异常产生场景及异常信息
上周,由于在Mybatis的Mapper接口方法中使用实现了Map.Entry接口的泛型类,同时此方法对应的sql语句也使用了foreach标签,导致出现了异常。如下为异常信息:
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org.apache.ibatis.exceptions.PersistenceException: ### Error updating database. Cause: org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'key' in 'class java.lang.Integer' ### The error may involve org.guojing.test.spring.server.GoodsRoomnight30daysMapper.insertBatch-Inline ### The error occurred while setting parameters ### SQL: REPLACE INTO goods_roomnight_30days (goods_id, checkin_room_night_30days) VALUES (?, ?) , (?, ?), (?, ?), (?, ?) ### Cause: org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'key' in 'class java.lang.Integer' at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java: 30 ) at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java: 200 ) at org.apache.ibatis.session.defaults.DefaultSqlSession.insert(DefaultSqlSession.java: 185 ) at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java: 57 ) at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java: 53 ) at com.sun.proxy.$Proxy4.insertBatch(Unknown Source) at org.guojing.test.spring.server.GoodsRoomnight30daysTest.test(GoodsRoomnight30daysTest.java: 47 ) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java: 57 ) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java: 43 ) at java.lang.reflect.Method.invoke(Method.java: 606 ) at org.junit.runners.model.FrameworkMethod$ 1 .runReflectiveCall(FrameworkMethod.java: 47 ) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java: 12 ) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java: 44 ) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java: 17 ) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java: 26 ) at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java: 27 ) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java: 271 ) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java: 70 ) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java: 50 ) at org.junit.runners.ParentRunner$ 3 .run(ParentRunner.java: 238 ) at org.junit.runners.ParentRunner$ 1 .schedule(ParentRunner.java: 63 ) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java: 236 ) at org.junit.runners.ParentRunner.access$ 000 (ParentRunner.java: 53 ) at org.junit.runners.ParentRunner$ 2 .evaluate(ParentRunner.java: 229 ) at org.junit.runners.ParentRunner.run(ParentRunner.java: 309 ) at org.junit.runner.JUnitCore.run(JUnitCore.java: 160 ) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java: 68 ) at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java: 51 ) at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java: 237 ) at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java: 70 ) Caused by: org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'key' in 'class java.lang.Integer' at org.apache.ibatis.reflection.Reflector.getGetInvoker(Reflector.java: 409 ) at org.apache.ibatis.reflection.MetaClass.getGetInvoker(MetaClass.java: 164 ) at org.apache.ibatis.reflection.wrapper.BeanWrapper.getBeanProperty(BeanWrapper.java: 162 ) at org.apache.ibatis.reflection.wrapper.BeanWrapper.get(BeanWrapper.java: 49 ) at org.apache.ibatis.reflection.MetaObject.getValue(MetaObject.java: 122 ) at org.apache.ibatis.reflection.MetaObject.getValue(MetaObject.java: 119 ) at org.apache.ibatis.mapping.BoundSql.getAdditionalParameter(BoundSql.java: 75 ) at org.apache.ibatis.scripting.defaults.DefaultParameterHandler.setParameters(DefaultParameterHandler.java: 72 ) at org.apache.ibatis.executor.statement.PreparedStatementHandler.parameterize(PreparedStatementHandler.java: 93 ) at org.apache.ibatis.executor.statement.RoutingStatementHandler.parameterize(RoutingStatementHandler.java: 64 ) at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java: 86 ) at org.apache.ibatis.executor.SimpleExecutor.doUpdate(SimpleExecutor.java: 49 ) at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java: 117 ) at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java: 198 ) ... 29 more |
由于本人对Mybatis还不是非常的了解,导致用了很长的时间去debug找具体的异常原因。
接下来介绍我将重现异常并分析导致异常的原因。
异常重现
为了重现上面的异常,写了demo。相关代码如下:
数据库表结构:
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CREATE TABLE `goods_roomnight_30days` ( `goods_id` bigint( 20 ) NOT NULL, `checkin_room_night_30days` int ( 11 ) NOT NULL DEFAULT '0' COMMENT '近30天消费间夜' , PRIMARY KEY (`goods_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT= 'goods的近30天消费间夜' |
KeyValue.java 参数类:
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public class KeyValue<K, V> implements Map.Entry<K, V> { private K key; private V value; public KeyValue() { } public KeyValue(K key, V value) { this .key = key; this .value = value; } @Override public K getKey() { return key; } @Override public V getValue() { return value; } @Override public V setValue(V value) { V oldValue = this .value; this .value = value; return oldValue; } public JSONObject toJSONObject() { return ReportJSONObject.newObject().append(String.valueOf(key), value); } @Override public String toString() { return toJSONObject().toJSONString(); } } |
DAO类GoodsRoomnight30daysMapper.java
