mybatis源码之MapperMethod

/** * @author Clinton Begin * @author Eduardo Macarron * @author Lasse Voss *///这个类是整个代理机制的核心类，对Sqlsession当中的操作进行了封装public class MapperMethod {  //一个内部封 封装了SQL标签的类型 insert update delete select  private final SqlCommand command;  //一个内部类 封装了方法的参数信息 返回类型信息等  private final MethodSignature method;  //构造参数  public MapperMethod(Class<?> mapperInterface, Method method, Configuration config) {    this.command = new SqlCommand(config, mapperInterface, method);    this.method = new MethodSignature(config, method);  }  //这个方法是对SqlSession的包装调用  public Object execute(SqlSession sqlSession, Object[] args) {//定义返回结果    Object result;//如果是INSERT操作    if (SqlCommandType.INSERT == command.getType()) {  //处理参数      Object param = method.convertArgsToSqlCommandParam(args);  //调用sqlSession的insert方法      result = rowCountResult(sqlSession.insert(command.getName(), param));  //如果是UPDATE操作 同上    } else if (SqlCommandType.UPDATE == command.getType()) {      Object param = method.convertArgsToSqlCommandParam(args);      result = rowCountResult(sqlSession.update(command.getName(), param));  //如果是DELETE操作 同上    } else if (SqlCommandType.DELETE == command.getType()) {      Object param = method.convertArgsToSqlCommandParam(args);      result = rowCountResult(sqlSession.delete(command.getName(), param));  //如果是SELECT操作 那么情况会多一些 但是也都和sqlSession的查询方法一一对应    } else if (SqlCommandType.SELECT == command.getType()) {   //如果返回void 并且参数有resultHandler      //则调用 void select(String statement, Object parameter, ResultHandler handler);方法      if (method.returnsVoid() && method.hasResultHandler()) {        executeWithResultHandler(sqlSession, args);        result = null;  //如果返回多行结果这调用 <E> List<E> selectList(String statement, Object parameter);      //executeForMany这个方法调用的      } else if (method.returnsMany()) {        result = executeForMany(sqlSession, args);  //如果返回类型是MAP 则调用executeForMap方法      } else if (method.returnsMap()) {        result = executeForMap(sqlSession, args);      } else {//否则就是查询单个对象        Object param = method.convertArgsToSqlCommandParam(args);        result = sqlSession.selectOne(command.getName(), param);      }    } else if (SqlCommandType.FLUSH == command.getType()) {        result = sqlSession.flushStatements();    } else {  //如果全都不匹配 说明mapper中定义的方法不对      throw new BindingException("Unknown execution method for: " + command.getName());    }//如果返回值为空 并且方法返回值类型是基础类型 并且不是VOID 则抛出异常    if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {      throw new BindingException("Mapper method '" + command.getName()           + " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");    }    return result;  }  private Object rowCountResult(int rowCount) {    final Object result;    if (method.returnsVoid()) {      result = null;    } else if (Integer.class.equals(method.getReturnType()) || Integer.TYPE.equals(method.getReturnType())) {      result = Integer.valueOf(rowCount);    } else if (Long.class.equals(method.getReturnType()) || Long.TYPE.equals(method.getReturnType())) {      result = Long.valueOf(rowCount);    } else if (Boolean.class.equals(method.getReturnType()) || Boolean.TYPE.equals(method.getReturnType())) {      result = Boolean.valueOf(rowCount > 0);    } else {      throw new BindingException("Mapper method '" + command.getName() + "' has an unsupported return type: " + method.getReturnType());    }    return result;  }  private void executeWithResultHandler(SqlSession sqlSession, Object[] args) {    MappedStatement ms = sqlSession.getConfiguration().getMappedStatement(command.getName());    if (void.class.equals(ms.getResultMaps().get(0).getType())) {      throw new BindingException("method " + command.getName()           + " needs either a @ResultMap annotation, a @ResultType annotation,"           + " or a resultType attribute in XML so a ResultHandler can be used as a parameter.");    }    Object param = method.convertArgsToSqlCommandParam(args);    if (method.hasRowBounds()) {      RowBounds rowBounds = method.extractRowBounds(args);      sqlSession.select(command.getName(), param, rowBounds, method.extractResultHandler(args));    } else {      sqlSession.select(command.getName(), param, method.extractResultHandler(args));    }  }  //返回多行结果 调用sqlSession.selectList方法  private <E> Object executeForMany(SqlSession sqlSession, Object[] args) {    List<E> result;    Object param = method.convertArgsToSqlCommandParam(args);//如果参数含有rowBounds则调用分页的查询    if (method.hasRowBounds()) {      RowBounds rowBounds = method.extractRowBounds(args);      result = sqlSession.