mybatis错误之Could not find result map java.util.List

1.复现错误

报错提示:

13:41:33.539 ERROR com.fast.framework.advice.FastBootControllerAdvice 58 errorHandler - Could not find result map java.util.List org.apache.ibatis.builder.IncompleteElementException: Could not find result map java.util.List
	at org.apache.ibatis.builder.MapperBuilderAssistant.getStatementResultMaps(MapperBuilderAssistant.java:346) ~[mybatis-3.5.0.jar:3.5.0]
	at org.apache.ibatis.builder.MapperBuilderAssistant.addMappedStatement(MapperBuilderAssistant.java:290) ~[mybatis-3.5.0.jar:3.5.0]
	at org.apache.ibatis.builder.xml.XMLStatementBuilder.parseStatementNode(XMLStatementBuilder.java:109) ~[mybatis-3.5.0.jar:3.5.0]
	at org.apache.ibatis.session.Configuration.lambda$buildAllStatements$2(Configuration.java:787) ~[mybatis-3.5.0.jar:3.5.0]
	at java.util.Collection.removeIf(Collection.java:414) ~[?:1.8.0_112]
	at org.apache.ibatis.session.Configuration.buildAllStatements(Configuration.java:786) ~[mybatis-3.5.0.jar:3.5.0]
	at org.apache.ibatis.session.Configuration.hasStatement(Configuration.java:763) ~[mybatis-3.5.0.jar:3.5.0]
	at org.apache.ibatis.session.Configuration.hasStatement(Configuration.java:758) ~[mybatis-3.5.0.jar:3.5.0]
	at com.baomidou.mybatisplus.core.override.MybatisMapperMethod$SqlCommand.resolveMappedStatement(MybatisMapperMethod.java:264) ~[mybatis-plus-core-3.1.0

2.背景

首先去官网确认一下resultMap和resultType的用法自己用对了,本文不讨论基本用法,所以针对已经熟练运用myabtis后的错误

官网:http://www.mybatis.org/mybatis-3/zh/sqlmap-xml.html#select

3.复现场景

(1)Dao层有两个方法,记住这两个fast是正常的,test是错误的

int selectFast();

int selectTest();

(2)对应xml,其中selectTest是有问题的, resultMap="java.util.List" 这样写是错误的



(3)然后我只调用正常的那个方法int selectFast();

masterDao.selectFast()

(4)正常的maven   clean,install,package都正常

(5)编译完启动,也正常启动

(6)然后在通过controller调用正常的方法selectFast的时候报最开始那个错了

Could not find result map java.util.List

(7)类似这个错误会有个提示错误发生的位置,这个错误的提示是:

at com.fast.web.controller.TestController.getString(TestController.java:25) ~[classes/:?]

就是这个TestController的25行,我也是调用的这个方法,按理说都正确

(8)但是不正确的问题是哪里?

我当前调用的这个方法int selectFast();是正常的啊,代码没有问题,并且调用的接口也只是这个方法,所以代码应该正常执行啊。

但是mybatis返回错误了,返回了一个与当时接口调用,不相干的一个方法(int selectTest();)的错误,然而这个错误,在编译阶段,启动阶段都没有报错。在调用其他方法的时候,提示了这个方法的错误,并且提示的有错误的位置是正确方法的位置。

思路:先解决问题再搞清问题,直接把不相干方法的错误改掉,如下修改,int selectTest();方法正常,再次访问提示正常。

当时的解决思路debug:因为我请求的正常方法,返回参数应该是resultType的,但是这个resultMap是哪里来的,并且还报错了,看mybatis提示错误信息位置,