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public interface GoodsRoomnight30daysMapper { int deleteByExample(GoodsRoomnight30daysExample example); List<GoodsRoomnight30days> selectByExample(GoodsRoomnight30daysExample example); <K, V> int insertBatch(List<KeyValue<K, V>> records); } |
mybatis-config.xml文件:
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<?xml version= "1.0" encoding= "UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd" > <configuration> <settings> <setting name= "cacheEnabled" value= "false" /> </settings> <!-- 和spring整合后 environments配置将废除,交给spring管理--> <environments default = "development" > <environment id= "development" > <!-- 使用jdbc事务管理--> <transactionManager type= "JDBC" /> <!-- 数据库连接池,整合后一般使用第三方的连接池--> <dataSource type= "POOLED" > <property name= "driver" value= "com.mysql.jdbc.Driver" /> <property name= "url" value= "jdbc:mysql://localhost:3306/hotel_report?characterEncoding=utf-8" /> <property name= "username" value= "test_user" /> <property name= "password" value= "user123" /> </dataSource> </environment> </environments> <mappers> <mapper resource= "mybatis/GoodsRoomnight30daysMapper.xml" /> </mappers> </configuration> |
GoodsRoomnight30daysMapper.xml文件的主要内容:
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<insert id= "insertBatch" parameterType= "list" > REPLACE INTO goods_roomnight_30days (goods_id, checkin_room_night_30days) VALUES <foreach collection= "list" index= "index" item= "item" separator= "," > (#{item.key}, #{item.value}) <!--<choose>--> <!--<when test= "item.value == null" >(#{item.key}, 0 )</when>--> <!--<when test= "item.value != null" >(#{item.key}, #{item.value})</when>--> <!--</choose>--> </foreach> </insert> |
以上为重现此异常的主要代码,完整代码可在Github查看:https://github.com/misterzhou/java-demo/tree/master/test-spring/spring-server
重现异常的测试代码 GoodsRoomnight30daysTest.java:
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package org.guojing.test.spring.server; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import org.guojing.spring.commons.KeyValue; import org.junit.After; import org.junit.Before; import org.junit.Test; import java.io.IOException; import java.io.InputStream; import java.util.ArrayList; import java.util.List; /** * Created at: 2016-12-24 * * @author guojing */ public class GoodsRoomnight30daysTest { SqlSessionFactory sqlSessionFactory; SqlSession sqlSession; GoodsRoomnight30daysMapper goodsRoomnight30daysMapper; @Before public void init() throws IOException { String resource = "mybatis/mybatis-config.xml" ; InputStream inputStream = Resources.getResourceAsStream(resource); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); sqlSession = sqlSessionFactory.openSession( true ); goodsRoomnight30daysMapper = sqlSession.getMapper(GoodsRoomnight30daysMapper. class ); } @Test public void test() { List<KeyValue<Long, Integer>> records = new ArrayList<>(); records.add( new KeyValue<Long, Integer>(1725L, 5 )); records.add( new KeyValue<Long, Integer>(1728L, 3 )); records.add( new KeyValue<Long, Integer>(1730L, null )); records.add( new KeyValue<Long, Integer>(1758L, null )); int deleted = goodsRoomnight30daysMapper.deleteByExample( new GoodsRoomnight30daysExample()); System.out.println( "----- deleted row size: " + deleted); int row = goodsRoomnight30daysMapper.insertBatch(records); System.out.println( "----- affected row: " + row); List<GoodsRoomnight30days> result = goodsRoomnight30daysMapper.selectByExample( new GoodsRoomnight30daysExample()); for (GoodsRoomnight30days item : result) { System.out.println(item.toString()); } } @After public void after() { if (sqlSession != null ) { sqlSession.close(); } } } |
卖个关子,大家先不要往下看,想想导致异常的原因(熟练使用foreach标签的同学应该能看出端倪)。
查找异常过程及异常分析
在项目中,由于DAO方法的参数类和返回结果类经常会包含一个键和键对应的值,为了避免重复定义类,我定义了一个实现了Map.Entry接口的KeyValue泛型类,具体请查看上节。
GoodsRoomnight30daysMapper.insertBatch()
方法就使用了此泛型类。在运行之后就抛出了本文开始提到的异常信息。
看到异常信息后,就把重点放到了是不是Mybatis对泛型的支持不够好上。问了下同事(@胜男),同事在自己的机器上试了下,发现没有异常。这就奇怪了。仔细看了下代码,发现不同之处就是我的KeyValue泛型类实现了Map.Entry接口。 此时还不知道mybatis官网对于foreach标签的说明:
可以将任何可迭代对象(如列表、集合等)和任何的字典或者数组对象传递给foreach作为集合参数。当使用可迭代对象或者数组时,index是当前迭代的次数,item的值是本次迭代获取的元素。当使用字典(或者Map.Entry对象的集合)时,index是键,item是值。
接下来就是通过debug看看,异常产生的具体原因。于是就先用实现了Map.Entry接口的KeyValue类的代码进行debug,通过异常日志可以看到异常是在 DefaultSqlSession.java:200 行抛出,那么将断点打到 DefaultSqlSession.java:197行,然后一步步向下执行,当执行到 ForEachSqlNode.java:73行时,终于焕然大悟。先看下debug调用链图:
再看看具体的代码 ForEachSqlNode.java:73(此类就是foreach标签对象的Node类):
此时具体的异常原因就很明显了,此处的 o 对象的所属的类就是KeyValue类,由于KeyValue类实现了Map.Entry接口,所以 o instance Map.Entry 为true,mybatis就把key值赋给了foreach的index属性,而把value值赋给了item属性,此处也就是把值为5的Integer对象赋给了item属性。所以 GoodsRoomnight30daysMapper.xml 中id为 insertBatch 的select标签的item属性对应的对象也就没有 item.key 和 item.value 属性,这就是最终导致异常的原因。
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<insert id= "insertBatch" parameterType= "list" > REPLACE INTO goods_roomnight_30days (goods_id, checkin_room_night_30days) VALUES <foreach collection= "list" index= "index" item= "item" separator= "," > (#{item.key}, #{item.value}) </foreach> </insert> |
以上所述是小编给大家介绍的Mybatis foreach标签使用不当导致异常的原因浅析,希望对大家有所帮助,如果大家有任何疑问请给我留言,小编会及时回复大家的。在此也非常感谢大家对服务器之家网站的支持!
原文链接:https://my.oschina.net/u/553773/blog/813260