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Common hadoop cluster namenode(nn) secondarynamenode(2nn) datanode(dn) The problems of common hadoop cluster Is there a single point of failure with datanode? No, because datanode has multiple machines and a copy mechanism as guarantee Is there a single point of failure with the namenode? Yes, because 2nn can't replac ...

This article has been exclusively authorized to be used by [Xinhua front and back development]. Use other platforms after contacting the author [TOC] brief introduction JDBC, Hibernate and Mybatis are the most commonly used databases. By connecting to the database through JDBC, we will find that the workload is quite complex. We have to deal wi ...

Analysis of multi part types in spring MVC On the modify goods page, add the upload goods picture function. When submitting the data of enctype = "multipart / form data" in the page form, spring MVC needs to parse the data of multipart type. Configure the multipart type parser in springmvc.xml. <!-- File upload --> <bean id=" ...

In developing SQL Server word order, it may be necessary to convert all values of a column in the table to comma separated strings for presentation. for instance:   IF OBJECT_ID('tempdb..#tempTable') IS NOT NULL BEGIN DROP TABLE #tempTable END CREATE TABLE #tempTable ([ID] INT NOT NULL,[Category] NVARCHAR(40) NULL) INSERT INTO ...

Advanced parameter binding 1. Parameter binding of array type Complete parameter transfer based on bulk deletion @RequestMapping("queryItem") public String queryItem(QueryVo vo, Integer[] ids) { System.out.println(vo); //Output the array passed in if (ids != null && ids.length > 0) { for (Integer id : id ...

In the target detection task, input the coordinates of a picture and target box. After the annotation tool is completed, the coordinates are usually saved in the xml file. When we need to modify the annotation data according to our own business needs, it is more appropriate to modify the xml file directly because of the high co ...

1. Background After the new Spring Boot is built, it will bring its own packaging method. Now it is usually packaged into jar package. Of course, you can also pack it into war package, I won't introduce it! This article mainly wants to talk about the self-contained packaging method and assembly packaging method. What are the differences, advant ...

The dao, service and controller of the system are all thrown upward through throws Exception, and finally the spring MVC front-end controller is handed over to the exception processor for processing. Spring MVC provides a global exception handler (only one exception handler in a system) for unified exception handling. Custom exception class Def ...

Catalog 1. What is MyBatis? 2. Integration Mode 3. Actual Warfare IV. Testing This article describes how SpringBoot integrates Mybatis (XML configuration). 1. What is MyBatis? MyBatis is an excellent persistence layer framework that supports customization of SQL, stored procedures, and adv ...

Annotation configuration Statement bean @Component component @Service business logic layer use @Repository data access layer (dao) use @Controller presentation layer use Injecting bean @Autowired Write function bean Where @ Component, @ Service, @ Repository and @ Controller are the same, you can choose package com.example.dem ...