Java 如何解决SQL完整性约束违规异常
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how to Solve SQL Integrity Constraint Violation Exception
提问by mussdroid
I created an entity class that has the same properties as project.java, and created a class where I can persist the entity object. Also, I created a database using databases in Netbeans using embedded JDBC. I have the persistence.xml, which provides the properties to connect the db, and is used the persitence class on entitymanagerfactoryobject. The connection seems fine but I am having Internal Exception: java.sql.SQLIntegrityConstraintViolationException: Column 'PROJECT_ID' cannot accept a NULL value.error.
我创建了一个与 project.java 具有相同属性的实体类，并创建了一个可以持久化实体对象的类。此外，我使用嵌入式JDBC. 我有persistence.xml，它提供连接数据库的属性，并在entitymanagerfactory对象上使用持久性类。连接看起来很好，但我遇到了Internal Exception: java.sql.SQLIntegrityConstraintViolationException: Column 'PROJECT_ID' cannot accept a NULL value.错误。
Is it ok to create the db manually (executing the ddl) or should I create the table in the persistence.xmlusing property name="javax.persistence.jdbc.url"" value="create-tables?
可以手动创建数据库（执行 ddl）还是应该在persistence.xmlusing 中创建表property name="javax.persistence.jdbc.url"" value="create-tables？
Regards
问候
回答by mursch
You have to set the value of the column PROJECT_ID.
您必须设置 column 的值PROJECT_ID。
You can either do this in your code, for example by using the annotations @SequenceGeneratoror @GenericGenerator,
or use db features (trigger) to set the id during insert.
您可以在代码中执行此操作，例如通过使用注释@SequenceGenerator或@GenericGenerator，或使用 db 功能（触发器）在插入期间设置 id。
