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Kotysh's questions

Martin Hope
Kotysh
Asked: 2020-11-21 22:19:37 +0800 CST
  • 1

我想做一个每三天运行一次的 cron 表达式，如果你这样做0 8 */3 * *，这意味着每个月的第三天 8:00 都会触发一个计时器，我希望如果我设置一个表达式，那么它将每 3 天准确运行一次，例如，从 1 月 23 日开始，因此，接下来的几天：26 日 29 日和 2 月 1 日。这可以做到吗？怎么做？有一个想法是在几分钟内完成，即*/4800 * * * *理论上意味着每 3 天 8:00 触发一次

linux
Martin Hope
Kotysh
Asked: 2020-10-10 18:50:08 +0800 CST
  • 0

我有管理服务

private com.ibm.websphere.management.AdminService adminService = AdminServiceFactory.getAdminService();

有了它，我可以获得有关服务器的不同信息，但是我无法获得有关已安装应用程序的信息（名称，状态是否正在运行等），我认为我需要使用invoke方法，但基于文档，目前还不是很清楚如何做到这一点：

https://www.ibm.com/support/knowledgecenter/SS7JFU_8.5.5/com.ibm.websphere.javadoc.doc/web/apidocs/com/ibm/websphere/management/AdminService.html

我在网上没有找到类似的例子，请告诉我这是怎么回事

java
Martin Hope
Kotysh
Asked: 2020-06-07 22:47:02 +0800 CST
  • 1

有这样的要求

select * from
 (select * from
  (select a.*, rownum rnum from
   (select * from dimax)a)
 where rownum <= 5)
where rnum > 2

就地dimax的表总是不同的，也就是说，我有一百个表，它们的列不同，不知道我将在查询中使用哪个表。一切都会正常工作，但其中一个表可能与 rownum 别名匹配，然后查询将失败。如何解决这个问题并在未知表中选择所需的行？

sql
Martin Hope
Kotysh
Asked: 2020-04-12 15:30:48 +0800 CST
  • 1

大家好！）我想知道是否可以使用 JavaMail API 以某种方式选择邮件中的消息，例如，使用某些用户，例如使用 example@example.ex，并获取服务器上的所有通信? 也就是说，我希望收到我发送给他的所有消息以及他发送给我的所有消息。除了通过此 API 发送消息外，我没有找到任何具体示例。是否有这种可能性，如果有，我应该使用什么或有某种教程？

java
Martin Hope
Kotysh
Asked: 2020-01-31 15:05:48 +0800 CST
  • 0

众所周知，如果在-128到127的范围内通过==比较2个Integer类型的对象，那么它们会比较这些对象中的值，如果数字不在这个范围内，那么引用到将比较对象。问题是是否可以增加这个池的大小，如果可以，怎么做？通过 == 来比较和更大的数字，比如变成这样：

Integer a = 800;
Integer b = 800;
System.out.println(a == b); //true
java
Martin Hope
Kotysh
Asked: 2020-11-29 21:32:11 +0800 CST
  • -1

我有这个网址：

bookManag/book?name=world and war #2&field=1

我传入名称参数 - world and war #2 问题是在 # 之后所有内容都被切断并且下一个字段参数没有出现。好的，我找到了摆脱这种情况的方法并将哈希替换为 %23

bookManag/book?name=world and war %232&field=1

但主要问题不是这个，我试图通过 ResponseEntity 得到响应

    String url = "http://localhost:8081/bookManag/book?name=world and war %232&field=1";
    org.springframework.http.ResponseEntity result = restTemplate.exchange(url, HttpMethod.GET, entity, getRespType(), params);

之后，spring 内部已经发生错误，而不是我正确的 url，spring 将其重新制作为

"http://localhost:8081/bookManag/book?name=world and war %20%25232&field=1"

