购物车添加商品

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       购物车每次添加数量为1的时候就报错，但是参数count改成比1大的时候就能添加成功

报错如下：

Caused by: java.sql.SQLIntegrityConstraintViolationException: Duplicate entry '1' for key 'imooc_mall_cart.PRIMARY'

at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:117) ~[mysql-connector-java-8.0.18.jar:8.0.18]

at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) ~[mysql-connector-java-8.0.18.jar:8.0.18]

at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) ~[mysql-connector-java-8.0.18.jar:8.0.18]

at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:953) ~[mysql-connector-java-8.0.18.jar:8.0.18]

at com.mysql.cj.jdbc.ClientPreparedStatement.execute(ClientPreparedStatement.java:370) ~[mysql-connector-java-8.0.18.jar:8.0.18]

at com.zaxxer.hikari.pool.ProxyPreparedStatement.execute(ProxyPreparedStatement.java:44) ~[HikariCP-3.4.1.jar:?]

at com.zaxxer.hikari.pool.HikariProxyPreparedStatement.execute(HikariProxyPreparedStatement.java) ~[HikariCP-3.4.1.jar:?]

at sun.reflect.GeneratedMethodAccessor109.invoke(Unknown Source) ~[?:?]

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_202]

at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_202]

at org.apache.ibatis.logging.jdbc.PreparedStatementLogger.invoke(PreparedStatementLogger.java:59) ~[mybatis-3.4.6.jar:3.4.6]

at com.sun.proxy.$Proxy173.execute(Unknown Source) ~[?:?]

at org.apache.ibatis.executor.statement.PreparedStatementHandler.update(PreparedStatementHandler.java:46) ~[mybatis-3.4.6.jar:3.4.6]

at org.apache.ibatis.executor.statement.RoutingStatementHandler.update(RoutingStatementHandler.java:74) ~[mybatis-3.4.6.jar:3.4.6]

at org.apache.ibatis.executor.SimpleExecutor.doUpdate(SimpleExecutor.java:50) ~[mybatis-3.4.6.jar:3.4.6]

at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:117) ~[mybatis-3.4.6.jar:3.4.6]

at org.apache.ibatis.executor.CachingExecutor.update(CachingExecutor.java:76) ~[mybatis-3.4.6.jar:3.4.6]

at sun.reflect.GeneratedMethodAccessor144.invoke(Unknown Source) ~[?:?]

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_202]

at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_202]

at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:63) ~[mybatis-3.4.6.jar:3.4.6]

at com.sun.proxy.$Proxy171.update(Unknown Source) ~[?:?]

at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:198) ~[mybatis-3.4.6.jar:3.4.6]

at org.apache.ibatis.session.defaults.DefaultSqlSession.insert(DefaultSqlSession.java:185) ~[mybatis-3.4.6.jar:3.4.6]

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_202]

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_202]

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_202]

at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_202]

at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433) ~[mybatis-spring-1.3.2.jar:1.3.2]

... 87 more