Mybatis（7）- 源码解析（2）读取配置 Configuration-解析 *Mapper.xml

Mybatis（4）- 源码解析（2）读取配置 Configuration-解析 *Mapper.xml

承接上文：https://blog.youkuaiyun.com/sql2008help/article/details/118096277

接着 XMLConfigBuilder parseConfiguration 方法解析 mappers 配置

this.mapperElement(root.evalNode("mappers"));

XMLConfigBuilder mapperElement 方法，循环遍历 <mappers> ，

private void mapperElement(XNode parent) throws Exception {
    if (parent != null) {
        Iterator var2 = parent.getChildren().iterator();

        while(true) {
            while(var2.hasNext()) {
                XNode child = (XNode)var2.next();
                String resource;
                if ("package".equals(child.getName())) {
                    resource = child.getStringAttribute("name");
                    this.configuration.addMappers(resource);
                } else {
                    // 读取 *Mapper.xml 配置 如：mybatis/ActorMapper.xml
                    resource = child.getStringAttribute("resource");
                    String url = child.getStringAttribute("url");
                    String mapperClass = child.getStringAttribute("class");
                    XMLMapperBuilder mapperParser;
                    InputStream inputStream;
                    if (resource != null && url == null && mapperClass == null) {
                        ErrorContext.instance().resource(resource);
                        inputStream = Resources.getResourceAsStream(resource);
                        // 构建 读取 mybatis/ActorMapper.xml 配置的 对象 XMLMapperBuilder
                        mapperParser = new XMLMapperBuilder(inputStream, this.configuration, resource, this.configuration.getSqlFragments());
                        mapperParser.parse();
                    } else if (resource == null && url != null && mapperClass == null) {
                        ErrorContext.instance().resource(url);
                        inputStream = Resources.getUrlAsStream(url);
                        mapperParser = new XMLMapperBuilder(inputStream, this.configuration, url, this.configuration.getSqlFragments());
                        mapperParser.parse();
                    } else {
                        if (resource != null || url != null || mapperClass == null) {
                            throw new BuilderException("A mapper element may only specify a url, resource or class, but not more than one.");
                        }

                        Class<?> mapperInterface = Resources.classForName(mapperClass);
                        // 向 configuration 中 MapperRegistry 属性注册 MapperProxyFactory
                        this.configuration.addMapper(mapperInterface);
                    }
                }
            }

            return;
        }
    }
}

解析 *Mapper.xml

XMLMapperBuilder

public class XMLMapperBuilder extends BaseBuilder {
    private final XPathParser parser;
    private final MapperBuilderAssistant builderAssistant;
    private final Map<String, XNode> sqlFragments;
    private final String resource;
}

XMLMapperBuilder parse 方法

public void parse() {
    if (!this.configuration.isResourceLoaded(this.resource)) {
        // 
        this.configurationElement(this.parser.evalNode("/mapper"));
        this.configuration.addLoadedResource(this.resource);
        this.bindMapperForNamespace();
    }

    this.parsePendingResultMaps();
    this.parsePendingCacheRefs();
    this.parsePendingStatements();
}

XMLMapperBuilder configurationElement 方法

private void configurationElement(XNode context) {
    try {
        String namespace = context.getStringAttribute("namespace");
        if (namespace != null && !namespace.isEmpty()) {
            this.builderAssistant.setCurrentNamespace(namespace);
            this.cacheRefElement(context.evalNode("cache-ref"));
            // 构建二级缓存类
            this.cacheElement(context.evalNode("cache"));
            this.parameterMapElement(context.evalNodes("/mapper/parameterMap"));
            this.resultMapElements(context.evalNodes("/mapper/resultMap"));
            this.sqlElement(context.evalNodes("/mapper/sql"));
            // 解析 select | update | insert SQL语句
            this.buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
        } else {
            throw new BuilderException("Mapper's namespace cannot be empty");
        }
    } catch (Exception var3) {
        throw new BuilderException("Error parsing Mapper XML. The XML location is '" + this.resource + "'. Cause: " + var3, var3);
    }
}

XMLMapperBuilder buildStatementFromContext 方法，循环遍历 ActorMapper.xml 配置文件中 SQL 语句

private void buildStatementFromContext(List<XNode> list, String requiredDatabaseId) {
    Iterator var3 = list.iterator();

    while(var3.hasNext()) {
        XNode context = (XNode)var3.next();
        XMLStatementBuilder statementParser = new XMLStatementBuilder(this.configuration, this.builderAssistant, context, requiredDatabaseId);

        try {
            statementParser.parseStatementNode();
        } catch (IncompleteElementException var7) {
            this.configuration.addIncompleteStatement(statementParser);
        }
    }

