- android - 多次调用 OnPrimaryClipChangedListener
- android - 无法更新 RecyclerView 中的 TextView 字段
- android.database.CursorIndexOutOfBoundsException : Index 0 requested, 光标大小为 0
- android - 使用 AppCompat 时,我们是否需要明确指定其 UI 组件(Spinner、EditText)颜色
我正在尝试使用 Iginte Hibernate L2 缓存开发 Spring Boot 应用程序。
在启动 Spring Boot 应用程序之前,我运行我的服务器节点。当我尝试运行 Spring Boot 应用程序时,出现以下错误:
输出
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v1.5.3.RELEASE)
2018-11-28 18:14:50.291 INFO 20868 --- [ main] c.o.apache.ignite.learn.Application : Starting Application on DESKTOP-UNSVMQG with PID 20868 (C:\Users\patri\HibernateL2Cache\target\classes started by patri in C:\Users\patri\HibernateL2Cache)
2018-11-28 18:14:50.293 INFO 20868 --- [ main] c.o.apache.ignite.learn.Application : No active profile set, falling back to default profiles: default
2018-11-28 18:14:50.324 INFO 20868 --- [ main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@50a638b5: startup date [Wed Nov 28 18:14:50 CET 2018]; root of context hierarchy
2018-11-28 18:14:51.353 INFO 20868 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080 (http)
2018-11-28 18:14:51.365 INFO 20868 --- [ main] o.apache.catalina.core.StandardService : Starting service Tomcat
2018-11-28 18:14:51.366 INFO 20868 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/8.5.14
2018-11-28 18:14:51.463 INFO 20868 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2018-11-28 18:14:51.464 INFO 20868 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1142 ms
2018-11-28 18:14:51.565 INFO 20868 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean : Mapping servlet: 'dispatcherServlet' to [/]
2018-11-28 18:14:51.568 INFO 20868 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'characterEncodingFilter' to: [/*]
2018-11-28 18:14:51.569 INFO 20868 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2018-11-28 18:14:51.569 INFO 20868 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'httpPutFormContentFilter' to: [/*]
2018-11-28 18:14:51.570 INFO 20868 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'requestContextFilter' to: [/*]
2018-11-28 18:14:52.065 INFO 20868 --- [ main] j.LocalContainerEntityManagerFactoryBean : Building JPA container EntityManagerFactory for persistence unit 'default'
2018-11-28 18:14:52.074 INFO 20868 --- [ main] o.hibernate.jpa.internal.util.LogHelper : HHH000204: Processing PersistenceUnitInfo [
name: default
...]
2018-11-28 18:14:52.123 INFO 20868 --- [ main] org.hibernate.Version : HHH000412: Hibernate Core {5.0.12.Final}
2018-11-28 18:14:52.124 INFO 20868 --- [ main] org.hibernate.cfg.Environment : HHH000206: hibernate.properties not found
2018-11-28 18:14:52.125 INFO 20868 --- [ main] org.hibernate.cfg.Environment : HHH000021: Bytecode provider name : javassist
2018-11-28 18:14:52.159 INFO 20868 --- [ main] o.hibernate.annotations.common.Version : HCANN000001: Hibernate Commons Annotations {5.0.1.Final}
2018-11-28 18:14:52.248 INFO 20868 --- [ main] org.hibernate.dialect.Dialect : HHH000400: Using dialect: org.hibernate.dialect.MySQL5Dialect
2018-11-28 18:14:52.460 WARN 20868 --- [ main] ationConfigEmbeddedWebApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaAutoConfiguration.class]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
2018-11-28 18:14:52.536 INFO 20868 --- [ main] utoConfigurationReportLoggingInitializer :
Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled.
