolder.getTimeToLiveInMillis());
            }
            Message message = doReceive(consumer, timeout);
            if (session.getTransacted()) {
                // Commit necessary - but avoid commit call within a JTA transaction.
                if (isSessionLocallyTransacted(session)) {
                    // Transacted session created by this template -> commit.
                    JmsUtils.commitIfNecessary(session);
                }
            }
            else if (isClientAcknowledge(session)) {
                // Manually acknowledge message, if any.
                if (message != null) {
                    message.acknowledge();
                }
            }
            return message;
        }
        finally {
            JmsUtils.closeMessageConsumer(consumer);
        }
    }

但是使用异步listener ��׃��会出现这个情况，搜了下google�Q�发现果然存在这个问�?br />

     https://jira.spring.io/browse/SPR-12995
     https://jira.spring.io/browse/SPR-13255
     http://louisling.iteye.com/blog/241073

同步方式拉取消息�Q�暂时没扑ֈ�好的��装�Q�只能暂时用�q�。或者尽量用listener, �q�个问题暂时标记下，或者谁有更好的解决�Ҏ��可以comment�?img src ="http://www.tkk7.com/miaoyachun/aggbug/431885.html" width = "1" height = "1" />

Milo的�v�?/a> 2016-10-12 16:32 发表评论

Thu, 26 May 2016 06:14:00 GMT

http://stackoverflow.com/questions/3294423/spring-classpath-prefix-difference

SIMPLE DEFINITION

The classpath*:conf/appContext.xml simply means that all appContext.xml files under conf folders in all your jars on the classpath will be picked up and joined into one big application context.

In contrast, classpath:conf/appContext.xml will load only one such file the first one found on your classpath.

<bean id="propertyConfigurer"
 class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
   <property name="locations">
      <list>
         <value>classpath:*.propertiesvalue>
         <value>classpath*:*.propertiesvalue>
      list>
   property>
bean>

Milo的�v�?/a> 2016-05-26 14:14 发表评论

When launched from .exe IDEA looks for Java in a following order

Mon, 16 May 2016 00:49:00 GMT

IDEA_JDK (or IDEA_JDK_64) environment variable
jre/ (or jre64/) directory in IDEA home
registry
JDK_HOME environment variable
JAVA_HOME environment variable

Milo的�v�?/a> 2016-05-16 08:49 发表评论

Thu, 21 Apr 2016 09:06:00 GMT

java里如何修改console的历史输��Z��息呢�Q�如果是当前行的修改可以��单想�?\r"的方案，但是如果要修改上一行呢? google了下原来�q�是有方法的�Q�需要用到ansi的control sequences
ANSI code

用java写了个简单的例子�Q�例子就是把曄��的output修改为其他字�W�串�q�恢复之后的打印�Q�代码里加了sleep�Q�主要方便理解各�U�控制序列的含义

        //print some test messages
        System.out.println("1");
        Thread.sleep(1000);
        System.out.println("22");
        Thread.sleep(1000);
        System.out.println("333");
        Thread.sleep(1000);
        System.out.println("4444");
        Thread.sleep(1000);

        /**
         * modify "333" to "-"
         */
        // Move up two lines
        int count = 2;
        System.out.print(String.format("\033[%dA", count));
        Thread.sleep(1000);
        // Erase current line content
        System.out.print("\033[2K");
        Thread.sleep(1000);
        // update with new content
        System.out.print("-");
        Thread.sleep(1000);
        // Move down two lines
        System.out.print(String.format("\033[%dB", count));
        Thread.sleep(1000);
        // Move cursor to left beginning
        System.out.print(String.format("\033[D", count));
        // continue print others
        Thread.sleep(1000);
        System.out.println("55555");
        Thread.sleep(1000);

Milo的�v�?/a> 2016-04-21 17:06 发表评论

zookeeper学习

Thu, 31 Mar 2016 06:06:00 GMT

1. zookeeper basic/fast paxsos 的�Ş象表�q?https://www.douban.com/note/208430424/
2. 详细介绍 http://blog.csdn.net/xhh198781/article/details/10949697

Milo的�v�?/a> 2016-03-31 14:06 发表评论

Spring boot 开启reponse压羃以及部分参数讄��

Tue, 29 Mar 2016 03:50:00 GMT

server.compression.enabled=true 
server.compression.mime-types=application/json,application/xml,text/html,text/xml,text/plain
server.compression.min-response-size=4096

�W�一个参数打开压羃开养I��W�二个参数添加json reponse�Q�尤其是为rest api�Q?�W�三个参数是�Ҏ��reponse的大��设�|�启用压�~�的最��?默认�?K�Q�自己根据实际情况调�?

