功能

就是把1条<select></select> 或 <insert/> 等变成1个MappedStatement

spring-mybatis方式

SqlSessionFactoryBean

protected SqlSessionFactory buildSqlSessionFactory() throws Exception {......................// 如果配置了mybatis.mapper-locationsif (this.mapperLocations != null) {      if (this.mapperLocations.length == 0) {        LOGGER.warn(() -> "Property 'mapperLocations' was specified but matching resources are not found.");      } else {        for (Resource mapperLocation : this.mapperLocations) {          if (mapperLocation == null) {            continue;          }          try {            XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(mapperLocation.getInputStream(),                targetConfiguration, mapperLocation.toString(), targetConfiguration.getSqlFragments());            xmlMapperBuilder.parse();          } catch (Exception e) {            throw new NestedIOException("Failed to parse mapping resource: '" + mapperLocation + "'", e);          } finally {            ErrorContext.instance().reset();          }          LOGGER.debug(() -> "Parsed mapper file: '" + mapperLocation + "'");        }      }    }......................}

xml方式

XMLStatementBuilder

解析xml文件中各个节点，比如<select/>、<insert/>、<update/>、<delete/>节点，内部会使用XMLScriptBuilder处理节点的sql部分，

每个节点（<select/>、<insert/>、<update/>、<delete/>）会生成1个MappedStatement，然后会放到Configuration的mappedStatements中

添加Mapper

private void bindMapperForNamespace() {    String namespace = builderAssistant.getCurrentNamespace();    if (namespace != null) {      Class
    boundType = null;      try {        boundType = Resources.classForName(namespace);      } catch (ClassNotFoundException e) {        //ignore, bound type is not required      }      if (boundType != null) {        if (!configuration.hasMapper(boundType)) {          // Spring may not know the real resource name so we set a flag          // to prevent loading again this resource from the mapper interface          // look at MapperAnnotationBuilder#loadXmlResource          configuration.addLoadedResource("namespace:" + namespace);          configuration.addMapper(boundType); //添加Mapper        }      }    }  }

MapperRegistry

public 
   
     void addMapper(Class
    
      type) {    if (type.isInterface()) {      if (hasMapper(type)) {        throw new BindingException("Type " + type + " is already known to the MapperRegistry.");      }      boolean loadCompleted = false;      try {        knownMappers.put(type, new MapperProxyFactory<>(type));        // It's important that the type is added before the parser is run        // otherwise the binding may automatically be attempted by the        // mapper parser. If the type is already known, it won't try.        MapperAnnotationBuilder parser = new MapperAnnotationBuilder(config, type);        parser.parse();        loadCompleted = true;      } finally {        if (!loadCompleted) {          knownMappers.remove(type);        }      }    }  }

MappedStatement

public final class MappedStatement {  private String resource; // file [E:\zyzhworkspace\springboot2\database\mybatis\mybatis-mapper\target\classes\com\kq\mybatis\mapper\AccountXmlMapper.xml]  private Configuration configuration;  private String id;  private Integer fetchSize;  private Integer timeout;  private StatementType statementType; //STATEMENT, PREPARED, CALLABLE  private ResultSetType resultSetType;  private SqlSource sqlSource;  private Cache cache;  private ParameterMap parameterMap;  private List
   
     resultMaps;  private boolean flushCacheRequired;  private boolean useCache;  private boolean resultOrdered;  private SqlCommandType sqlCommandType; // UNKNOWN, INSERT, UPDATE, DELETE, SELECT, FLUSH;  private KeyGenerator keyGenerator;  private String[] keyProperties;  private String[] keyColumns;  private boolean hasNestedResultMaps;  private String databaseId;  private Log statementLog;  private LanguageDriver lang;  private String[] resultSets;}

MapperBuilderAssistant

addMappedStatement

public MappedStatement addMappedStatement(..........................MappedStatement statement = statementBuilder.build();    configuration.addMappedStatement(statement); // 放到configuration mappedStatements.put(ms.getId(), ms);// id比如: com.kq.mybatis.mapper.AccountXmlMapper.getAccountList    return statement;}

