Articles
Advanced Java

Basic syntax of python classes and objects

Two very important concepts of object-oriented programming: classes and objects.Objects are the core of object-oriented programming. In the process of using objects, in order to abstractly define a group of objects with common characteristics and behaviors, another new concept-class is proposed.My study notes are tested based on the python2 version.Define a classclass person: age=10 #The following sex will report an error if it is not initialized #sex name="intsmaze" def getPersonInfo(self): pri

... Christopher
schedule 4 min read
Advanced Java

JAVA's POI operation Excel

1.1 Introduction to ExcelAn excel file is a workbook, multiple worksheets can be created in a workbook, and a worksheet contains multiple cells, and these cells are composed of columns and rows. In capital English letters, there are 26 columns starting from A to Z, then 26 columns from AA to AZ, and then 26 columns from BA to BZ, and so on. Rows are represented by numbers, for example; A3 represents the third row and first column, and E5 represents the fifth row and fifth column.1.2 POI toolkitT

... Miles
schedule 4 min read
Advanced Java

Introduction to the feature preview of each version of Kafka0.8--0.11

Kafka-0.8.2 new features The producer no longer distinguishes between synchronous (sync) and asynchronous (async), all requests are sent asynchronously, which improves client efficiency. The producer request will return a response object, including the offset or error message. This asynchronously sends messages in batches to the kafka broker node, thus reducing the overhead of server-side resources. The network communication between the new producer and all servers is asynchronous. In the ack=-1

... Cora
schedule 10 min read
Advanced Java

RPC turned out to be Socket-service dynamic registration, service routing, load balancing evolution from RPC framework to dubbo

Preface: RPC is to use socket to tell the server which method of your class I want to call and get the result of processing. Service registration and routing is the use of third-party storage media to store service information for service consumers to call. However, we do it ourselves to write a rpc function from 0 and implement service registration, dynamic online and offline, service routing, and load balancing.Understand the principle of RPC in one sentence RPC stands for remote procedure ca

... Kaylee
schedule 16 min read
Advanced Java

Analysis of the constant change of the key value in a call of the reduce method in MapReduce and source code analysis

Abstract: In mapreduce, execute reduce (KEYIN key, Iterable<VALUEIN> values, Context context), call the reduce method once, and when iterating the value set, it is found that the value of the key is also constantly changing. This is because the address of the key will change internally. Constantly changing with the iteration of value. Sequence: We know that every time the reduce method is executed, we will iterate the iterator of value through the for loop. If the key is a bean, when the

... Henry
schedule 11 min read
Advanced Java

Redis master-slave, sentinel recall manual

redis master-slave The opening of persistence has nothing to do with whether the master-slave cluster takes effect Slave Server also completes data synchronization in a non-blocking manner. During synchronization, if a client submits a query request, Redis will return the data before synchronization (note that the first synchronization will block).The working principle of Replication:If the link between Master and Slave is disconnected, Slave can automatically reconnect to Master, but after the

... Grayson
schedule 7 min read
Core Java

Introduction and application of druid

What is Druid?Druid is first of all a database connection pool. Druid is currently the best database connection pool. It surpasses other database connection pools in terms of functionality, performance, and scalability, including DBCP, C3P0, BoneCP, Proxool, and JBoss DataSource.Druid has deployed more than 600 applications in Alibaba, and has been rigorously tested in a large-scale production environment for more than a year.At the same time, Druid is not only a database connection pool, it inc

... Emily
schedule 3 min read
Core Java

solr

Solr research summaryDevelopment typeFull-text search related developmentSolr version4.2document contentThis article introduces the use of Solr's functions and related precautions; mainly includes the following: environment construction and debugging; introduction of two core configuration files; maintenance index; query index, and highlighting, spelling check, and search suggestions that can be applied in the query , Group statistics, pinyin search and other functions.versionAuthor/EditordateV1

... Kaylee
schedule 70 min read
Core Java

Simple factory pattern of design pattern (1)

Simple factory patternBasic definition:The simple factory pattern is also called the static factory method, which belongs to the creational pattern. In the simple factory pattern, you can return instances of different classes according to the passed parameters. The simple factory pattern defines a class, which is specifically used to create instances of other classes, and these created classes have a common parent class.Mode structure:1. Factory: Factory role. A factory dedicated to creating ins

... Serenity
schedule 3 min read
Java Back End Development

Spring service customization

Summary of the problem​ We all know how to use Spring for bean management. If there are two implementation classes of the same interface, use @Autowiredannotations directly to implement bean injection, and an exception will be reported at startup. Our usual practice is to use @Resourceannotations to implement the name of the bean. However, using @Resourceannotations is similar to hard coding. If we want to modify the specific implementation of the interface, we must modify the code. Suppose that

