Mybatis源码分析-2 解析mapper文件

接上篇 juejin.cn/post/684490…
本篇主要分析下解析mapper文件的部分。

private void configurationElement(XNode context) {
   try {
   // 熟悉的namespace，，不能为空
     String namespace = context.getStringAttribute("namespace");
     if (namespace == null || namespace.isEmpty()) {
       throw new BuilderException("Mapper's namespace cannot be empty");
     }
     builderAssistant.setCurrentNamespace(namespace);
     // 缓存相关的配置
     cacheRefElement(context.evalNode("cache-ref"));
     cacheElement(context.evalNode("cache"));
     // 1️⃣ 参数映射（已废弃，不推荐使用）  这四块代码又很多。 看吧继续。👇下面代码
     parameterMapElement(context.evalNodes("/mapper/parameterMap"));
     // 2️⃣ 结果映射
     resultMapElements(context.evalNodes("/mapper/resultMap"));
     // 3️⃣ sql语句
     sqlElement(context.evalNodes("/mapper/sql"));
     // 4️⃣ 根据语句类型构建
     buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
   } catch (Exception e) {
     throw new BuilderException("Error parsing Mapper XML. The XML location is '" + resource + "'. Cause: " + e, e);
   }
 }

2️⃣结果映射
private void resultMapElements(List<XNode> list) {
    for (XNode resultMapNode : list) {
      try {
        resultMapElement(resultMapNode);
      } catch (IncompleteElementException e) {
        // ignore, it will be retried
      }
    }
  }

private ResultMap resultMapElement(XNode resultMapNode) {
    return resultMapElement(resultMapNode, Collections.emptyList(), null);
}

private ResultMap resultMapElement(XNode resultMapNode, List<ResultMapping> additionalResultMappings, Class<?> enclosingType) {
    ErrorContext.instance().activity("processing " + resultMapNode.getValueBasedIdentifier());
    // 获取redsultMap的type属性
    String type = resultMapNode.getStringAttribute("type",
        resultMapNode.getStringAttribute("ofType",
            resultMapNode.getStringAttribute("resultType",
                resultMapNode.getStringAttribute("javaType"))));
    // 加载ResultMap的type类到内存
    Class<?> typeClass = resolveClass(type);
    
    if (typeClass == null) {
      typeClass = inheritEnclosingType(resultMapNode, enclosingType);
    }
    Discriminator discriminator = null;
    List<ResultMapping> resultMappings = new ArrayList<>(additionalResultMappings);
    
    // 处理resultMap的子dom
    List<XNode> resultChildren = resultMapNode.getChildren();
    for (XNode resultChild : resultChildren) {
        // 构造器
      if ("constructor".equals(resultChild.getName())) {
        processConstructorElement(resultChild, typeClass, resultMappings);
        //discriminator鉴别器
      } else if ("discriminator".equals(resultChild.getName())) {
        discriminator = processDiscriminatorElement(resultChild, typeClass, resultMappings);
      } else {
      
        List<ResultFlag> flags = new ArrayList<>();
        // id
        if ("id".equals(resultChild.getName())) {
          flags.add(ResultFlag.ID);
        }
        // 构建成resultMapping 添加到 List<ResultMapping> resultMappings
        resultMappings.add(buildResultMappingFromContext(resultChild, typeClass, flags));
      }
    }
    
    // Id  extends  automapping属性处理
    String id = resultMapNode.getStringAttribute("id",
            resultMapNode.getValueBasedIdentifier());
    String extend = resultMapNode.getStringAttribute("extends");
    Boolean autoMapping = resultMapNode.getBooleanAttribute("autoMapping");
    // 构建成ResultMapResolver对象
    ResultMapResolver resultMapResolver = new ResultMapResolver(builderAssistant, id, typeClass, extend, discriminator, resultMappings, autoMapping);
    try {
        // 将resultmapping加入到configuration主配置中的resultMaps集合
      return resultMapResolver.resolve();
    } catch (IncompleteElementException  e) {
      configuration.addIncompleteResultMap(resultMapResolver);
      throw e;
    }
  }

3️⃣sql语句
private void sqlElement(List<XNode> list) {
    if (configuration.getDatabaseId() != null) {
      sqlElement(list, configuration.getDatabaseId());
    }
    sqlElement(list, null);
  }

  private void sqlElement(List<XNode> list, String requiredDatabaseId) {
    for (XNode context : list) {
      String databaseId = context.getStringAttribute("databaseId");
      // 获取sql标签的id属性
      String id = context.getStringAttribute("id");
      // id 修改为 => namespace.id
      id = builderAssistant.applyCurrentNamespace(id, false);
      // 判断是否已经存在id，不存在继续执行代码，存在则
      if (databaseIdMatchesCurrent(id, databaseId, requiredDatabaseId)) {
      // XMLMapperBuilder类的属性sqlFragments 集合存储basesql配置信息
        sqlFragments.put(id, context);
      }
    }
  }

