解决JdbcTemplate查询时报错Incorrect column count: expected 1, actual 17问题
<div id="navCategory"><h5 class="catalogue">目录</h5><ul class="first_class_ul"><li>一、报错内容</li><ul class="second_class_ul"><li>报错背景</li><li>项目代码</li><li>报错信息</li><li>报错原因</li></ul><li>二、解决方法</li><ul class="second_class_ul"></ul><li>三、总结</li><ul class="second_class_ul"></ul></ul></div><p class="maodian"></p><h2>一、报错内容</h2><p class="maodian"></p><h3>报错背景</h3>
<p>使用JdbcTemplate执行查询时，报错了，代码及报错内容如下：</p>
<p class="maodian"></p><h3>项目代码</h3>
<div class="jb51code"><pre class="brush:java;">String sql = "select * from user";
List<User> userList = jdbcTemplate.queryForList(sql,User.class);
</pre></div>
<p class="maodian"></p><h3>报错信息</h3>
<blockquote><p>org.springframework.jdbc.IncorrectResultSetColumnCountException: Incorrect column count: expected 1, actual 5<br /> at org.springframework.jdbc.core.SingleColumnRowMapper.mapRow(SingleColumnRowMapper.java:92)<br /> at org.springframework.jdbc.core.RowMapperResultSetExtractor.extractData(RowMapperResultSetExtractor.java:93)<br /> at org.springframework.jdbc.core.RowMapperResultSetExtractor.extractData(RowMapperResultSetExtractor.java:60)<br /> at org.springframework.jdbc.core.JdbcTemplate$1QueryStatementCallback.doInStatement(JdbcTemplate.java:465)<br /> at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:407)<br /> at org.springframework.jdbc.core.JdbcTemplate.query(JdbcTemplate.java:477)<br /> at org.springframework.jdbc.core.JdbcTemplate.query(JdbcTemplate.java:487)<br /> at org.springframework.jdbc.core.JdbcTemplate.queryForObject(JdbcTemplate.java:497)<br /> at org.springframework.jdbc.core.JdbcTemplate.queryForObject(JdbcTemplate.java:503)<br /> at spring.mybatis.test.MyTest.test01(MyTest.java:25)<br /> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)<br /> at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)<br /> at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)<br /> at java.lang.reflect.Method.invoke(Unknown Source)<br /> at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)<br /> at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)<br /> at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)<br /> at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)<br /> at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)<br /> at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)<br /> at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)<br /> at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)<br /> at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)<br /> at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)<br /> at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)<br /> at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)<br /> at org.junit.runners.ParentRunner.run(ParentRunner.java:363)<br /> at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)<br /> at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)<br /> at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)<br /> at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)<br /> at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)<br /> at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)</p></blockquote>
<p class="maodian"></p><h3>报错原因</h3>
<p>queryForList一般返回的是<code>List<Map<>></code>类型，而不能直接转换成对象。</p>
<div class="jb51code"><pre class="brush:java;">List<Map<String, Object>> list = jdbcTemplate.queryForList("select * from user");
</pre></div>
<p class="maodian"></p><h2>二、解决方法</h2>
<p>将代码修改为以下内容即可：</p>
<div class="jb51code"><pre class="brush:java;">String sql = "select * from user";
List<User> userList = jdbcTemplate.query(sql,new BeanPropertyRowMapper<>(User.class));
</pre></div>
<p class="maodian"></p><h2>三、总结</h2>
<p>以上为个人经验，希望能给大家一个参考，也希望大家多多支持琼殿技术社区。</p>
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