<E>selectList(command.getName(), param, rowBounds);    } else {//没有分页则调用普通查询      result = sqlSession.<E>selectList(command.getName(), param);    }    // issue #510 Collections & arrays support    if (!method.getReturnType().isAssignableFrom(result.getClass())) {      if (method.getReturnType().isArray()) {        return convertToArray(result);      } else {        return convertToDeclaredCollection(sqlSession.getConfiguration(), result);      }    }    return result;  }  private <E> Object convertToDeclaredCollection(Configuration config, List<E> list) {    Object collection = config.getObjectFactory().create(method.getReturnType());    MetaObject metaObject = config.newMetaObject(collection);    metaObject.addAll(list);    return collection;  }  @SuppressWarnings("unchecked")  private <E> E[] convertToArray(List<E> list) {    E[] array = (E[]) Array.newInstance(method.getReturnType().getComponentType(), list.size());    array = list.toArray(array);    return array;  }  private <K, V> Map<K, V> executeForMap(SqlSession sqlSession, Object[] args) {    Map<K, V> result;    Object param = method.convertArgsToSqlCommandParam(args);    if (method.hasRowBounds()) {      RowBounds rowBounds = method.extractRowBounds(args);      result = sqlSession.<K, V>selectMap(command.getName(), param, method.getMapKey(), rowBounds);    } else {      result = sqlSession.<K, V>selectMap(command.getName(), param, method.getMapKey());    }    return result;  }  public static class ParamMap<V> extends HashMap<String, V> {    private static final long serialVersionUID = -2212268410512043556L;    @Override    public V get(Object key) {      if (!super.containsKey(key)) {        throw new BindingException("Parameter '" + key + "' not found. Available parameters are " + keySet());      }      return super.get(key);    }  }  //一个内部类 封装了具体执行的动作  public static class SqlCommand {//xml标签的id    private final String name;//insert update delete select的具体类型    private final SqlCommandType type;    public SqlCommand(Configuration configuration, Class<?> mapperInterface, Method method) {  //拿到全名 比如 org.mybatis.example.BlogMapper.selectBlog      String statementName = mapperInterface.getName() + "." + method.getName();      MappedStatement ms = null;  //获取MappedStatement对象 这个对象封装了XML当中一个标签的所有信息 比如下面      //<select id="selectBlog" resultType="Blog">      //select * from Blog where id = #{id}      //</select>      if (configuration.hasStatement(statementName)) {        ms = configuration.getMappedStatement(statementName);      } else if (!mapperInterface.equals(method.getDeclaringClass())) { // issue #35        String parentStatementName = method.getDeclaringClass().getName() + "." + method.getName();        if (configuration.hasStatement(parentStatementName)) {          ms = configuration.getMappedStatement(parentStatementName);        }      }  //为空抛出异常      if (ms == null) {        if(method.getAnnotation(Flush.class) != null){          name = null;          type = SqlCommandType.FLUSH;        } else {          throw new BindingException("Invalid bound statement (not found): " + statementName);        }      } else {        name = ms.getId();        type = ms.getSqlCommandType();//判断SQL标签类型 未知就抛异常        if (type == SqlCommandType.UNKNOWN) {          throw new BindingException("Unknown execution method for: " + name);        }      }    }    public String getName() {      return name;    }    public SqlCommandType getType() {      return type;    }  }  //内部类 封装了接口当中方法的 参数类型 返回值类型 等信息  public static class MethodSignature {//是否返回多调结果    private final boolean returnsMany;//返回值是否是MAP    private final boolean returnsMap;//返回值是否是VOID    private final boolean returnsVoid;//返回值类型    private final Class<?