参�?div>http://docs.spring.io/spring-boot/docs/current-SNAPSHOT/reference/htmlsingle/#how-to-enable-http-response-compression

Milo的�v�?/a> 2016-03-29 11:50 发表评论

Wed, 16 Mar 2016 07:40:00 GMT

1. 默认�?个classloader: BootstrapClassloader (Native实现)�Q?ExtClassloader, AppClassloader (Java实现)
2. 3个加载器�q�不是真正的父子�l�承关系�Q�而是逻辑上的�Q�JVM启动先创建ExtClassloader instance�Q�然后构造AppClassloader的时候传入ExtClassloader实例作�ؓparent

        Launcher.ExtClassLoader extcl;
        try {
            extcl = Launcher.ExtClassLoader.getExtClassLoader();
        } catch (IOException var10) {
            throw new InternalError("Could not create extension class loader", var10);
        }

        try {
            this.loader = Launcher.AppClassLoader.getAppClassLoader(extcl);
        } catch (IOException var9) {
            throw new InternalError("Could not create application class loader", var9);
        }

关于双亲委派原理�Q?在加载类的时候，会看看parent有没有设定，如果讑֮��?��p��用parent.loadClass�Ҏ��Q�如果没讑֮�(==null)也就是parent应该是BootstrapClassloader, 会调用native的findBootstrapClass来加载类�Q�代码：

                try {
                    if(this.parent != null) {
                        c = this.parent.loadClass(name, false);
                    } else {
                        c = this.findBootstrapClassOrNull(name);
                    }
                } catch (ClassNotFoundException var10) {
                    ;
                }

目的是按照一定优先��别装载系�l�的lib�Q�系�l�ext目录的lib�Q�以及classpath的lib�Q�防止系�l�的默认行�ؓ或者类的实现被修改�?br />
3. java �cȝ��动态加�?br />

Java内置的ClassLoader��M��在加载一个Class之前��查这个Class是否已经被加载过�Q�已�l�被加蝲�q�的Class不会加蝲�W�二�ơ。因此要想重新加载Class�Q�我们需要实现自��q��ClassLoader�?
另外一个问题是�Q�每个被加蝲的Class都需要被链接(link)�Q�这是通过执行ClassLoader.resolve()来实现的�Q�这个方法是 final的，因此无法重写。Resove()�Ҏ��不允�怸�个ClassLoader实例link一个Class两次�Q�因此，当你需要重新加载一�? Class的时候，你需要重新New一个你自己的ClassLoader实例�?

Milo的�v�?/a> 2016-03-16 15:40 发表评论

��目中用到的一些maven插�g�ȝ��

Tue, 26 Jan 2016 03:41:00 GMT

maven-shade-plugin 用来打可执行jar包，可以把所有依赖的三方库都包括�q�来
exec-maven-plugin 可以执行外部命��o�Q?nbsp;在项目中对python代码�q�行�~�译�Q?nbsp;配合maven-assembly-plugin来生成package
maven-assembly-plugin 用来构徏��目发行包，要配合xml配置文�g来组�l�包的结构，基本思�\是从build环境copy到outputDirectory
license-maven-plugin 用来生成��目用到�?方库的版权汇�?nbsp;或者其他的一些用�?br />maven-dependency-plugin 用来生成��目库之间的依赖关系
appassembler-maven-plugin 可以为项目生成优雅的启动脚本支持linux/win
rpm-maven-plugin 用来为项目构建rpm安装�?br />maven-compiler-plugin 指定��目的jdk的编译兼容版本以及encoding�c�d��

Milo的�v�?/a> 2016-01-26 11:41 发表评论

Wed, 21 Oct 2015 09:12:00 GMT

��目用mvn exec:exec指��o来启动server, 工作中需要调式server初始化的�q�程, 很容易想到mvnDebug, 但是发现讄��的断炚w��没有hit, 反复调式多次都是如此,折腾�?个多��时, �H�然看到stackoverflow 上有��exec:exec是独立进�E�模�? mvnDebug的一些debug选项都被append��C��父进�E�了. idea讄��断点��q��q�卵�?