... Weston
schedule 11 min read
Java Back End Development

Linux Exploration Road 1---CentOS entry notes finishing

PrefaceLast time I went with the operation and maintenance side to install the internal environment, and found that the linux command is still not very skilled. Especially the user authority assignment and shortcut operations under vi. So I decided to install a CentOS virtual machine locally, and then I would learn some common Linux commands every day when I had time.As a little white officially entered the pit of CentOS, so there was a CentOS exploration series. I will continue to update accord

... Bradley
schedule 8 min read
Java Back End Development

How to choose log components in web projects (SLF4J, Log4J2, logback)

One: Introduction to SLF4J, Log4J2, logback, and Apache log4j componentsslf4j translates as a simple log facade, which is an abstraction of the log framework. Both LogBack and Log4j are open source diary tool libraries. LogBack is an improved version of Log4j, which has more features than Log4j and also brings great performance improvements.Log4j2 is an open source project of Apache. By using Log4j2, we can control the delivery of log information; we can also control the output format of each lo

... Alyssa
schedule 10 min read
Java Back End Development

JavaWeb and JavaEE Naming Rules (Specifications)

Purpose: to achieve standardization in the coding process, and to develop good behavior habits in future program developmentI recently made a system. After I finished it, I found that the naming was not standardized enough, so I wanted to standardize the naming, so as to make the project directory more standardized and tidy. I found the detailed naming convention blog post on the Internet. However, some naming conventions are no longer suitable. Based on the reference to the blog post, the revis

... Abraham
schedule 11 min read
Java Back End Development

Pagehelper does not paging several solutions

I recently worked on a project and used the plug-in. I encountered some problems. Share the solutions here.Question one:pagehelper has no effect, it has not been able to paging problemSolution-Refer to the solution of other bloggers' blogs: http://blog.csdn.net/linxingliang/article/details/52566881Question 2:Pagehelper sometimes has an effect, sometimes it has no effectI encountered this problem in the project, and I have been looking for it for a long time.The solution is:inside pagehelperPageH

... Christopher
schedule 2 min read
Java Back End Development

Docker--docker ps command and result analysis

Detailed command Meaning: List container related information Format: docker ps [options] parameter list: parameterExplanationNo parametersShow running containers by default-aShow all containers, including those that are not running-fFilter the displayed content based on conditions--formatSpecify the template file for the return value-lShow recently created containers-nList recently created n containers--no-truncDo not truncate output-qSilent mode, only the container ID is displayed-sShow total

... Adriana
schedule 2 min read
Java Web Development

idea+mybatis+maven main测试

Project structurepom file<?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.bdqn</groupId> <artifactId>ssmDemo</artifactId> <version>1.0-SNAPSHOT</version> <packaging>war</packaging> <

... Kaylee
schedule 8 min read
Java Web Development

idea+mybatis The error may exist in com/XXXX/dao/UserDaoMapper.xml

The error message is as followsException in thread "main" org.apache.ibatis.exceptions.PersistenceException: ### Error building SqlSession. ### The error may exist in com/XXXX/dao/UserDaoMapper.xml ### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: java.io.IOException: Could not find resource com/bdqn/dao/UserDaoMapper.xml at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:23) at org.apache.ibatis.session.SqlSe

... Patrick
schedule 1 min read
Java Web Development

nexus build maven private server

download link https://www.sonatype.com/download-oss-sonatypeUnzip after downloadingShift+right click in the bin directoryClick here to execute the command lineinput the commandEnter in the address bar: http://localhost:8081Just see the following pageClick the place pointed by the arrow to log in: account admin password admin123Click on the arrow to show the type in the boxtype represents the warehouse type:Type purpose hosted means the current developer uploads, including snapshots snapshot vers

... Silas
schedule 10 min read
Java Web Development

springcloud config分布式配置中心 实现动态路由分布式配置中心(configServer)zuul动态路由网关

Distributed Configuration Center (configServer) pom dependency<!--spring-cloud integration config-server --> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-config-server</artifactId> <version>2.1.2. RELEASE</version> </dependency> <!-- SpringBoot integrates eureka client--> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-eureka

... Jameson
schedule 3 min read
Java Web Development

The zuul gateway returns parameters in the filter Chinese garbled zuul gateway configuration file: filter code startup class

Zuul gateway configuration file: Chinese garbled characters are configured in the configuration file ##Handle Chinese garbledspring: http: encoding: charset: UTF-8 enabled: true force: true###Registration Center eureka: client: serviceUrl: defaultZone: http://localhost:8100/eureka/ server: port: 80 ###Gateway name spring: application: name: service-zuul ##Handle Chinese garbled http: encoding: charset: UTF-8 enabled: true force: true ### Configure Gateway Reverse Proxy zuul: routes: ###Name your

... Hunter
schedule 2 min read
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