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introduce The concept of idempotency is that the impact of any multiple executions is the same as that of one execution. According to this meaning, the final explanation is that the impact on the database can only be one-time and cannot be processed repeatedly. The means are as follows Create a unique index of the database token mechanism ...

Advance preparation For the smooth development of the story, we first create a table and insert some records into the table. The following is the SQL statement: CREATE TABLE hero ( number INT, name VARCHAR(100), country varchar(100), PRIMARY KEY (number), KEY idx_name (name) ) Engine=InnoDB CHARSET=utf8; INSERT INTO hero ...

Special invited author of enjoying learning class: Dream chasing youth Reprint, please state the source! ###Foreword When we do development, we always emphasize the concept of data type. In Java, it is divided into basic type and reference data type. There are eight basic data types. In addition to classes, we can also use the way of interfa ...

Design mode summary significance The essence of design pattern is the practical application of object-oriented design principles. It is a full understanding of the encapsulation, inheritance and polymorphism of classes, as well as the association and composition of classes Basic elements name Question: the application environment of th ...

##Foreword I wrote a paragraph of logic in Java 8, but my colleagues said they couldn't understand it. The following is the business background. You can have a look together! Business background First of all, the business needs are as follows: pull all orders from the third-party e-commerce platform and save them to the company's own database ...

In this article, we mainly share a practical case: unknown bytecode instruction. Next, we will take a look at the application of bytecode by introducing some common features in the Java language. Because there are many Java features, here we will only introduce some features we often encounter. javap is a sharp weapon in your hand. Complex con ...

1, Background of the incident One day last month, due to the lack of cluster space, an employee with higher authority in the company executed the manual cleaning command on an online cluster through the springboard machine and frantically executed hadoop fs -rmr -skipTrash /user/hive/warehouse/xxxxx. Suddenly, I didn't know whether it was the ...

Cluster is a kind of computer system, which is connected by a group of loosely integrated computer software and / or hardware to complete the computing work with high close cooperation. In a sense, they can be regarded as a computer. A single computer in a cluster system is usually called a node and is usually connected through a local area net ...

Original: enjoy learning classroom lecturer Reprint, please state the source! For example, frameworks that handle large amounts of information, such as Spring batch processing, use threads to manage data. Operating threads or CPU processes at the same time can improve performance, resulting in faster and more efficient programs. W ...

Recommended reading: This set of 40K+star learning notes on Github can help you handle more than 95% of Java interviews It's no exaggeration to say that this SpringBoot study guide can solve 98% of the problems you encounter Give me a break; orz! This set of PDF of SQL becoming God, which is expected by thousands of people, is finally open ...