2018-11-28 18:14:52.543 ERROR 20868 --- [ main] o.s.boot.SpringApplication : Application startup failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaAutoConfiguration.class]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1628) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1081) ~[spring-context-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:856) ~[spring-context-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:542) ~[spring-context-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:737) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:370) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:314) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1162) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1151) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE]
at com.ontius.apache.ignite.learn.Application.main(Application.java:13) [classes/:na]
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.persistenceException(EntityManagerFactoryBuilderImpl.java:954) ~[hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:882) ~[hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:60) ~[spring-orm-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:353) ~[spring-orm-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:370) ~[spring-orm-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:359) ~[spring-orm-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1687) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1624) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]
... 16 common frames omitted
Caused by: org.hibernate.service.spi.ServiceException: Unable to create requested service [org.hibernate.engine.spi.CacheImplementor]
at org.hibernate.service.internal.AbstractServiceRegistryImpl.createService(AbstractServiceRegistryImpl.java:264) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:228) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:207) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
at org.hibernate.service.internal.SessionFactoryServiceRegistryImpl.getService(SessionFactoryServiceRegistryImpl.java:68) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:244) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:444) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:879) ~[hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
... 22 common frames omitted
Caused by: org.apache.ignite.IgniteIllegalStateException: Ignite instance with provided name doesn't exist. Did you call Ignition.start(..) to start an Ignite instance? [name=HibernateL2CacheGrid]
at org.apache.ignite.internal.IgnitionEx.grid(IgnitionEx.java:1383) ~[ignite-core-2.6.0.jar:2.6.0]
at org.apache.ignite.Ignition.ignite(Ignition.java:535) ~[ignite-core-2.6.0.jar:2.6.0]
at org.apache.ignite.cache.hibernate.HibernateAccessStrategyFactory.start(HibernateAccessStrategyFactory.java:112) ~[ignite-hibernate-core-2.6.0.jar:2.6.0]
at org.apache.ignite.cache.hibernate.HibernateRegionFactory.start(HibernateRegionFactory.java:92) ~[ignite-hibernate_5.1-2.6.0.jar:2.6.0]
at org.hibernate.internal.CacheImpl.<init>(CacheImpl.java:49) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
at org.hibernate.engine.spi.CacheInitiator.initiateService(CacheInitiator.java:28) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
at org.hibernate.engine.spi.CacheInitiator.initiateService(CacheInitiator.java:20) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
at org.hibernate.service.internal.SessionFactoryServiceRegistryImpl.initiateService(SessionFactoryServiceRegistryImpl.java:49) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
at org.hibernate.service.internal.AbstractServiceRegistryImpl.createService(AbstractServiceRegistryImpl.java:254) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
... 28 common frames omitted
Process finished with exit code 1
为了更好地理解我的代码,我在下面列出了相关代码片段。
缓存配置工厂
public class CacheConfigurationFactory {
public static List<CacheConfiguration> createCacheList() {