用 %2523 替换 %23 最终会给出错误的结果。如何解决这个问题？

java
Martin Hope
Kotysh
Asked: 2020-10-26 06:35:49 +0800 CST
  • 0

使用 JUnit 我测试数据库查询，如果我单独运行测试，那么一切正常，但如果我开始使用 maven 构建项目，那么由于此错误，没有任何测试通过：

Oct 26, 2018 1:33:09 AM org.apache.tomcat.jdbc.pool.ConnectionPool init
SEVERE: Unable to create initial connections of pool.
java.sql.SQLException: Unable to load class: oracle.jdbc.driver.OracleDriver from ClassLoader:sun.misc.Launcher$AppClassLoader@6bc7c054;ClassLoader:sun.misc.Launcher$AppClassLoader@6bc7c054
    at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:283)
    at org.apache.tomcat.jdbc.pool.PooledConnection.connect(PooledConnection.java:203)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.createConnection(ConnectionPool.java:738)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:670)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.init(ConnectionPool.java:482)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.<init>(ConnectionPool.java:154)
    at org.apache.tomcat.jdbc.pool.DataSourceProxy.pCreatePool(DataSourceProxy.java:118)
    at org.apache.tomcat.jdbc.pool.DataSourceProxy.createPool(DataSourceProxy.java:107)
    at org.apache.tomcat.jdbc.pool.DataSourceProxy.getConnection(DataSourceProxy.java:131)
    at ru.dmitriikotiashov.dao.jdbc.ConnectionPool.getConnection(ConnectionPool.java:21)
    at ru.dmitriikotiashov.test.dao.ConnectionTest.getConnection(ConnectionTest.java:23)
    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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:365)
    at org.apache.maven.surefire.junit4.JUnit4Provider.executeWithRerun(JUnit4Provider.java:273)
    at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:238)
    at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:159)
    at org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:379)
    at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:340)
    at org.apache.maven.surefire.booter.ForkedBooter.execute(ForkedBooter.java:125)
    at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:413)
Caused by: java.lang.ClassNotFoundException: Unable to load class: oracle.jdbc.driver.OracleDriver from ClassLoader:sun.misc.Launcher$AppClassLoader@6bc7c054;ClassLoader:sun.misc.Launcher$AppClassLoader@6bc7c054
    at org.apache.tomcat.jdbc.pool.ClassLoaderUtil.loadClass(ClassLoaderUtil.java:56)
    at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:272)
    ... 35 more
Caused by: java.lang.ClassNotFoundException: oracle.jdbc.driver.OracleDriver
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:348)
    at org.apache.tomcat.jdbc.pool.ClassLoaderUtil.loadClass(ClassLoaderUtil.java:38)
    ... 36 more

我无法弄清楚问题是什么，请告诉我如何解决？

java
Martin Hope
Kotysh
Asked: 2020-10-19 23:20:45 +0800 CST
  • 3

有一个接口

package ioc.primary_annotation;

public interface Animal {

    void display();

}

两个类实现它

package ioc.primary_annotation;

import org.springframework.stereotype.Component;

@Component("kitty")
public class Cat implements Animal {
    public void display() {
        System.out.println("Cat.display");
    }
}

和

package ioc.primary_annotation;

import org.springframework.stereotype.Component;

@Component("doggi")
public class Dog implements Animal {
    public void display() {
        System.out.println("Dog.display");
    }
}

有一个配置类

package ioc.primary_annotation;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan(basePackages = "ioc.primary_annotation")
public class AppConfig {
}

和服务

package ioc.primary_annotation;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;;
import org.springframework.stereotype.Service;

@Service
public class AnimalService {

    @Autowired
    @Qualifier("kitty")
    private Animal animal;

    public AnimalService() {
    }

    public Animal getAnimal() {
        return animal;
    }

    public void setAnimal(Animal animal) {
        this.animal = animal;
    }
}

所有这些都应该在 main 方法中起作用

package ioc.primary_annotation;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class PrimaryMain {

    public static void main(String[] args) {

        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
        Animal animal = applicationContext.getBean(Animal.class);
        animal.display();

    }

}

但它不起作用，抛出异常。

Exception in thread "main" org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'ioc.primary_annotation.Animal' available: expected single matching bean but found 2: kitty,doggi

问题是为什么它不起作用，因为我通过限定符指出了我应该使用哪个 bean？如果我在 Cat 或 Dog 类上方指定 @Primary 注释，那么一切都会神奇地开始工作，请告诉我这里有什么神奇之处，在此先感谢 :)

java
Martin Hope
Kotysh
Asked: 2020-06-18 20:04:26 +0800 CST
  • 0

大家好！我有这样的问题

@RequestMapping(value = "/createrobot", method = RequestMethod.POST)
public Robot createRobot(
        @RequestParam(value="id", required = false, defaultValue = "-") String id,
        @RequestParam(value="name", required = false, defaultValue = "-") String name,
        @RequestParam(value="age", required = false, defaultValue = "-") String age,
        @RequestBody Robot robot){

    return new Robot(1, "Maks", "456");

