今天遇到了一个奇怪的错误，报错如下图所示：
org.springframework.dao.DataIntegrityViolationException: Error attempting to get column 'question_id' from result set. Cause: java.sql.SQLDataException: Unsupported conversion from LONG to java.sql.Timestamp ; Unsupported conversion from LONG to java.sql.Timestamp; nested exception is java.sql.SQLDataException: Unsupported conversion from LONG to java.sql.Timestamp at org.springframework.jdbc.support.SQLExceptionSubclassTranslator.doTranslate(SQLExceptionSubclassTranslator.java:84) at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:72) at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:81) at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:88) at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:440) at com.sun.proxy.$Proxy140.selectList(Unknown Source) at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:223) at com.baomidou.mybatisplus.core.override.MybatisMapperMethod.executeForMany(MybatisMapperMethod.java:177) at com.baomidou.mybatisplus.core.override.MybatisMapperMethod.execute(MybatisMapperMethod.java:78) at com.baomidou.mybatisplus.core.override.MybatisMapperProxy.invoke(MybatisMapperProxy.java:96) at com.sun.proxy.$Proxy153.selectList(Unknown Source) at cn.tedu.straw.portal.test.mapper.TestTeacherQuestionMapper.selectOne(TestTeacherQuestionMapper.java:32) 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:498) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:74) at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:84) at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75) at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86) at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61) at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70) at org.junit.runners.ParentRunner.run(ParentRunner.java:363) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68) at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47) at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242) at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70) Caused by: java.sql.SQLDataException: Unsupported conversion from LONG to java.sql.Timestamp at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:114) at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:89) at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:63) at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:73) at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:96) at com.mysql.cj.jdbc.result.ResultSetImpl.getTimestamp(ResultSetImpl.java:903) at com.mysql.cj.jdbc.result.ResultSetImpl.getTimestamp(ResultSetImpl.java:948) at com.zaxxer.hikari.pool.HikariProxyResultSet.getTimestamp(HikariProxyResultSet.java) 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:498) at org.apache.ibatis.logging.jdbc.ResultSetLogger.invoke(ResultSetLogger.java:69) at com.sun.proxy.$Proxy248.getTimestamp(Unknown Source) at org.apache.ibatis.type.DateTypeHandler.getNullableResult(DateTypeHandler.java:39) at org.apache.ibatis.type.DateTypeHandler.getNullableResult(DateTypeHandler.java:28) at org.apache.ibatis.type.BaseTypeHandler.getResult(BaseTypeHandler.java:81) at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.createUsingConstructor(DefaultResultSetHandler.java:671) at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.createByConstructorSignature(DefaultResultSetHandler.java:654) at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.createResultObject(DefaultResultSetHandler.java:618) at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.createResultObject(DefaultResultSetHandler.java:591) at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.getRowValue(DefaultResultSetHandler.java:397) at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValuesForSimpleResultMap(DefaultResultSetHandler.java:354) at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValues(DefaultResultSetHandler.java:328) at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSet(DefaultResultSetHandler.java:301) at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSets(DefaultResultSetHandler.java:194) at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:65) at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:63) at com.sun.proxy.$Proxy236.query(Unknown Source) at com.baomidou.mybatisplus.core.executor.MybatisSimpleExecutor.doQuery(MybatisSimpleExecutor.java:67) at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:324) at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156) at com.baomidou.mybatisplus.core.executor.MybatisCachingExecutor.query(MybatisCachingExecutor.java:155) at com.github.pagehelper.PageInterceptor.intercept(PageInterceptor.java:143) at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:61) at com.sun.proxy.$Proxy235.query(Unknown Source) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:147) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:426) ... 37 more
实体类：
@Data @EqualsAndHashCode(callSuper = false) @Accessors(chain = true) @TableName("teacher_question") @ApiModel(value="TeacherQuestion对象", description="") public class TeacherQuestion implements Serializable { private static final long serialVersionUID = 1L; @TableId(value = "id", type = IdType.AUTO) private Integer id; @TableField("teacher_id") private Integer teacherId; @TableField("question_id") private Integer questionId; @TableField("createtime") private Date createtime; public TeacherQuestion(Integer teacherId, Integer questionId, Date createtime) { this.teacherId = teacherId; this.questionId = questionId; this.createtime = createtime; } }
mapper类和mapper文件如下：
public interface TeacherQuestionMapper extends BaseMapper<TeacherQuestion> { } <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="cn.tedu.straw.portal.mapper.TeacherQuestionMapper"> <!-- 通用查询映射结果 --> <resultMap id="BaseResultMap" type="cn.tedu.straw.portal.model.TeacherQuestion"> <id column="id" property="id" /> <result column="teacher_id" property="teacherId" /> <result column="question_id" property="questionId" /> <result column="createtime" property="createtime" /> </resultMap> </mapper>
数据库表如下：
测试类如下：
@SpringBootTest(classes = StrawPortalApplication.class) @RunWith(SpringRunner.class) public class TestTeacherQuestionMapper { @Resource private TeacherQuestionMapper teacherQuestionMapper; @Test public void selectOne(){ QueryWrapper queryWrapper=new QueryWrapper(); queryWrapper.eq("teacher_id",4); queryWrapper.eq("question_id",44); List<TeacherQuestion> teacherQuestions = teacherQuestionMapper.selectList(queryWrapper); System.out.println(teacherQuestions); } }
反复测试了好多次，不管什么测试条件都是报Cause: java.sql.SQLDataException: Unsupported conversion from LONG to java.sql.Timestamp错误。
后来才想起来自己在实体类里加了一个带参数的构造方法：
public TeacherQuestion(Integer teacherId, Integer questionId, Date createtime) { this.teacherId = teacherId; this.questionId = questionId; this.createtime = createtime; }
这样就导致该实体类没有无参构造方法了，众所周知，一旦我们手动添加了带参数的构造方法，编译器就不会给我们添加默认的无参构造方法。导致mybatis无法new这个实体类。也就无法做映射。
解决的办法是：给该实体类手动添加一个无参构造方法。
public TeacherQuestion() { }
