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关于JPA 主键,自定义生成遇到的问题,愚蠢的笔记

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第一次报错: ids for this class must be manually assigned before calling save()

在报这个问题的时候,一定去代码中去查看自己代码set设ID的逻辑,ID的值没有被设置

下面是我写的代码,可以看出,在上面setId,可是下面BeanUtils工具引用dto对象将master原值给覆盖了

PS: 以下面说明->org.springframework.beans.BeanUtils工具可以将dto对象对应master对象的字段替换,免去了一堆无聊的setter

Master master = new Master();
Master.setId(id);
Master.setAmount(amount);
BeanUtils.copyProperties(dto, master); //此处是错误的,会覆盖前面的值
repository.save(master);

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补充学习, 关于JPA提供主键生成,@GeneratorValue 4种策略以及支持的数据库

GenerationType.TABLE ---mysql, oracle, postgresql, kingbase...
GenerationType.AUTO ---mysql, oracle, postgresql, kingbase...
GenerationType.IDENTITY ---mysql, postgresql, kingbase...
GenerationType.SEQUENCE ---oracle, postgresql, kingbase...

自定义生成主键,也有策略生成器,@GenericGenerator注解,该注解要配合@GeneratorValue一起使用

@GeneratedValue注解中的generator属性和@GenericGenerator注解中name属性保持一致,strategy属性表示hibernate的主键生成策略

jar : org.hibernate:hibernate-core:5.2.16.Final的DefaultIdentifierGeneratorFactory类中的14种方式

public DefaultIdentifierGeneratorFactory() {
    this.register("uuid2", UUIDGenerator.class);
    this.register("guid", GUIDGenerator.class);
    this.register("uuid", UUIDHexGenerator.class);
    this.register("uuid.hex", UUIDHexGenerator.class);
    this.register("assigned", Assigned.class);
    this.register("identity", IdentityGenerator.class);
    this.register("select", SelectGenerator.class);
    this.register("sequence", SequenceStyleGenerator.class);
    this.register("seqhilo", SequenceHiLoGenerator.class);
    this.register("increment", IncrementGenerator.class);
    this.register("foreign", ForeignGenerator.class);
    this.register("sequence-identity", SequenceIdentityGenerator.class);
    this.register("enhanced-sequence", SequenceStyleGenerator.class);
    this.register("enhanced-table", TableGenerator.class);
}

使用方式: ↓↓↓

@Id
@GeneratedValue(generator = "orderId")
@GenericGenerator(name = "orderId",strategy = "uuid")
private String orderId;

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ids for this class must be manually assigned before calling save()

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