Error querying database. Cause: java.lang.NumberFormatException: For input string: "{0=null}"
今天做一个mabatis的练习一直报这个错误，网上百度好久终于看到一个大神给了解释，记录下来。
下面是异常信息：
org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: java.lang.NumberFormatException: For input string: "{0=null}"
### Cause: java.lang.NumberFormatException: For input string: "{0=null}"
at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:73)
at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:364)
at com.sun.proxy.$Proxy9.selectOne(Unknown Source)
at org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:159)
at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:63)
at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:43)
at com.sun.proxy.$Proxy14.getUserCount(Unknown Source)
at cn.smbms.service.user.UserServiceImpl.smbmsGetUserCount(UserServiceImpl.java:41)
at cn.smbms.service.user.UserServiceImpl$$FastClassBySpringCGLIB$$cb494c63.invoke()
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:700)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:96)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:260)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:94)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:91)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:633)
at cn.smbms.service.user.UserServiceImpl$$EnhancerBySpringCGLIB$$35c3e689.smbmsGetUserCount()
at UserTest.testGetUserCount(UserTest.java:81)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: java.lang.NumberFormatException: For input string: "{0=null}"
### Cause: java.lang.NumberFormatException: For input string: "{0=null}"
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:23)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:107)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:98)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:62)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:354)
... 42 more
Caused by: java.lang.NumberFormatException: For input string: "{0=null}"
at sun.misc.FloatingDecimal.readJavaFormatString(Unknown Source)
at java.lang.Double.parseDouble(Unknown Source)
at org.apache.ibatis.ognl.OgnlOps.doubleValue(OgnlOps.java:259)
at org.apache.ibatis.ognl.OgnlOps.compareWithConversion(OgnlOps.java:143)
at org.apache.ibatis.ognl.OgnlOps.isEqual(OgnlOps.java:186)
at org.apache.ibatis.ognl.OgnlOps.equal(OgnlOps.java:578)
at org.apache.ibatis.ognl.ASTNotEq.getValueBody(ASTNotEq.java:51)
at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:170)
at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:210)
at org.apache.ibatis.ognl.ASTAnd.getValueBody(ASTAnd.java:56)
at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:170)
at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:210)
at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:333)
at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:413)
at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:395)
at org.apache.ibatis.scripting.xmltags.OgnlCache.getValue(OgnlCache.java:45)
at org.apache.ibatis.scripting.xmltags.ExpressionEvaluator.evaluateBoolean(ExpressionEvaluator.java:29)
at org.apache.ibatis.scripting.xmltags.IfSqlNode.apply(IfSqlNode.java:30)
at org.apache.ibatis.scripting.xmltags.MixedSqlNode.apply(MixedSqlNode.java:29)
at org.apache.ibatis.scripting.xmltags.TrimSqlNode.apply(TrimSqlNode.java:47)
at org.apache.ibatis.scripting.xmltags.MixedSqlNode.apply(MixedSqlNode.java:29)
at org.apache.ibatis.scripting.xmltags.DynamicSqlSource.getBoundSql(DynamicSqlSource.java:37)
at org.apache.ibatis.mapping.MappedStatement.getBoundSql(MappedStatement.java:265)
at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:79)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:104)
... 49 more
我的mapper文件里的sql语句，其中参数#{userRole}为int类型；
我的test类
@Test
public void testGetUserCount() {
int c=0;
int count=userService.smbmsGetUserCount("",c);
logger.info("用户数量："+count);
}其实我还测试了，不只是0会报异常，输入其他任何数字均报异常，会报{你输入的num=null}的异常，百度了好久，终于看到一个大神给了解释，是因为：
在
改过之后：
运行结果正常，感谢大神！！！
另外我又百度了一下原因
Mybatis中的 #$的区别和作用
#相当于对数据 加上 双引号，$则是事什么就显示什么
如：id = #{id}，如果传入的值是99,那么解析成sql时的值为 id =“99”
如：id = ${id}，如果传入的值是99,那么解析成sql时的值为d = 99
本质上的区别：
将传入的数据都当成一个字符串，会对自动传入的数据加一个双引号。#
方式能够很大程度防止sql注入#
方式一般用于传入数据库对象，例如传入表名$
传入的数据直接显示生成在sql中。$
排序时使用order by 动态参数使用$