注解方式

MapperAnnotationBuilder

解析注解(Select、Insert、Update、Delete)生成1个MappedStatement，然后会放到Configuration的mappedStatements中

parse

public void parse() {    String resource = type.toString();    if (!configuration.isResourceLoaded(resource)) {      loadXmlResource(); // 从xml加载，有可能没有xml的mapper文件的      configuration.addLoadedResource(resource); // hashset 不会重复添加      assistant.setCurrentNamespace(type.getName()); // 设置namespace      parseCache();      parseCacheRef();      Method[] methods = type.getMethods(); // 获得方法      for (Method method : methods) {        try {          // issue #237          if (!method.isBridge()) {            parseStatement(method);          }        } catch (IncompleteElementException e) {          configuration.addIncompleteMethod(new MethodResolver(this, method));        }      }    }    parsePendingMethods();  }

parseStatement

void parseStatement(Method method) {    Class
    parameterTypeClass = getParameterType(method);    LanguageDriver languageDriver = getLanguageDriver(method);    SqlSource sqlSource = getSqlSourceFromAnnotations(method, parameterTypeClass, languageDriver);    if (sqlSource != null) {      Options options = method.getAnnotation(Options.class);      final String mappedStatementId = type.getName() + "." + method.getName(); // 比如: com.kq.mybatis.mapper.AccountMapper.getAccountList      Integer fetchSize = null;      Integer timeout = null;      StatementType statementType = StatementType.PREPARED;      ResultSetType resultSetType = configuration.getDefaultResultSetType();      SqlCommandType sqlCommandType = getSqlCommandType(method);      boolean isSelect = sqlCommandType == SqlCommandType.SELECT;      boolean flushCache = !isSelect;      boolean useCache = isSelect;      KeyGenerator keyGenerator;      String keyProperty = null;      String keyColumn = null;      if (SqlCommandType.INSERT.equals(sqlCommandType) || SqlCommandType.UPDATE.equals(sqlCommandType)) {        // first check for SelectKey annotation - that overrides everything else        SelectKey selectKey = method.getAnnotation(SelectKey.class);        if (selectKey != null) {          keyGenerator = handleSelectKeyAnnotation(selectKey, mappedStatementId, getParameterType(method), languageDriver);          keyProperty = selectKey.keyProperty();        } else if (options == null) {          keyGenerator = configuration.isUseGeneratedKeys() ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;        } else {          keyGenerator = options.useGeneratedKeys() ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;          keyProperty = options.keyProperty();          keyColumn = options.keyColumn();        }      } else {        keyGenerator = NoKeyGenerator.INSTANCE; // 没有KeyGenerator 排除Insert和Update      }      if (options != null) {        if (FlushCachePolicy.TRUE.equals(options.flushCache())) {          flushCache = true;        } else if (FlushCachePolicy.FALSE.equals(options.flushCache())) {          flushCache = false;        }        useCache = options.useCache();        fetchSize = options.fetchSize() > -1 || options.fetchSize() == Integer.MIN_VALUE ? options.fetchSize() : null; //issue #348        timeout = options.timeout() > -1 ? options.timeout() : null;        statementType = options.statementType();        if (options.resultSetType() != ResultSetType.DEFAULT) {          resultSetType = options.resultSetType();        }      }      String resultMapId = null; // 比如: com.kq.mybatis.mapper.AccountMapper.getAccountList-void      ResultMap resultMapAnnotation = method.getAnnotation(ResultMap.class);      if (resultMapAnnotation != null) {        resultMapId = String.join(",", resultMapAnnotation.value());      } else if (isSelect) {        resultMapId = parseResultMap(method);      }      assistant.addMappedStatement(          mappedStatementId,          sqlSource,          statementType,          sqlCommandType,          fetchSize,          timeout,          // ParameterMapID          null,          parameterTypeClass,          resultMapId,          getReturnType(method),          resultSetType,          flushCache,          useCache,          // TODO gcode issue #577          false,          keyGenerator,          keyProperty,          keyColumn,          // DatabaseID          null,          languageDriver,          // ResultSets          options != null ? nullOrEmpty(options.resultSets()) : null);    }  }