更新MySQL数据库时报错：Duplicate entry '3' for key 1 Query:

Question

[size=large][color=red]Duplicate entry '3' for key 1 Query: update blog set title=?,content=?, id=? Parameters: [第2篇文章,

这是第2篇文章的内容aaaaaaaaaaaaaaaaaaaaa

, 3][/color][/size]
at org.apache.commons.dbutils.QueryRunner.rethrow(QueryRunner.java:540)
at org.apache.commons.dbutils.QueryRunner.update(QueryRunner.java:597)
at org.apache.commons.dbutils.QueryRunner.update(QueryRunner.java:653)
at com.hgl.blog.FinalEditBlogServlet.doPost(FinalEditBlogServlet.java:54)
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(Unknown Source)

这是哪里的错误呢？？？怎么更新数据库不行啊 ？？？那个3是这条记录在文章中的id值。