List<CacheConfiguration> cacheList = new ArrayList<CacheConfiguration>();
cacheList.add(createTransactionalCache("com.ontius.apache.ignite.learn.model.Person"));
cacheList.add(createAtomicCache("org.hibernate.cache.spi.UpdateTimestampsCache"));
cacheList.add(createAtomicCache("org.hibernate.cache.internal.StandardQueryCache"));
return cacheList;
}
private static CacheConfiguration createAtomicCache(String cacheName) {
CacheConfiguration cacheConfiguration = new CacheConfiguration();
cacheConfiguration.setCacheMode(CacheMode.PARTITIONED);
cacheConfiguration.setAtomicityMode(CacheAtomicityMode.ATOMIC);
cacheConfiguration.setWriteSynchronizationMode(CacheWriteSynchronizationMode.FULL_SYNC);
cacheConfiguration.setName(cacheName);
return cacheConfiguration;
}
private static CacheConfiguration createTransactionalCache(String cacheName) {
CacheConfiguration cacheConfiguration = new CacheConfiguration();
cacheConfiguration.setCacheMode(CacheMode.PARTITIONED);
cacheConfiguration.setAtomicityMode(CacheAtomicityMode.TRANSACTIONAL);
cacheConfiguration.setWriteSynchronizationMode(CacheWriteSynchronizationMode.FULL_SYNC);
cacheConfiguration.setName(cacheName);
return cacheConfiguration;
}
}
服务器配置工厂
public class ServerConfigurationFactory {
public static IgniteConfiguration createConfiguration() {
IgniteConfiguration igniteConfiguration = new IgniteConfiguration();
igniteConfiguration.setClientMode(false);
igniteConfiguration.setIgniteInstanceName("HibernateL2CacheGrid");
igniteConfiguration.setPeerClassLoadingEnabled(true);
TcpDiscoverySpi discoverySpi = new TcpDiscoverySpi();
TcpDiscoveryMulticastIpFinder ipFinder = new TcpDiscoveryMulticastIpFinder();
ipFinder.setAddresses(Arrays.asList("127.0.0.1:47500:47509"));
discoverySpi.setIpFinder(ipFinder);
igniteConfiguration.setDiscoverySpi(discoverySpi);
List<CacheConfiguration> cacheList = CacheConfigurationFactory.createCacheList();
igniteConfiguration.setCacheConfiguration(cacheList.toArray(new CacheConfiguration[cacheList.size()]));
return igniteConfiguration;
}
}
客户端配置工厂
public class ClientConfigurationFactory {
public static IgniteConfiguration createConfiguration() {
IgniteConfiguration igniteConfiguration = new IgniteConfiguration();
igniteConfiguration.setClientMode(true);
igniteConfiguration.setIgniteInstanceName("HibernateL2CacheGrid");
igniteConfiguration.setPeerClassLoadingEnabled(true);
TcpDiscoverySpi discoverySpi = new TcpDiscoverySpi();
TcpDiscoveryMulticastIpFinder ipFinder = new TcpDiscoveryMulticastIpFinder();
ipFinder.setAddresses(Arrays.asList("127.0.0.1:47500:47509"));
discoverySpi.setIpFinder(ipFinder);
igniteConfiguration.setDiscoverySpi(discoverySpi);
List<CacheConfiguration> cacheList = CacheConfigurationFactory.createCacheList();
igniteConfiguration.setCacheConfiguration(cacheList.toArray(new CacheConfiguration[cacheList.size()]));
return igniteConfiguration;
}
}
SessionFactory配置
@EnableAutoConfiguration
public class SessionFactoryConfiguration {
@Bean
public HibernateJpaSessionFactoryBean sessionFactory(EntityManagerFactory entityManagerFactory) {
HibernateJpaSessionFactoryBean hibernateJpaSessionFactoryBean = new HibernateJpaSessionFactoryBean();
hibernateJpaSessionFactoryBean.setEntityManagerFactory(entityManagerFactory);
return hibernateJpaSessionFactoryBean;
}
}
服务器节点启动
public class ServerNodeStartup {
public static void main(String[] args) {
Ignition.start(ServerConfigurationFactory.createConfiguration());
}
}
申请
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
@Bean
public IgniteSpringBean igniteInstance() {
IgniteSpringBean igniteSpringBean = new IgniteSpringBean();
igniteSpringBean.setConfiguration(ClientConfigurationFactory.createConfiguration());
return igniteSpringBean;
}
}
application.yml
spring:
application:
name: HibernateL2Cache
datasource:
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/demo_app?useSSL=false
username: root
password: demo
jpa:
properties:
hibernate:
show_sql: true
generate_statistics: true
cache:
use_query_cache: true
use_second_level_cache: true
