jpa

问题 Alright, I've looked around to find this answer for about an hour and I can't see it posted. So I bought the Spring Framework Master Class from in28minutes on Udemy. We have started implementing JPA. However, the Spring Boot versions are different( he is using 2.0.3, I am using 2.4.0). Now I know that's the issue. So the task is to simply connect to a h2 database, and interact with the data. Here is the current code setup I am using: JpaDemoApplication.java package com.in28minutes.database

问题 Alright, I've looked around to find this answer for about an hour and I can't see it posted. So I bought the Spring Framework Master Class from in28minutes on Udemy. We have started implementing JPA. However, the Spring Boot versions are different( he is using 2.0.3, I am using 2.4.0). Now I know that's the issue. So the task is to simply connect to a h2 database, and interact with the data. Here is the current code setup I am using: JpaDemoApplication.java package com.in28minutes.database

问题 I want to save some data coming from the request. for that, I created some entity classes. but why I et this exception? Error executing DDL "create table body_datum (body_datum_id integer not null, key varchar(255), value varchar(255), value_type varchar(255), primary key (body_datum_id)) engine=InnoDB" via Here are my properties. spring.datasource.url= jdbc:mysql://localhost:3306/loadtestdb?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC

问题 I want to save some data coming from the request. for that, I created some entity classes. but why I et this exception? Error executing DDL "create table body_datum (body_datum_id integer not null, key varchar(255), value varchar(255), value_type varchar(255), primary key (body_datum_id)) engine=InnoDB" via Here are my properties. spring.datasource.url= jdbc:mysql://localhost:3306/loadtestdb?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC

问题 My question is pretty similar to the following: JPA: How do I add new Items to a List with a OneToMany annotation Why merging is not cascaded on a one to many relationship JPA with JTA: Persist entity and merge cascaded child entities I also had a look in Wikibooks but still not able to fix my problem So, my problem is that I have a Parent class with childs, and when I add a new child and use entityManager.merge(parent) to update the new children are not inserted and I get an error of null

问题 I am currently implementing a REST API web service using the Dropwizard framework together with dropwizard-hibernate respectively JPA/Hibernate (using a PostgreSQL database). I have a method inside a resource which I annotated with @UnitOfWork to get one transaction for the whole request. The resource method calls a method of one of my DAOs which extends AbstractDAO<MyEntity> and is used to communicate retrieval or modification of my entities (of type MyEntity ) with the database. This DAO

问题 JPA Specification is powerful in order to build WHERE clauses. But, it seems to be defined only for SELECT (with findAll method). Is it possible to have the same behavior with DELETE and UPDATE? So that, it would be possible to avoid selecting scope before deleting or updating it. Thx 回答1: You can use CriteriaUpdate and CriteriaDelete. Im building my specification from a RSQL query here but it can be done in a lot of other ways as well (see https://www.programcreek.com/java-api-examples/index

问题 JPA Specification is powerful in order to build WHERE clauses. But, it seems to be defined only for SELECT (with findAll method). Is it possible to have the same behavior with DELETE and UPDATE? So that, it would be possible to avoid selecting scope before deleting or updating it. Thx 回答1: You can use CriteriaUpdate and CriteriaDelete. Im building my specification from a RSQL query here but it can be done in a lot of other ways as well (see https://www.programcreek.com/java-api-examples/index

问题 I have a Maven project where I generate the JPA metamodel using the Hibernate metamodel generator. <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> <parent> <groupId>xxx</groupId> <artifactId>xxx</artifactId> <version>1.0.0-SNAPSHOT</version> </parent> <artifactId>xxx</artifactId> <dependencies>

问题 Suppose I have two entities as: @Entity public class A { @Id private int id; @ManyToOne private B b; //more attributes } @Entity public class B { @Id private int id; } So, the table for A is having a column as b_id as the foreign key. Now, I want to select just the b_id based on some criteria on other fields. How can I do this using criteria query? I tried doing following which throws IllegalArgumentException saying "Unable to locate Attribute with the given name [b_id] on this ManagedType [A