}

我在 POSTMAN http://localhost:8081/supercontroller/createrobot中发出请求

我通过 Json

{
    "id": 78,
    "name": "-",
    "age": "-"
}

发生错误：

{
    "timestamp": "2018-06-18T11:57:02.825+0000",
    "status": 500,
    "error": "Internal Server Error",
    "message": "Type definition error: [simple type, class ru.asdf.Robot]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `ru.asdf.Robot` (no Creators, like default construct, exist): cannot deserialize from Object value (no delegate- or property-based Creator)\n at [Source: (PushbackInputStream); line: 2, column: 5]",
    "path": "/supercontroller/createrobot"
}

我看到问题出在反序列化中，我该如何解决？有一个机器人实体

public class Robot {

    Integer id;
    String name;
    String age;

    public Robot(int id, String name, String age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }
}

使用什么注释？

java
Martin Hope
Kotysh
Asked: 2020-05-18 14:58:31 +0800 CST
  • 0

我正在尝试在 TortoiseSVN 中创建补丁，但是我无法提交已删除的文件，即当我运行 create patch 命令时，补丁中只显示已删除的文件，并且只有已添加或更改的文件结束在补丁中。帮助解决问题。我通过右键单击项目文件夹并选择创建补丁命令来制作补丁。提前致谢！

svn
Martin Hope
Kotysh
Asked: 2020-04-23 00:41:18 +0800 CST
  • 0

大家好！我需要用 Racket 语言实现一个函数，该函数用一个变量计算简单数学表达式的导数。该函数必须有 2 个参数 - 具有 Scheme 语言标准语法的数学表达式，包含数字、原子（常量和变量）和函数 +、-、*、/、expt（数字 e 的取幂）。第二个参数是需要区分的变量。表达式中的其他字符被视为常量。
也许有人遇到过类似的问题并且知道如何解决或从哪里开始？或者也许有一些文章专门讨论函数式语言的差异化。我在谷歌上搜索过，找不到类似的东西。对函数式语言中的算法感兴趣，可以是 Lisp、Scheme

lisp
Martin Hope
Kotysh
Asked: 2020-03-19 14:48:47 +0800 CST
  • 0

有一个关于Java增量工作的问题，我无法理解他在这些表达式中如何考虑它的逻辑：

    int a = 5;
    int b = 5;
    int c = 5;
    int d = 5;
    int e = 5;
    int f = 5;

    a += a++; //10
    b += b++ + ++b + b++; //24
    c = c++ + c++; //11
    d = d++ + ++d + d++ + ++d; //28
    e += e++ + ++e + e++ + ++e; //33
    f = f++; //5

最重要的是带有变量aand的表达式f，我想了解它在 JVM 中是如何工作的

java
Martin Hope
Kotysh
Asked: 2020-01-25 05:31:42 +0800 CST
  • 0

想把log4j连接到java ee，但是怎么都实现不了，不明白是什么问题，或者一开始就没有正确设置日志

通过 maven 我在 pom.xml 中连接库我添加 log4j

    <dependencies>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    </dependencies>

log4j.xml 在资源中

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j='http://jakarta.apache.org/log4j/'
                     debug="true">

    <appender name="fileAppender" class="org.apache.log4j.RollingFileAppender">
        <param name="maxFileSize" value="5KB"/>
        <param name="maxBackupIndex" value="4"/>
        <param name="file" value="loggi/logfileDAO.log"/>
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern"
                   value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1} - %m%n"/>
        </layout>
    </appender>

    <category name="ru.dmitriykotyshov.DAO">
        <!--all, trace, debug, info, warn, error, fatal-->
        <priority value="info"/>
        <appender-ref ref="fileAppender"/>
    </category>