知道了问题所在解军_��Ҏ��? 只要修改pom.xml, 然后直接mvn exec:exec��p��正常调式�?br />

                        org.codehaus.mojo
                        exec-maven-plugin
                        ${mvnexec.version}



                                    exec




                            true
                            java
                            ${basedir}/config/sim
                            runtime

                                -agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=4000
                                -classpath

                                com.ymiao.Main
                                server
                                ${basedir}/config/sim/sim.yml

�ȝ��是exec:exec是要独立一个新�q�程来执行程序的, exec:java��q��? 其实用mvnDebug + exec:java也是理论可行�?img src ="http://www.tkk7.com/miaoyachun/aggbug/427858.html" width = "1" height = "1" />

Milo的�v�?/a> 2015-10-21 17:12 发表评论

关于jconsole昄��自定义的MBean

Tue, 08 Sep 2015 02:53:00 GMT

��目中要用到MBean,于是快速体验下�Q�体验过�E�中发现2个问�?

自定义的Mbean的普通method能在jconsole的Mbeans里显�C�出来，但是涉及到geters/seters��无法显�C�Z��
如果MBean注册��C��面�Ş式创建的MBeanServer在Jconsole上无法显�C�的
MBeanServer server = MBeanServerFactory.createMBeanServer();
但是如果注册��C��面的形式创徏的Server在Jconsole上是可以昄��MBean�?br />
MBeanServer server = ManagementFactory.getPlatformMBeanServer();

stackoverflow上也有�h发现�q�个问题

http://stackoverflow.com/questions/7424009/mbeans-registered-to-mbean-server-not-showing-up-in-jconsole

Milo的�v�?/a> 2015-09-08 10:53 发表评论

java 帔R��池从jdk7开始从�Ҏ��U�d��堆内

Wed, 06 May 2015 09:35:00 GMT

从jdk7最开始的release version (http://www.oracle.com/technetwork/java/javase/jdk7-relnotes-418459.html)的notes里看�?br />
Area: HotSpot
Synopsis: In JDK 7, interned strings are no longer allocated in the permanent generation of the Java heap, but are instead allocated in the main part of the Java heap (known as the young and old generations), along with the other objects created by the application. This change will result in more data residing in the main Java heap, and less data in the permanent generation, and thus may require heap sizes to be adjusted. Most applications will see only relatively small differences in heap usage due to this change, but larger applications that load many classes or make heavy use of the String.intern() method will see more significant differences.
RFE: 6962931

Milo的�v�?/a> 2015-05-06 17:35 发表评论

Sat, 28 Feb 2015 08:51:00 GMT

今天有同事问��Z��么ubuntu上启动jenkins��p�|�Q�我记得之前玩的时候�ƈ没有出现�q�种情况�Q�于是跟�t�了下，最�l�错误信息是:

daemon: fatal: refusing to execute unsafe program: /usr/bin/java (/opt is group and world writable)

�Ҏ��原因是机器装了多个版本的jdk, jdk所在的/opt父目录的权限攄��比较大，按照daemon要求的限制到755

chmod -R 755 /opt

问题��p��决了�?br />
其实�q�个场景�q�是蛮常见的�Q�遇到的人应该挺多的

Milo的�v�?/a> 2015-02-28 16:51 发表评论

valgrind memory check on java program

Fri, 06 Dec 2013 02:26:00 GMT

Java�E�序的memory leak分析也可以用valgrind, ��其是JNI�E�序��其有用:

valgrind --error-limit=no --trace-children=yes --smc-check=all --leak-check=full JAVA_CMD

�Ҏ��写了个有leak的jni函数�Q�用valgrind成功��查出来了

==31915== 100 bytes in 1 blocks are definitely lost in loss record 447 of 653
==31915== at 0x402CE68: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==31915== by 0x60424F9: Java_MyJNI_hello (MyJNI.c:16)

在老版本valgrind(3.5.0) enable�?-trace-children选项后可能出现错�?

