com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry

com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry 'gunny111111' for key 'user.userId_UNIQUE'
	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
	at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:403)
	at com.mysql.jdbc.Util.getInstance(Util.java:386)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:936)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3933)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3869)
	at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2524)
	at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2675)
	at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2465)
	at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1915)
	at com.mysql.jdbc.PreparedStatement.executeUpdateInternal(PreparedStatement.java:2136)
	at com.mysql.jdbc.PreparedStatement.executeUpdateInternal(PreparedStatement.java:2070)
	at com.mysql.jdbc.PreparedStatement.executeLargeUpdate(PreparedStatement.java:5187)
	at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2055)
	at user.UserDAO.join(UserDAO.java:34)
	at org.apache.jsp.user.userRegisterAction_jsp._jspService(userRegisterAction_jsp.java:187)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:880)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1601)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.base/java.lang.Thread.run(Thread.java:832)

 

Duplicate entry 'gunny111111' for key 'user.userId_UNIQUE'

 

회원가입 로직 수행 중

해당 에러가 발생하였다.

 

회원가입시 아이디 중복을 방지하기 위해

mysql에서 아이디에 해당하는 컬럼에 unique 제약 조건을 설정하였다.

 

그래서 회원가입시 아이디가 중복 되지 않게 값을 입력 했는데도

해당 에러가 발생하였다.

 

 

원인은.. 

pstmt.executeUpdate() 문의 결과 값을 알고 싶어

console 창에 입력했는데,

 

그것 또한 실행 되어

 

콘솔에서 한 번

 

return 값에서 한 번  총 2번 실행 되기 때문에

 

아이디가 중복 된것으로 나온다..

 

어쩐지..

mysql DB를 확인해보니 값은 들어가 있는데 

UI에서 작동하지 않았던 것이다..

 

 

혹시나 해서 제약조건에 unique 설정을 제거 해보니

 

DB에 데이터가 2개나 들어가 있는 것을 볼 수 있었다.