4️⃣ 根据语句类型构建
private void buildStatementFromContext(List<XNode> list) {
    if (configuration.getDatabaseId() != null) {
        buildStatementFromContext(list, configuration.getDatabaseId());
    }
    buildStatementFromContext(list, null);
}

 private void buildStatementFromContext(List<XNode> list) {
    if (configuration.getDatabaseId() != null) {
      buildStatementFromContext(list, configuration.getDatabaseId());
    }
    buildStatementFromContext(list, null);
  }

 private void buildStatementFromContext(List<XNode> list, String requiredDatabaseId) {
    for (XNode context : list) {
    // 根据sql语句构建 XMLStatementBuilder实例
      final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId);
      try {
      // 解析
        statementParser.parseStatementNode();
      } catch (IncompleteElementException e) {
        configuration.addIncompleteStatement(statementParser);
      }
    }
  }

public void parseStatementNode() {
    // 获取id  databaseId
    String id = context.getStringAttribute("id");
    String databaseId = context.getStringAttribute("databaseId");

    // 将id名改为nasespace.id 的形式，并判断id是否重复，重复，就return
    if (!databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) {
      return;
    }

    // 获取dom  select|update|delete|insert，转为大写字母
    String nodeName = context.getNode().getNodeName();
    SqlCommandType sqlCommandType = SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH));
    // 是否是查询 
    boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
    // 刷新缓存， 是查询，就为false
    boolean flushCache = context.getBooleanAttribute("flushCache", !isSelect);
    // 查询 使用缓存
    boolean useCache = context.getBooleanAttribute("useCache", isSelect);
    // 排序
    boolean resultOrdered = context.getBooleanAttribute("resultOrdered", false);

    // Include Fragments before parsing
    XMLIncludeTransformer includeParser = new XMLIncludeTransformer(configuration, builderAssistant);
    includeParser.applyIncludes(context.getNode());
    // 获取参数类型
    String parameterType = context.getStringAttribute("parameterType");
    // 加载参数
    Class<?> parameterTypeClass = resolveClass(parameterType);

    String lang = context.getStringAttribute("lang");
    LanguageDriver langDriver = getLanguageDriver(lang);

    // Parse selectKey after includes and remove them.
    processSelectKeyNodes(id, parameterTypeClass, langDriver);

    // Parse the SQL (pre: <selectKey> and <include> were parsed and removed)
    KeyGenerator keyGenerator;
    String keyStatementId = id + SelectKeyGenerator.SELECT_KEY_SUFFIX;
    keyStatementId = builderAssistant.applyCurrentNamespace(keyStatementId, true);
    if (configuration.hasKeyGenerator(keyStatementId)) {
      keyGenerator = configuration.getKeyGenerator(keyStatementId);
    } else {
      keyGenerator = context.getBooleanAttribute("useGeneratedKeys",
          configuration.isUseGeneratedKeys() && SqlCommandType.INSERT.equals(sqlCommandType))
          ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
    }

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

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

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 (unresolvedCacheRef) {
      throw new IncompleteElementException("Cache-ref not yet resolved");
    }

    id = applyCurrentNamespace(id, false);
    boolean isSelect = sqlCommandType == SqlCommandType.SELECT;

    // 构建builder对象
    MappedStatement.Builder statementBuilder = new MappedStatement.Builder(configuration, id, sqlSource, sqlCommandType)
        .resource(resource)
        .fetchSize(fetchSize)
        .timeout(timeout)
        .statementType(statementType)
        .keyGenerator(keyGenerator)
        .keyProperty(keyProperty)
        .keyColumn(keyColumn)
        .databaseId(databaseId)
        .lang(lang)
        .resultOrdered(resultOrdered)
        .resultSets(resultSets)
        .resultMaps(getStatementResultMaps(resultMap, resultType, id))
        .resultSetType(resultSetType)
        .flushCacheRequired(valueOrDefault(flushCache, !isSelect))
        .useCache(valueOrDefault(useCache, isSelect))
        .cache(currentCache);
    // 👇 parameterMap、parameterType、id 构建ParameterMap对象
    ParameterMap statementParameterMap = getStatementParameterMap(parameterMap, parameterType, id);
    if (statementParameterMap != null) {
      // mappedStatement.parameterMap = statementParameterMap
      statementBuilder.parameterMap(statementParameterMap);
    }


    // sql配置文件封装为MappedStatement
    MappedStatement statement = statementBuilder.build();
    // sql语句添加到MapperStatement中
    configuration.addMappedStatement(statement);
    return statement;
  }

private ParameterMap getStatementParameterMap(
      String parameterMapName,
      Class<?> parameterTypeClass,
      String statementId) {
    parameterMapName = applyCurrentNamespace(parameterMapName, true);
    ParameterMap parameterMap = null;
    if (parameterMapName != null) {
      try {
        parameterMap = configuration.getParameterMap(parameterMapName);
      } catch (IllegalArgumentException e) {
        throw new IncompleteElementException("Could not find parameter map " + parameterMapName, e);
      }
    } else if (parameterTypeClass != null) {
      List<ParameterMapping> parameterMappings = new ArrayList<>();
      parameterMap = new ParameterMap.Builder(
          configuration,
          statementId + "-Inline",
          parameterTypeClass,
          parameterMappings).build();
    }
    return parameterMap;
  }

这应该还不是全部代码。。太多了

• sql语句添加到MapperStatement中
• basesql配置信息在属性sqlFragments 集合存储
• resultMapping装在了Configuration对象的resultMaps中
• environment 数据库环境信息
  ...
  到这所有配置文件加载完毕。

Configuration装了所有的xml配置信息。

下篇看 LogLoginMapper mapper = session.getMapper(LogLoginMapper.class); 这一句话