 Error occurred during initialization of VM    
 Unknown x64 processor: SSE2 not supported

升��到最新版可以解决�q�个问题�Q�升�U�方法：下蝲src�?解压后执�?./configure; make; make install

Milo的�v�?/a> 2013-12-06 10:26 发表评论

maven本地三方依赖包插件addjars-maven-plugin

Wed, 30 Oct 2013 06:03:00 GMT

maven��目中有很多本地三方依赖�Q�但是一个一个加入dependency + system scope又很�ȝ��Q�又貌似没有搜烦到通配�W�的成功案例�Q�但是从stackoverflow上看��C��个插件addjars-maven-plugin, 可以很好解决�q�类需�?

    <build>
        <plugins>
            <plugin>
                <groupId>com.googlecode.addjars-maven-plugingroupId>
                <artifactId>addjars-maven-pluginartifactId>
                <version>1.0.2version>
                <executions>
                    <execution>
                        <goals>
                            <goal>add-jarsgoal>
                        goals>
                        <configuration>
                            <resources>
                                <resource>
                                    <directory>${basedir}/../libdirectory>
                                resource>
                            resources>
                        configuration>
                    execution>
                executions>
            plugin>
            <plugin>
                <groupId>org.apache.maven.pluginsgroupId>
                <artifactId>maven-assembly-pluginartifactId>
                <version>${maven.assembly.version}version>
                <configuration>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependenciesdescriptorRef>
                    descriptorRefs>
                    <appendAssemblyId>falseappendAssemblyId>
                configuration>
                <executions>
                    <execution>
                        <phase>packagephase>
                        <goals>
                            <goal>singlegoal>
                        goals>
                    execution>
                executions>
            plugin>
        plugins>
    build>

把项目中依赖的三方jars全放到lib目录里，��全部会打包到release jar里了

Milo的�v�?/a> 2013-10-30 14:03 发表评论

反编译java class�q�优雅的调试

Fri, 22 Feb 2013 07:01:00 GMT

用jd-eclipse 插�g来反�~�译java class文�g的输��是挺nice的，虽然阅读方便�?但是对debug��造成一定的困扰�Q�主要问题是line number的不match.
Google了下遇到�c�M��问题的真不少。最�l�找��C��解决�Ҏ��Q?br />

http://sourceforge.net/projects/realignmentjd/files/
-----------------

1. Download JD-Eclipse and JD-GUI - http://java.decompiler.free.fr/ and install.
2. Put a file realignment.jd.ide.eclipse_1.0.2.jar in eclipse/plugins directory.
    To use Realignment feature it is necessary to open the menu Preferences/General/Editors/File Associations and to select "*.class" file type and to choose "Realignment for JD Class File Editor" for Associated editors.
    Another possibility is the batch realignment after processing JD-GUI. To work properly you must to switch on the property "Display line numbers" in Help/Preferences of JD-GUI.
    To use this feature it is necessary to open the menu Preferences/Java/Decompiler/Batch Realignment and click button "Open dialog". Existing limitation: the realignment is performed only for the methods.
To work properly it is necessary that the property "Display line numbers" in menu "Preferences/Java/Decompiler" was active.

JD-Eclipse插�g + realignment 补丁让优雅的debug class 文�g成�ؓ可能�?br />
如果只是��Z��阅读class代码�Q�徏议不要用realignment 补丁�Q�这样会降低代码的可��L��（会多出大量的�I��Q?br />

Milo的�v�?/a> 2013-02-22 15:01 发表评论

一些项目中用到的mvn例子

Thu, 10 Jan 2013 05:33:00 GMT

mvn 执行外部命��o
命��o行模�?br />

mvn exec:exec -Dexec.executable=sh -Dexec.workingdir=./bin -Dexec.args=hello.sh

配置文�g形式

                                org.codehaus.mojo
                                exec-maven-plugin


                                                test-exec
                                                initialize

                                                        sh
                                                        ./bin

                                                                hello.sh



                                                        exec

mvn 生成java��目
生成骨架

mvn archetype:generate -DgroupId=com.abc.product -DartifactId=product -DpackageName=com.abc.product -DarchetypeArtifactId=maven-archetype-quickstart

转成eclipse能识别的java ��目

mvn eclipse:eclipse

导入eclipse 然后coding

mvn�q�行单元��试

                                org.apache.maven.plugins
                                maven-surefire-plugin
                                2.12.4

