Duplicate entry '234' for key 'PRIMARY' Query

java.sql.SQLException: Duplicate entry '234' for key 'PRIMARY' Query: insert into blog (title,content,category_id,createdtime) values (?,?,?,now()) Parameters: [erg re g, <p>fg f g</p>, 2]
at org.apache.commons.dbutils.QueryRunner.rethrow(QueryRunner.java:359)
at org.apache.commons.dbutils.QueryRunner.update(QueryRunner.java:428)
at org.apache.commons.dbutils.QueryRunner.update(QueryRunner.java:484)
at cn.com.jobedu.blog.AddBlogServlet.doPost(AddBlogServlet.java:62)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
at java.lang.Thread.run(Thread.java:619)
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