java - Composite primary key with many to one relation ship does not support mapping error -

i have 3 entities form association relationship having composite primary keys foreign key of other tables. these implementation of these entites:

@entity @table(name = "studentscourses", schema = "gpa") @namedquery(name = "getallstdcrs", query = "select sc studentscourses sc") @idclass(studentcourseid.class) public class studentscourses implements serializable { private static final long serialversionuid = 1l;  @id @column(name="studentid", insertable=false, updatable= false) private int studentid;    @id @column(name="crsid", insertable=false, updatable=false) private int crsid;  @manytoone @joincolumn(name="studentid") student student;  @manytoone @joincolumn(name="crsid") course course;  public studentscourses() {     super(); }  public void setstudentid(int studentid) {     this.studentid = studentid; } public int getstudentid() {     return studentid; } public void setcrsid(int crsid) {     this.crsid = crsid; } public int getcrsid() {     return crsid; }    } 

course entity:

@entity @table(name = "courses", schema = "gpa") @namedquery(name = "getallcourses", query = "select c course c") public class course implements serializable {  private static final long serialversionuid = 1l;  @id @generatedvalue(strategy=generationtype.identity) @column(name="crsid") private int crsid; private string name;  @onetomany(mappedby="course", fetch=fetchtype.lazy) private set<assesment> assesments;  @onetomany(mappedby="course", fetch=fetchtype.lazy) private set<studentscourses> studentcourses;  public course() {     super(); }  public int getcrsid() {     return crsid; }  public void setcrsid(int crsid) {     this.crsid = crsid; }  public string getname() {     return name; }  public void setname(string name) {     this.name = name; }  public void setassesments(set<assesment> assesments) {     this.assesments = assesments; }  public set<assesment> getassesments() {     return assesments; }  public void setstudentcourses(set<studentscourses> studentcourses) {     this.studentcourses = studentcourses; }  public set<studentscourses> getstudentcourses() {     return studentcourses; } } 

student entity:

@entity @table(name = "students", schema = "gpa") @namedquery(name = "getallstudents", query = "select s student s") public class student implements serializable {   private static final long serialversionuid = 1l;  @id @generatedvalue(strategy=generationtype.identity) private int studentid; private string studentname;  @onetomany(mappedby="student", fetch = fetchtype.lazy) private set<assesment> assesments;  @onetomany(mappedby="student", fetch = fetchtype.lazy) private set<studentscourses> studentcourses;  public student() {     super(); }  public int getstudnetid() {     return studentid; }  public void setstudnetid(int stdid) {     this.studentid = stdid; }  public void setstudentname(string studentname) {     this.studentname = studentname; }  public string getstudentname() {     return studentname; }  public void setassesments(set<assesment> assesments) {     this.assesments = assesments; }  public set<assesment> getassesments() {     return assesments; }  public void setstudentcourses(set<studentscourses> studentcourses) {     this.studentcourses = studentcourses; }  public set<studentscourses> getstudentcourses() {     return studentcourses; } } 

when try lanuch program getting following error:

[4/5/13 0:30:15:243 edt] 00000028 webapp        e com.ibm.ws.webcontainer.webapp.webapp logservleterror srve0293e: [servlet error]-[com.gpa.app.servlet.loginservlet]: <openjpa-2.1.1-snapshot-r422266:1141200 fatal user error> org.apache.openjpa.persistence.argumentexception: field "com.gpa.app.entities.course.studentcourses" cannot declare mapped field. mapping strategy (org.apache.openjpa.jdbc.meta.strats.handlerfieldstrategy) not support mapping field. 

what cause of prob. appreciate help.

so problem in @id classes. in class didn't implemented equal , hash code method , didn't implemented serializable. after done worked smoothly. eelke, gave me idea try in different version , helped me find out cause.

my modified code in looks this:

public class studentcourseid implements serializable{  private static final long serialversionuid = 1l; private int studentid; private int crsid;  public studentcourseid() { }  public studentcourseid(int studentid, int crsid) {     this.studentid = studentid;     this.crsid = crsid; }  public void setstudentid(int studentid) {     this.studentid = studentid; }  public int getstudentid() {     return studentid; }  public void setcrsid(int crsid) {     this.crsid = crsid; }  public int getcrsid() {     return crsid; } public int hashcode() {     return studentid + crsid; }  public boolean equals(object o) {     return ((o instanceof studentcourseid)             && studentid == ((studentcourseid) o).getstudentid() && crsid == ((studentcourseid) o)                 .getcrsid()); }     }  public int getcrsid() {     return crsid; }    } 

hope helps in future.

thanks, sas