java-如果输入值不为null则更新列,否则忽略并保留数据库中列的现有值

2023-08-16 19:03:22

我正在使用JAVA和MySQL更新带有输入参数作为JSON输入的表.问题是我不知道所有参数会是什么
输入中存在和不存在,因此可能会为某些输入获取空值
参数.因此,当我运行更新查询时,数据库中的所有列都存储这些空值.我浏览了网络,并查看了各种堆栈解决方案.我发现这是一个经过测试的解决方案,但不适用于我.我对此并不陌生,因此愿意以其他任何方式实现这一目标：

 String updateQuery = "UPDATE " + USER_TABLE + " SET " + USER_TABLE_FIRST_NAME 
    + "=IFNULL("+ user.getFirstName() + "," + USER_TABLE_FIRST_NAME + ")," 
    + USER_TABLE_LAST_NAME + "='" + user.getLastName() + "'," 
    + USER_TABLE_ABOUT_ME + "='" + user.getAboutMe() + "',"
    + USER_TABLE_CITY + "='" + user.getCity() + "',"
    + USER_TABLE_DOB + "='" + user.getDateOfBirth() 
    + "' WHERE " + USER_TABLE_ID + "='" + user.getUserId() + "'";

尽管IFNULL避免设置空值并保留数据库的现有值,但是当它不具有空值时,它无法正常工作
值,但实际值.我只是测试一列,即USER_TABLE_FIRST_NAME.而“用户”是我将输入发送为的JSON对象

    {
     "firstName":"Rakesh",
     "city":"Jaipur"
    }

它给了我下面的错误：

 com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'Rakesh' in 'field list'
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
at com.mysql.jdbc.Util.getInstance(Util.java:381)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1030)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3491)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3423)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1936)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2060)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2536)
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1564)
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1485)
at com.sports.jogar.services.UserService.updateUser(UserService.java:174)
at com.sports.jogar.resources.UserResource.updateUser(UserResource.java:72)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory$1.invoke(ResourceMethodInvocationHandlerFactory.java:81)
at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher$1.run(AbstractJavaResourceMethodDispatcher.java:151)
at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.invoke(AbstractJavaResourceMethodDispatcher.java:171)
at org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$TypeOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:195)
at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:104)
at org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:387)
at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:331)
at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:103)
at org.glassfish.jersey.server.ServerRuntime$1.run(ServerRuntime.java:269)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:297)
at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:252)
at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1025)
at org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:372)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:382)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:345)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:220)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:617)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1527)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1484)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)

解决方法:

您将用户名直接插入SQL中,而没有转义,甚至不加引号.我认为您只是错过了撇号.

为防止SQL注入问题,切勿从动态数据中插入SQL字符串常量,始终使用PreparedStatement并插入标记.

或者,转义值,但使用标记更加安全,并通过允许数据库缓存已编译的SQL语句来提高SQL性能.

String updateQuery = "UPDATE " + USER_TABLE +
                       " SET " + USER_TABLE_FIRST_NAME + "=IFNULL(? ," + USER_TABLE_FIRST_NAME + ")," +
                                 USER_TABLE_LAST_NAME + "=?," +
                                 USER_TABLE_ABOUT_ME + "=?," +
                                 USER_TABLE_CITY + "=?," +
                                 USER_TABLE_DOB + "=?" +
                     " WHERE " + USER_TABLE_ID + "=?";
PreparedStatement stmt = conn.prepareStatement(updateQuery);
stmt.setString(1, user.getFirstName());
stmt.setString(2, user.getLastName());
stmt.setString(3, user.getAboutMe());
stmt.setString(4, user.getCity());
stmt.setString(5, user.getDateOfBirth());
stmt.setString(6, user.getUserId());

注意：答案已扩展至涵盖空检查问题.

当您使用简单的字符串注入时,对于非空值,“ A =’”名称“’”将变为A =’Joe’,对于空值,则为A =’null’,这绝对不是您想要的.

通过使用参数标记,？的值可以为null,这意味着IFNULL(?, Name)将给出所需的确切行为,即使用？的值当它不为null时,以及NAME的值何时？一片空白.

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