</log4j:configuration>

我开始写日志并出现错误

log4j:ERROR Could not parse url [file:/C:/Users/Дмитрий/IdeaProjects/projectTrainTicket/out/artifacts/projectTrainTicket/WEB-INF/classes/log4j.xml].
com.sun.org.apache.xerces.internal.util.URI$MalformedURIException: Path contains invalid character: Д
    at com.sun.org.apache.xerces.internal.util.URI.initializePath(URI.java:1109)
    at com.sun.org.apache.xerces.internal.util.URI.initialize(URI.java:582)
    at com.sun.org.apache.xerces.internal.util.URI.<init>(URI.java:335)
    at com.sun.org.apache.xerces.internal.util.URI.<init>(URI.java:298)
    at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.expandSystemIdStrictOff1(XMLEntityManager.java:2221)
    at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.expandSystemId(XMLEntityManager.java:2053)
    at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.resolveEntityAsPerStax(XMLEntityManager.java:968)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$DTDDriver.dispatch(XMLDocumentScannerImpl.java:1152)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$DTDDriver.next(XMLDocumentScannerImpl.java:1045)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:959)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:602)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:505)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:841)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:770)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
    at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:243)
    at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:339)
    at org.apache.log4j.xml.DOMConfigurator$2.parse(DOMConfigurator.java:769)
    at org.apache.log4j.xml.DOMConfigurator.doConfigure(DOMConfigurator.java:871)
    at org.apache.log4j.xml.DOMConfigurator.doConfigure(DOMConfigurator.java:778)
    at org.apache.log4j.helpers.OptionConverter.selectAndConfigure(OptionConverter.java:526)
    at org.apache.log4j.LogManager.<clinit>(LogManager.java:127)
    at org.apache.log4j.Logger.getLogger(Logger.java:117)
    at ru.dmitriykotyshov.GetRoute.<clinit>(GetRoute.java:26)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at java.lang.Class.newInstance(Class.java:442)
    at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:114)
    at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1133)
    at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:853)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:135)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:962)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1115)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2555)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2544)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)
log4j:WARN No appenders could be found for logger (ru.dmitriykotyshov.GetRoute).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.

如何解决此问题或如何在 java ee 中连接日志？

java-ee
Martin Hope
Kotysh
Asked: 2020-01-06 17:42:26 +0800 CST
  • 1

无法连接到oracle数据库

Class.forName("oracle.jdbc.driver.OracleDriver");
Connection connection = null;
connection = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe","dima","123456");
connection.close();

抛出异常，不知道如何正确指定url地址

Exception in thread "main" java.sql.SQLException: ORA-00604: error occurred at recursive SQL level 1
ORA-12705: Cannot access NLS data files or invalid environment specified

    at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:447)
    at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:389)
    at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:382)
    at oracle.jdbc.driver.T4CTTIfun.processError(T4CTTIfun.java:675)
    at oracle.jdbc.driver.T4CTTIoauthenticate.processError(T4CTTIoauthenticate.java:448)
    at oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:513)
    at oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:227)
    at oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:383)
    at oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:776)
    at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:432)
    at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:553)
    at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:254)
    at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32)
    at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:528)
    at java.sql.DriverManager.getConnection(DriverManager.java:664)
    at java.sql.DriverManager.getConnection(DriverManager.java:247)
    at ru.mypackage.databaseConnection.Main.main(Main.java:20)

Process finished with exit code 1

Oracle 安装在本地服务器上

连接名称 - MyServerConnection 连接详情 - dima@//localhost:1521/xe

java
Martin Hope
Kotysh
Asked: 2020-12-12 05:28:10 +0800 CST
  • 0

大家好！需要从双端队列中删除元素。我使用另一个双端队列将所有元素推送到那里，除了被删除的元素，从而达到预期的结果，代码如下：

int main(){

        deque<int> list1;

        for (int i=0; i<10; i++){

            list1.push_back(i);

        }

        deque<int> list2;

        int deleteElement = 5;

        for (int i=0; i<list.size(); i++){

            if (list1[i] != deleteElement){
                list2.push_back(list1[i]);
            }

