JPA entity giving error on implementing Bill of material concept

问题

Trying to implement the Bill of Material concept using JPA entity:-
IDE: Eclipse Helios;
Jars: eclipselink2.4.0 , javax.persistence Entity is as follows:

@Id
@TableGenerator(name = "Config_Key_Incrementor", table = "id_generator", pkColumnName = "gen_name", valueColumnName = "gen_value", pkColumnValue = "conifg_id_gen", allocationSize = 1, initialValue = 1)
@GeneratedValue(strategy = TABLE, generator = "Config_Key_Incrementor")
@Column(name = "config_id")
private int configId;

@Column(name = "config_name")
private String configName;

//bi-directional many-to-one association to Bill_Of_Material
@ManyToOne
@PrimaryKeyJoinColumn(name="config_id")
private Configuration parent;

//bi-directional many-to-one association to Bill_Of_Material
@OneToMany(mappedBy="parent")
private List<Configuration> children = new ArrayList<Configuration>();

public Configuration getParent() {
    return parent;
}

public void setParent(Configuration parent) {
    this.parent = parent;
}



public List<Configuration> getChildren() {
    return children;
}

public void setChildren(List<Configuration> children) {
    this.children = children;
}

public int getConfigId() {
    return configId;
}

public void setConfigId(int configId) {
    this.configId = configId;
}

public String getConfigName() {
    return configName;
}

public void setConfigName(String configName) {
    this.configName = configName;
}

Output:

  CREATE TABLE configuration    
  (    
  config_id integer NOT NULL,  
  config_name character varying(255),    
  CONSTRAINT configuration_pkey PRIMARY KEY (config_id ),  
  CONSTRAINT fk_configuration_config_id FOREIGN KEY (config_id)  
         REFERENCES configuration (config_id) MATCH SIMPLE  
         ON UPDATE NO ACTION ON DELETE NO ACTION  
  )

Error: The table is getting created , but the column parent_config_id is missing and its relation to config_id is also missing.

回答1:

You are using @PrimaryKeyJoinColumn(name="config_id") which indicates that the primary key is also a foreign key to the referenced Configuration parent - so it is its own parent. You want to use @JoinColumn to define the foreign key, or leave it blank to have it use the default.

@ManyToOne
@JoinColumn(name="parent_config_id", referencedColumnName="config_id")
private Configuration parent;

来源：https://stackoverflow.com/questions/17923021/jpa-entity-giving-error-on-implementing-bill-of-material-concept

标签

jpa

orm

jpa-2.0

eclipselink