14:04:46.787 ERROR com.fast.framework.advice.FastBootControllerAdvice 58 errorHandler - Could not find result map java.util.List org.apache.ibatis.builder.IncompleteElementException: Could not find result map java.util.List
	at org.apache.ibatis.builder.MapperBuilderAssistant.getStatementResultMaps(MapperBuilderAssistant.java:346) ~[mybatis-3.5.0.jar:3.5.0]
	at org.apache.ibatis.builder.MapperBuilderAssistant.addMappedStatement(MapperBuilderAssistant.java:290) ~[mybatis-3.5.0.jar:3.5.0]
	at org.apache.ibatis.builder.xml.XMLStatementBuilder.parseStatementNode(XMLStatementBuilder.java:109) ~[mybatis-3.5.0.jar:3.5.0]
	at org.apache.ibatis.session.Configuration.lambda$buildAllStatements$2(Configuration.java:787) ~[mybatis-3.5.0.jar:3.5.0]
	at java.util.Collection.removeIf(Collection.java:414) ~[?:1.8.0_112]

找到这个(XMLStatementBuilder.java:109)打个断点,下面是mybatis源码,断点位置放在最后一行。

重新请求,看发过来的resultMap参数

 public void parseStatementNode() {
        String id = this.context.getStringAttribute("id");
        String databaseId = this.context.getStringAttribute("databaseId");
        if (this.databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) {
            Integer fetchSize = this.context.getIntAttribute("fetchSize");
            Integer timeout = this.context.getIntAttribute("timeout");
            String parameterMap = this.context.getStringAttribute("parameterMap");
            String parameterType = this.context.getStringAttribute("parameterType");
            Class parameterTypeClass = this.resolveClass(parameterType);
            String resultMap = this.context.getStringAttribute("resultMap");
            String resultType = this.context.getStringAttribute("resultType");
            String lang = this.context.getStringAttribute("lang");
            LanguageDriver langDriver = this.getLanguageDriver(lang);
            Class resultTypeClass = this.resolveClass(resultType);
            String resultSetType = this.context.getStringAttribute("resultSetType");
            StatementType statementType = StatementType.valueOf(this.context.getStringAttribute("statementType", StatementType.PREPARED.toString()));
            ResultSetType resultSetTypeEnum = this.resolveResultSetType(resultSetType);
            String nodeName = this.context.getNode().getNodeName();
            SqlCommandType sqlCommandType = SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH));
            boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
            boolean flushCache = this.context.getBooleanAttribute("flushCache", !isSelect);
            boolean useCache = this.context.getBooleanAttribute("useCache", isSelect);
            boolean resultOrdered = this.context.getBooleanAttribute("resultOrdered", false);
            XMLIncludeTransformer includeParser = new XMLIncludeTransformer(this.configuration, this.builderAssistant);
            includeParser.applyIncludes(this.context.getNode());
            this.processSelectKeyNodes(id, parameterTypeClass, langDriver);
            SqlSource sqlSource = langDriver.createSqlSource(this.configuration, this.context, parameterTypeClass);
            String resultSets = this.context.getStringAttribute("resultSets");
            String keyProperty = this.context.getStringAttribute("keyProperty");
            String keyColumn = this.context.getStringAttribute("keyColumn");
            String keyStatementId = id + "!selectKey";
            keyStatementId = this.builderAssistant.applyCurrentNamespace(keyStatementId, true);
            Object keyGenerator;
            if (this.configuration.hasKeyGenerator(keyStatementId)) {
                keyGenerator = this.configuration.getKeyGenerator(keyStatementId);
            } else {
                keyGenerator = this.context.getBooleanAttribute("useGeneratedKeys", this.configuration.isUseGeneratedKeys() && SqlCommandType.INSERT.equals(sqlCommandType)) ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
            }

            this.builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType, fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass, resultSetTypeEnum, flushCache, useCache, resultOrdered, (KeyGenerator)keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
        }
    }

然后查看debug参数,我这个接口请求的是selectFast()的啊,正常的方法,但是现在也校验了selectTest();这个有问题的方法。

resultMap返回java.util.List

mybatis错误之Could not find result map java.util.List_第1张图片

所以全局搜selectTest这个方法,修改返回参数,完成bug修复。

总结:这个bug不是什么比较复杂的bug,也不是什么有意义的bug,但是mybatis编译,启动都不报错,在请求正常接口的时候,报一个不相干方法的错误,这个提示位置是有问题的,就会导致大家排查问题浪费大量时间,先记住会有这个问题吧,以后会避免一个坑。

 

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