region:
factory_class: org.apache.ignite.cache.hibernate.HibernateRegionFactory
org:
apache:
ignite:
hibernate:
ignite_instance_name: HibernateL2CacheGrid
default_access_type: READ_WRITE
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.ontius.apache.ignite.learn</groupId>
<artifactId>hibernate-l2-cache</artifactId>
<version>1.0-SNAPSHOT</version>
<name>HibernateL2Cache</name>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
<ignite.version>2.6.0</ignite.version>
</properties>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.3.RELEASE</version>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<!-- Apache Ignite -->
<dependency>
<groupId>org.apache.ignite</groupId>
<artifactId>ignite-core</artifactId>
<version>${ignite.version}</version>
</dependency>
<dependency>
<groupId>org.apache.ignite</groupId>
<artifactId>ignite-spring</artifactId>
<version>${ignite.version}</version>
</dependency>
<dependency>
<groupId>org.apache.ignite</groupId>
<artifactId>ignite-hibernate_5.1</artifactId>
<version>${ignite.version}</version>
</dependency>
<!-- MySQL -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.13</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
我想我必须在初始化entityManagerFactory之前在Spring Boot应用程序中启动ignite。但我不知道如何才能实现这一目标。
最佳答案
首先,您的地址
有一个拼写错误:127.0.0.1:47500:47509
应该是127.0.0.1:47500..47509
。
其次,您有两种选择将 Hibernate L2 Cache 链接到 Ignite - 在 Hibernate 初始化之前在同一 JVM 中手动启动 Ignite 节点或让 Hibernate 自动启动。
由于您使用的是 Spring Boot,并且 Ignite 始终在 Spring 上下文中最后启动,因此采用第二种方法可能会更容易。
要启用自动 Ignite 启动,您需要将 org.apache.ignite.hibernate.grid_config 属性设置为 Ignite XML 配置的路径。不幸的是,这里似乎不能使用基于Java的配置,只能使用XML。您可以将客户端配置转换为 XML,将其放入 META-INF
下的资源中,例如 META-INF/ignite-client.xml
,然后引用它(现在没有 META-INF
) - org.apache.ignite.hibernate.grid_config: ignite-client.xml
。您还应该删除客户端应用程序中的 ignite_instance_name
属性(因为它被 grid_config
覆盖)和 Ignite bean(因为它现在由 Hibernate 启动)。
关于java - Apache Ignite Hibernate L2 缓存与 Spring Boot,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/53525023/
话说,尾部的++在这里没有实际作用? 最佳答案 l+l++ 未定义。您的表达式中没有序列点来分隔对 l 的访问和后增量。它可以做任何事情,包括具有与 l+l 相同的效果。 编辑:问题和答案在 Why
我正在研究成员资格算法,我正在研究这个特定问题,该问题说明如下: 展示一种算法,给定任何常规语言 L,确定 L 是否 = L* 所以,我的第一个想法是,我们有 L*,它是 L 的 Kleene 星并确
我试图弄清楚如何使用 Javascript 生成一个随机 11 个字符串,该字符串需要特定的字母/数字序列,以及位置。 ----------------------------------------
我一直在 LinqPad 中试验查询。我们有一个表 Lot,其中有一列 Side char(1)。当我编写 linq to sql 查询 Lots.Where(l => l.Side == 'A')
这个问题在这里已经有了答案: Iterate over all pairs of consecutive items in a list [duplicate] (7 个答案) 关闭 7 年前。 假
列表 ['a','a #2','a(Old)'] 应变为 {'a'} 因为 '# ' 和 '(Old)' 将被删除,并且不需要重复项列表。我努力用生成器开发列表理解,并决定这样做,因为我知道它会起作用
我正在为蛇和梯子制作一 block 板,到目前为止,我已经按降序打印了板。但是,我需要以正确的方式打印电路板。 编辑“螺旋下降”意味着 100...91 81...90 80...71 ...
字符串“Hello\n”等于 {'H','e','l','l','o','\','n','\0'} 或 {'H','e','l','l','o','\n','\0'}? 是否在字符串定义中添加转义序列
这个问题在这里已经有了答案: Different behaviour for list.__iadd__ and list.__add__ (3 个答案) 关闭 8 年前。 ls = [1,2,3]
当我在编写一个程序时,我在我的代码中看到了一个奇怪的行为。这是我所看到的。 >>> l = [1,2,3,4,5,6,7,8] >>> g = [] >>> for i in l: ... g
我明白了what a Y Combinator is , 但我不明白这个来自 Wikipedia page 的“新颖”组合子的例子: Yk = (L L L L L L L L L L L L L
Exception ParseException is not compatible with throws clause in Comparator.compare(L, L). 我在java 6上
期望的输出 我想要一个函数返回一个列表,这样,给定一个“困惑的”列表 l,每个元素都是 l 对应元素的索引,如果 l 已排序。 (抱歉,我想不出更简单的说法。) 示例 f([3,1,2]) = [2,
你好,我正在查看“假设一个排序数组在你事先不知道的某个枢轴旋转。(即 0 1 2 4 5 6 7 可能变成 4 5 6 7 0 1 2)”这个问题的 C++ 解决方案。你如何有效地在旋转数组中找到一个
让我们考虑这个简单的例子: import numpy as np a=np.arange(90) a=a.reshape(6,3,5) 我想得到一个数组 b形状 (6*5,3+1=4) 与 b[0:6
我正在编写一个 q 脚本,它在特定路径中加载一个数据库并对其进行一些处理。 db 的位置目前在脚本中是硬编码的,但我想将 db 路径作为参数传递并让它从变量中的路径加载。 目前它看起来像这样: q)
为什么我收到错误 Device: (3:9741) (0,l.useLinkBuilder) is not a function。 (在 '(0,l.useLinkBuilder)()' 中,'(0,
我有 ADT 版本 23.0.4 并安装了 Android 5.0 的 SDK 平台。 我读到 Android 5.0 Lolipop 的 API 级别为 21。但是在 Eclipse 的“新建应用程
我在 Google Play Store 中实现了一个抽屉导航,我想在 DrawerLayout 中设置列 TableView 的选定项目。但是后来发现在touch模式下无法选中item,有一个i
作为 C++ 的新手,我基本上有一个关于 g++ 编译器的问题,尤其是库的包含。考虑以下生成文件: CPPFLAGS= -I libraries/boost_1_43_0-bin/include/ -
我是一名优秀的程序员,十分优秀!