> returnType;//mapKey    private final String mapKey;//resultHandler类型参数的位置    private final Integer resultHandlerIndex;//rowBound类型参数的位置    private final Integer rowBoundsIndex;//用来存放参数信息    private final SortedMap<Integer, String> params;//是否存在命名参数    private final boolean hasNamedParameters;    public MethodSignature(Configuration configuration, Method method) {      this.returnType = method.getReturnType();      this.returnsVoid = void.class.equals(this.returnType);      this.returnsMany = (configuration.getObjectFactory().isCollection(this.returnType) || this.returnType.isArray());      this.mapKey = getMapKey(method);      this.returnsMap = (this.mapKey != null);      this.hasNamedParameters = hasNamedParams(method);      this.rowBoundsIndex = getUniqueParamIndex(method, RowBounds.class);      this.resultHandlerIndex = getUniqueParamIndex(method, ResultHandler.class);      this.params = Collections.unmodifiableSortedMap(getParams(method, this.hasNamedParameters));    }    public Object convertArgsToSqlCommandParam(Object[] args) {      final int paramCount = params.size();      if (args == null || paramCount == 0) {        return null;      } else if (!hasNamedParameters && paramCount == 1) {        return args[params.keySet().iterator().next().intValue()];      } else {        final Map<String, Object> param = new ParamMap<Object>();        int i = 0;        for (Map.Entry<Integer, String> entry : params.entrySet()) {          param.put(entry.getValue(), args[entry.getKey().intValue()]);          // issue #71, add param names as param1, param2...but ensure backward compatibility          final String genericParamName = "param" + String.valueOf(i + 1);          if (!param.containsKey(genericParamName)) {            param.put(genericParamName, args[entry.getKey()]);          }          i++;        }        return param;      }    }    public boolean hasRowBounds() {      return rowBoundsIndex != null;    }    public RowBounds extractRowBounds(Object[] args) {      return hasRowBounds() ? (RowBounds) args[rowBoundsIndex] : null;    }    public boolean hasResultHandler() {      return resultHandlerIndex != null;    }    public ResultHandler extractResultHandler(Object[] args) {      return hasResultHandler() ? (ResultHandler) args[resultHandlerIndex] : null;    }    public String getMapKey() {      return mapKey;    }    public Class<?> getReturnType() {      return returnType;    }    public boolean returnsMany() {      return returnsMany;    }    public boolean returnsMap() {      return returnsMap;    }    public boolean returnsVoid() {      return returnsVoid;    }    private Integer getUniqueParamIndex(Method method, Class<?> paramType) {      Integer index = null;      final Class<?>[] argTypes = method.getParameterTypes();      for (int i = 0; i < argTypes.length; i++) {        if (paramType.isAssignableFrom(argTypes[i])) {          if (index == null) {            index = i;          } else {            throw new BindingException(method.getName() + " cannot have multiple " + paramType.getSimpleName() + " parameters");          }        }      }      return index;    }    private String getMapKey(Method method) {      String mapKey = null;      if (Map.class.isAssignableFrom(method.getReturnType())) {        final MapKey mapKeyAnnotation = method.getAnnotation(MapKey.class);        if (mapKeyAnnotation != null) {          mapKey = mapKeyAnnotation.value();        }      }      return mapKey;    }    private SortedMap<Integer, String> getParams(Method method, boolean hasNamedParameters) {      final SortedMap<Integer, String> params = new TreeMap<Integer, String>();      final Class<?>[] argTypes = method.getParameterTypes();      for (int i = 0; i < argTypes.length; i++) {        if (!RowBounds.class.isAssignableFrom(argTypes[i]) && !ResultHandler.class.isAssignableFrom(argTypes[i])) {          String paramName = String.valueOf(params.size());          if (hasNamedParameters) {            paramName = getParamNameFromAnnotation(method, i, paramName);          }          params.put(i, paramName);        }      }      return params;    }    private String getParamNameFromAnnotation(Method method, int i, String paramName) {      final Object[] paramAnnos = method.getParameterAnnotations()[i];      for (Object paramAnno : paramAnnos) {        if (paramAnno instanceof Param) {          paramName = ((Param) paramAnno).value();          break;        }      }      return paramName;    }    private boolean hasNamedParams(Method method) {      final Object[][] paramAnnos = method.getParameterAnnotations();      for (Object[] paramAnno : paramAnnos) {        for (Object aParamAnno : paramAnno) {          if (aParamAnno instanceof Param) {            return true;          }        }      }      return false;    }  }}