                                        pertest

                                                **/perftest/*.java



                                                        log4j.configuration
                                                        target/test-classes/log4j.properties

mvn�q�行code coverage�l�计

        org.codehaus.mojo
        emma-maven-plugin
        1.0-alpha-3
        true


        org.codehaus.mojo
        surefire-report-maven-plugin
        true

mvn生成javadoc

                                org.apache.maven.plugins
                                maven-javadoc-plugin
                                2.9

                                        private



                                                attach-javadocs

                                                        javadoc
                                                        test-javadoc

                                                site

Milo的�v�?/a> 2013-01-10 13:33 发表评论

关于java.library.path

Thu, 06 Dec 2012 03:05:00 GMT

最�q�项目要用JNI, 涉及到用java.library.path�q�个参数�Q�开始以为只要ldconfig能识别到的so文�gjava 一定能扑ֈ��Q�可惜�ƈ不是�q�样。�?br />要想java�E�序扑ֈ��׃�n库还是要在执行java�E�序的时候指定java.library.path�Q�用eclipse的话可以讄��如下�Q?br />

Properties->Run/Debug settings->Arguments->VM arguments
-----------------------------------------
-Djava.library.path=/home/miaoyachun/workspace/JNIC/Release

�q�个是传�l�的方式�Q�google了下有个tricky的方式让�E�序动态修改java.library.path

    private static void loadJNILibDynamically() {
        try {
            System.setProperty("java.library.path", System.getProperty("java.library.path")
                    + ":/home/miaoyachun/workspace/JNIC/Release/");
            Field fieldSysPath = ClassLoader.class.getDeclaredField("sys_paths");
            fieldSysPath.setAccessible(true);
            fieldSysPath.set(null, null);

            System.loadLibrary("JNIC");
        } catch (Exception e) {
            // do nothing for exception
        }
    }

事实上linux下还有个环境变量LD_LIBRARY_PATH�Q�如果lib能在�q�个path里找刎ͼ�java.library.path��׃��用配�|�了�Q�而且不需要关心lib之间依赖的问题。java.library.path在这斚w��弱很多�Q�比如lib依赖其他目录的lib�{��?img src ="http://www.tkk7.com/miaoyachun/aggbug/392529.html" width = "1" height = "1" />

Milo的�v�?/a> 2012-12-06 11:05 发表评论

Ubuntu上的alternatives

Fri, 26 Oct 2012 05:31:00 GMT

关于alternatives的用�?br />

alternatives --install /usr/bin/java java /opt/jdk1.5.0_22/bin/java 15000
alternatives --install /usr/bin/javac javac /opt/jdk1.5.0_22/bin/javac 15000
alternatives --config java
alternatives --config javac

最�q�切换桌面环境到ubuntu, 发现alternatives�q�个工具改名�?update-alternatives
用法�q�是一��L��。�?br />

Milo的�v�?/a> 2012-10-26 13:31 发表评论

用JNI从C传递结构体到JAVA

Fri, 12 Oct 2012 08:40:00 GMT

直接上C的实�?br />

typedef struct Foo {
    int len;
    char name[100];
} Foo_t;

JNIEXPORT jint JNICALL
Java_TestJNI_foo(JNIEnv *env, jobject obj, jobject fooObj) {

    Foo_t * bar = malloc(sizeof(Foo_t));
    jclass clazz;
    jfieldID fid;

    //init the bar data of C
    strcpy(bar->name, "Yachun Miao");
    bar->len = strlen(bar->name);

    // mapping bar of C to foo
    clazz = (*env)->GetObjectClass(env, fooObj);
    if (0 == clazz) {
        printf("GetObjectClass returned 0\n");
        return (-1);
    }
    fid = (*env)->GetFieldID(env, clazz, "len", "I");
    (*env)->SetLongField(env, fooObj, fid, bar->len);

    fid = (*env)->GetFieldID(env, clazz, "name", "Ljava/lang/String;");
    jstring name = (*env)->NewStringUTF(env, bar->name);
    (*env)->SetObjectField(env, fooObj, fid, name);

    free(bar);
    return 0;
}

对应的Java调用

public class Foo {
    protected int len;
    protected String name;
}

    private static native int foo(Foo fooObj);

    public static void main(String args[]) {
        System.loadLibrary("mylib");

