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Recently, when spring data jpa is used to maintain many to many relationships between tables, a strange problem arises. When a new object is put into the entity class to maintain many to many relationship set, and then saved with jpa, the following exception will appear. org.springframework.dao.InvalidDataAccessApiUsageException: detached enti ...

1, Profile There are a lot of jar packages involved. Here I choose to help me manage jars by maven <?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. ...

I've uploaded a two-way, one-to-one instance to GitHub, the entrance project, and downloaded and run if you're interested, here are two running problems. Question 1: I left a question at the end of my last blog post.One-to-one Association query comment @OneToOne instance details Problem point: At the en ...

The article refers to: https://blog.csdn.net/long476964/article/details/79677526   . This article introduces the use of the Example class. Spring datajpa official document: https://docs.spring.io/spring-data/jpa/docs/2.0.9.RELEASE/reference/html/#query-by-example (English tycoon moves here) spring data jpa Example condi ...

I. Preface When we design tables for projects, sometimes we need to use composite primary keys to identify uniqueness. If the project's persistence layer adopts hibernate framework, we can use @ EmbeddedId annotation to achieve this requirement. 2, Table design CREATE TABLE `mkt_mas_cpcus` ( `CR_ORG_NBR` decimal(3,0) NO ...

Here, we take Maven as an example to send the map first, then the text information of Maven and configuration file (easy to copy and paste); the Oracle11g database jar package is in the lib directory of Oracle database installation, which is not specifically introduced here Spring integrates Jpa configuration files: be careful, ...

Service registration and discovery, service discovery is mainly used to achieve automatic registration and discovery of individual micro-service instances. It is the core of micro-service governance. To learn Spring Cloud Alibaba, first of all, you need to understand the service registration and discovery component in the framework, Nacos. 1. S ...

Basic concepts Concurrency and Parallelism Concurrency: Two or more events occur at the same time interval.When multiple threads are operating, if the system has only one CPU, it is impossible for the system to actually run more than one thread at the same time. It can only divide the CPU run time into several time periods, then assign time pe ...

First of all, look at a business requirement: fuzzy query data by book name and paging function. Usually, you can write the query method as follows, but it is troublesome if there are many query dimensions. A new BaseDao is written to deal with this problem. The BaseDao code is as follows: package com.zking.eight.util; import j ...

Environment: oracle11g, MyEclipse 2014 First, add the spring framework to the web project             Now that you've added the spring framework     Then we start to add the Hibernate Framework                           At this point, the Hibernate framework is added applicationContext.xml configuration file <?xml version="1.0" encod ...