I have 2 tables, devices which contains a list of devices and dev_tags, which contains a list of asset tags for these devices. The tables join on dev_serial_num, which is the primary key of neither table. The devices are unique on their ip_address field and they have a primary key identified by dev_id. The devices "age out" after 2 weeks. Therefore, the same piece of hardware can show up more than once in devices.

I mention that to explain why there is a OneToMany relationship between dev_tags and devices where it seems that this should be a OneToOne relationship.

So I have my 2 entities

@Entity
@Table(name = "dev_tags")
public class DevTags implements Serializable {

private Integer tagId;
private String devTagId;
private String devSerialNum;
private List<Devices> devices;

@Id
@GeneratedValue
@Column(name = "tag_id")
public Integer getTagId() {
	return tagId;
}

public void setTagId(Integer tagId) {
	this.tagId = tagId;
}

@Column(name="dev_tag_id")
public String getDevTagId() {
	return devTagId;
}

public void setDevTagId(String devTagId) {
	this.devTagId = devTagId;
}

@Column(name="dev_serial_num")
public String getDevSerialNum() {
	return devSerialNum;
}

public void setDevSerialNum(String devSerialNum) {
	this.devSerialNum = devSerialNum;
}


@OneToMany(mappedBy="devSerialNum")
public List<Devices> getDevices() {
	return devices;
}

public void setDevices(List<Devices> devices) {
	this.devices = devices;
}


}

and this one

public class Devices implements java.io.Serializable {

private Integer devId;
private Integer officeId;
private String devSerialNum;
private String devPlatform;
private String devName;
private OfficeView officeView;
private DevTags devTag;

public Devices() {
}

@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "dev_id", unique = true, nullable = false)
public Integer getDevId() {
	return this.devId;
}

public void setDevId(Integer devId) {
	this.devId = devId;
}

@Column(name = "office_id", nullable = false, insertable=false, updatable=false)
public Integer getOfficeId() {
	return this.officeId;
}

public void setOfficeId(Integer officeId) {
	this.officeId = officeId;
}

@Column(name = "dev_serial_num", nullable = false, length = 64, insertable=false, updatable=false)
@NotNull
@Length(max = 64)
public String getDevSerialNum() {
	return this.devSerialNum;
}

public void setDevSerialNum(String devSerialNum) {
	this.devSerialNum = devSerialNum;
}

@Column(name = "dev_platform", nullable = false, length = 64)
@NotNull
@Length(max = 64)
public String getDevPlatform() {
	return this.devPlatform;
}

public void setDevPlatform(String devPlatform) {
	this.devPlatform = devPlatform;
}

@Column(name = "dev_name")
public String getDevName() {
	return devName;
}

public void setDevName(String devName) {
	this.devName = devName;
}

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "office_id")
public OfficeView getOfficeView() {
	return officeView;
}

public void setOfficeView(OfficeView officeView) {
	this.officeView = officeView;
}

@ManyToOne()
@JoinColumn(name="dev_serial_num")
public DevTags getDevTag() {
	return devTag;
}

public void setDevTag(DevTags devTag) {
	this.devTag = devTag;
}

}

I messed around a lot with @JoinColumn(name=) and the mappedBy attribute of @OneToMany and I just cannot get this right. I finally got the darn thing to compile, but the query is still trying to join devices.dev_serial_num to dev_tags.tag_id, the @Id for this entity. Here is the transcript from the console:

13:12:16,970 INFO  [STDOUT] Hibernate: 
select
    devices0_.office_id as office5_2_,
    devices0_.dev_id as dev1_2_,
    devices0_.dev_id as dev1_156_1_,
    devices0_.dev_name as dev2_156_1_,
    devices0_.dev_platform as dev3_156_1_,
    devices0_.dev_serial_num as dev4_156_1_,
    devices0_.office_id as office5_156_1_,
    devtags1_.tag_id as tag1_157_0_,
    devtags1_.comment as comment157_0_,
    devtags1_.dev_serial_num as dev3_157_0_,
    devtags1_.dev_tag_id as dev4_157_0_ 
from
    ond.devices devices0_ 
left outer join
    ond.dev_tags devtags1_ 
        on devices0_.dev_serial_num=devtags1_.tag_id 
where
    devices0_.office_id=?
13:12:16,970 INFO  [IntegerType] could not read column value from result set: dev4_156_1_; Invalid value for getInt() - 'FDO1129Y2U4'
13:12:16,970 WARN  [JDBCExceptionReporter] SQL Error: 0, SQLState: S1009
13:12:16,970 ERROR [JDBCExceptionReporter] Invalid value for getInt() - 'FDO1129Y2U4'

That value for getInt() 'FD01129Y2U4' is a serial number, definitely not an Int! What am I missing/misunderstanding here? Can I join 2 tables on any fields I want or does at least one have to be a primary key?