}

解析 SQL 语句

XMLMapperBuilder ，*Mapper.xml 中 SQL 语句通过 XMLMapperBuilder 类解析

public class XMLStatementBuilder extends BaseBuilder {
    private final MapperBuilderAssistant builderAssistant;
    private final XNode context;
    private final String requiredDatabaseId;
}

XMLMapperBuilder parseStatementNode

public void parseStatementNode() {
    String id = this.context.getStringAttribute("id");
    String databaseId = this.context.getStringAttribute("databaseId");
    if (this.databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) {
        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());
        String parameterType = this.context.getStringAttribute("parameterType");
        Class<?> parameterTypeClass = this.resolveClass(parameterType);
        String lang = this.context.getStringAttribute("lang");
        LanguageDriver langDriver = this.getLanguageDriver(lang);
        this.processSelectKeyNodes(id, parameterTypeClass, langDriver);
        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;
        }

        SqlSource sqlSource = langDriver.createSqlSource(this.configuration, this.context, parameterTypeClass);
        StatementType statementType = StatementType.valueOf(this.context.getStringAttribute("statementType", StatementType.PREPARED.toString()));
        Integer fetchSize = this.context.getIntAttribute("fetchSize");
        Integer timeout = this.context.getIntAttribute("timeout");
        String parameterMap = this.context.getStringAttribute("parameterMap");
        String resultType = this.context.getStringAttribute("resultType");
        Class<?> resultTypeClass = this.resolveClass(resultType);
        String resultMap = this.context.getStringAttribute("resultMap");
        String resultSetType = this.context.getStringAttribute("resultSetType");
        ResultSetType resultSetTypeEnum = this.resolveResultSetType(resultSetType);
        if (resultSetTypeEnum == null) {
            resultSetTypeEnum = this.configuration.getDefaultResultSetType();
        }

        String keyProperty = this.context.getStringAttribute("keyProperty");
        String keyColumn = this.context.getStringAttribute("keyColumn");
        String resultSets = this.context.getStringAttribute("resultSets");
        // 将解析好的 SQL 语句添加到  configuration 中
        this.builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType, fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass, resultSetTypeEnum, flushCache, useCache, resultOrdered, (KeyGenerator)keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
    }
}

MapperBuilderAssistant addMappedStatement 方法

public MappedStatement addMappedStatement(String id, SqlSource sqlSource, StatementType statementType, SqlCommandType sqlCommandType, Integer fetchSize, Integer timeout, String parameterMap, Class<?> parameterType, String resultMap, Class<?> resultType, ResultSetType resultSetType, boolean flushCache, boolean useCache, boolean resultOrdered, KeyGenerator keyGenerator, String keyProperty, String keyColumn, String databaseId, LanguageDriver lang, String resultSets) {
    if (this.unresolvedCacheRef) {
        throw new IncompleteElementException("Cache-ref not yet resolved");
    } else {
        id = this.applyCurrentNamespace(id, false);
        boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
        org.apache.ibatis.mapping.MappedStatement.Builder statementBuilder = (new org.apache.ibatis.mapping.MappedStatement.Builder(this.configuration, id, sqlSource, sqlCommandType)).resource(this.resource).fetchSize(fetchSize).timeout(timeout).statementType(statementType).keyGenerator(keyGenerator).keyProperty(keyProperty).keyColumn(keyColumn).databaseId(databaseId).lang(lang).resultOrdered(resultOrdered).resultSets(resultSets).resultMaps(this.getStatementResultMaps(resultMap, resultType, id)).resultSetType(resultSetType).flushCacheRequired((Boolean)this.valueOrDefault(flushCache, !isSelect)).useCache((Boolean)this.valueOrDefault(useCache, isSelect)).cache(this.currentCache);
        ParameterMap statementParameterMap = this.getStatementParameterMap(parameterMap, parameterType, id);
        if (statementParameterMap != null) {
            statementBuilder.parameterMap(statementParameterMap);
        }

        MappedStatement statement = statementBuilder.build();
        // 将解析好的 SQL 语句封装称 MappedStatement 对象添加到 configuration 
        // Map<String, MappedStatement> mappedStatements 键值对中
        this.configuration.addMappedStatement(statement);
        return statement;
    }
}