        Foo foo = new Foo();
        foo(foo);
        System.out.println(foo.name);
        System.out.println(foo.len);

    }

参考链�?br />

http://www.steveolyo.com/JNI/JNI.html#CSTRCJ

http://docs.oracle.com/javase/6/docs/technotes/guides/jni/spec/types.html

Milo的�v�?/a> 2012-10-12 16:40 发表评论

Jetty SslSelectChannelConnector about file downloading

Wed, 18 Jul 2012 10:22:00 GMT

发现用curl从jetty服务器上download文�g的速度比较慢大概只�?M/s, 开始以为curl有默认的limit-rate�Q�设�|��ؓ1G以后发现�q�是慢�?br />然后开始怀疑是jetty server的问题。看SslSelectChannelConnector的responseBufferSize比较像，反复实验发现原来是由于headerBufferSize太小�?br /> 改�ؓ32K以后�Q?br />

        SslSelectChannelConnector connector = new SslSelectChannelConnector();

        connector.setRequestBufferSize(32768);

效果�Q?br />

curl -k https://USER:PASSWD@HOST:PORT/api/internal/file?filename=/path/to/file > /dest/to/file
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                             Dload     Upload   Total   Spent     Left   Speed
100  723M  100  723M    0     0   29.3M      0       0:00:24  0:00:24 --:--:-- 29.4M

ref: http://wiki.eclipse.org/Jetty/Howto/Configure_Connectors

Milo的�v�?/a> 2012-07-18 18:22 发表评论

maven project to eclipse java project

Wed, 27 Jun 2012 07:56:00 GMT

steps:

1. download maven project src code
2. cd project root dir & run "mvn eclipse:eclipse"
3. import it as eclipse java prject

step2 will generate .classpath & .project file

Milo的�v�?/a> 2012-06-27 15:56 发表评论

��目依赖分析工具

Wed, 13 Jun 2012 08:13:00 GMT

zane昨天推荐个项目依赖分析的工具: http://www.jboss.org/tattletale

JBoss Tattletale is a tool that can help you get an overview of the project you are working on
or a product that you depend on.

The tool will provide you with reports that can help you

* Identify dependencies between JAR files
* Find missing classes from the classpath
* Spot if a class/package is located in multiple JAR files
* Spot if the same JAR file is located in multiple locations
* With a list of what each JAR file requires and provides
* Verify the SerialVersionUID of a class
* Find similar JAR files that have different version numbers
* Find JAR files without a version number
* Find unused JAR files
* Identify sealed / signed JAR archives
* Locate a class in a JAR file
* Get the OSGi status of your project

使用�Ҏ��

java -Xmx512m -jar tattletale.jar [-exclude=]

[output-directory]

注意事项

tattletale只分析jar包之间的依赖�Q�需要自己把所有的class文�g打包攑օ�scan-directory�Q�然后把依赖的lib也放入同个目�?/span>

Milo的�v�?/a> 2012-06-13 16:13 发表评论

Java�q�程memory leak分析

Fri, 16 Mar 2012 01:45:00 GMT

参�?nbsp;jmap & jhat
通过分析heap中对象的数量�q�有大小可以定位哪个�c�d��了问题�?img src ="http://www.tkk7.com/miaoyachun/aggbug/372005.html" width = "1" height = "1" />

Milo的�v�?/a> 2012-03-16 09:45 发表评论

Program exception handling

Mon, 12 Mar 2012 08:35:00 GMT

1. ��量避免抛出异常
    异常是有代�h的，比如��量避免使用异常来实现流�E�控�?br />2. ��量处理异常
    有能力处理异常则处理掉，不然外层函数会篏�U�太多的异常
3. 处理不了则抛出异�?br />    自己问自己，�q�个异常能够处理么，不行的话直接抛出�Q�可以参考原�?
4. Throw early and catch late
    一般底层函��C��会处理异常，外层函数会根据上下文捕获异常�q�行处理或者�{�?br />5. 不要覆盖异常
6. try块不应该太大�Q�代码规范）
7. 函数抛出的异�怸�应该太多�Q�代码规范）

参�?br />

Milo的�v�?/a> 2012-03-12 16:35 发表评论