        }

}

但这需要很长时间，因为我将除被删除的元素之外的所有元素复制到另一个双端队列。我的问题是，有没有更优雅的方法从双端队列中间删除一个元素？

c++
Martin Hope
Kotysh
Asked: 2020-11-22 23:38:21 +0800 CST
  • 0

有一个用于向邮件发送消息的代码，如果您通过 main 方法而不是在服务器上运行它，那么一切正常并且消息会发送到邮件

  import java.util.Properties;
    import javax.mail.Message;
    import javax.mail.MessagingException;
    import javax.mail.PasswordAuthentication;
    import javax.mail.internet.*;
    import javax.mail.*;

    public class MainClass {

        public static void main(String[] args) {

            Properties p = new Properties();
            p.put("mail.smtp.host", "smtp.yandex.ru");
            p.put("mail.smtp.socketFactory.port", 465);
            p.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
            p.put("mail.smtp.auth", "true");
            p.put("mail.smtp.port", 465);




            Session s = Session.getInstance(p,

                    new javax.mail.Authenticator(){


                        protected PasswordAuthentication getPasswordAuthentication(){

                            return new PasswordAuthentication("mailOtpravitely@mail.ru", "passwordOtpravitely");

                        }


                    }
            );


            Message message = new MimeMessage(s);
            try {
                message.setFrom(new InternetAddress("mailOtpravitely@mail.ru"));
                message.setRecipient(Message.RecipientType.TO, new InternetAddress("mailPolychately@yandex.ru"));
                message.setSubject("Тема письма");
                message.setText("Сообщение в письме");

                Transport.send(message);

                System.out.println("Письмо успешно отправлено");

            } catch (MessagingException e) {
                System.out.println("Письмо не отправилось");
                e.printStackTrace();
            }

        }

    }

但是，如果我使用此代码在 TomCat 中创建一个 servlet，则会发生错误并且服务器无法启动：

SEVERE: ContainerBase.addChild: start: 
org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:162)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:1015)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:991)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:652)
    at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1899)
    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.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:301)
    at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
    at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
    at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:618)
    at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:565)
    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.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:301)
    at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
    at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
    at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1468)
    at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:76)
    at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1309)
    at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1401)
    at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:829)
    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 sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:324)
    at sun.rmi.transport.Transport$1.run(Transport.java:200)
    at sun.rmi.transport.Transport$1.run(Transport.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:568)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:683)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NoClassDefFoundError: javax/mail/MessagingException
    at java.lang.Class.getDeclaredFields0(Native Method)
    at java.lang.Class.privateGetDeclaredFields(Class.java:2583)
    at java.lang.Class.getDeclaredFields(Class.java:1916)
    at org.apache.catalina.util.Introspection.getDeclaredFields(Introspection.java:106)
    at org.apache.catalina.startup.WebAnnotationSet.loadFieldsAnnotation(WebAnnotationSet.java:270)
    at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:139)
    at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:65)
    at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:417)
    at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:891)
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:388)
    at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5519)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
    ... 42 more
Caused by: java.lang.ClassNotFoundException: javax.mail.MessagingException
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1892)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1735)
    ... 56 more

ноя 22, 2017 6:22:47 PM org.apache.tomcat.util.modeler.BaseModelMBean invoke
SEVERE: Exception invoking method manageApp
java.lang.IllegalStateException: ContainerBase.addChild: start: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[]]
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:1019)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:991)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:652)
    at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1899)
    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.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:301)
    at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
    at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
    at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:618)
    at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:565)
    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.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:301)
    at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
    at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
    at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1468)
    at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:76)
    at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1309)
    at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1401)
    at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:829)
    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 sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:324)
    at sun.rmi.transport.Transport$1.run(Transport.java:200)
    at sun.rmi.transport.Transport$1.run(Transport.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:568)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:683)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

ноя 22, 2017 6:22:47 PM org.apache.tomcat.util.modeler.BaseModelMBean invoke
SEVERE: Exception invoking method createStandardContext
javax.management.RuntimeOperationsException: Exception invoking method manageApp
    at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:309)
    at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
    at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
    at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:618)
    at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:565)
    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.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:301)
    at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
    at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
    at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1468)
    at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:76)
    at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1309)
    at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1401)
    at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:829)
    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 sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:324)
    at sun.rmi.transport.Transport$1.run(Transport.java:200)
    at sun.rmi.transport.Transport$1.run(Transport.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:568)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:683)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalStateException: ContainerBase.addChild: start: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[]]
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:1019)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:991)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:652)
    at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1899)
    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.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:301)
    ... 33 more

看不懂怎么回事，牺牲了映射之类的东西，万事大吉，我把代码放在doPost方法里自然没有main方法

java