Spring JDBC查询返回对象代码跟踪

public <T> T query(final String sql, final ResultSetExtractor<T> rse) throws DataAccessException {
		Assert.notNull(sql, "SQL must not be null");
		Assert.notNull(rse, "ResultSetExtractor must not be null");
		if (logger.isDebugEnabled()) {
			logger.debug("Executing SQL query [" + sql + "]");
		}
		class QueryStatementCallback implements StatementCallback<T>, SqlProvider {
			public T doInStatement(Statement stmt) throws SQLException {
				ResultSet rs = null;
				try {
					rs = stmt.executeQuery(sql);
					ResultSet rsToUse = rs;
					if (nativeJdbcExtractor != null) {
						rsToUse = nativeJdbcExtractor.getNativeResultSet(rs);
					}
					return rse.extractData(rsToUse);
				}
				finally {
					JdbcUtils.closeResultSet(rs);
				}
			}
			public String getSql() {
				return sql;
			}
		}
		return execute(new QueryStatementCallback());
	}

public <T> List<T> query(String sql, RowMapper<T> rowMapper) throws DataAccessException {
		return query(sql, new RowMapperResultSetExtractor<T>(rowMapper));
	}

public List<T> extractData(ResultSet rs) throws SQLException {
		List<T> results = (this.rowsExpected > 0 ? new ArrayList<T>(this.rowsExpected) : new ArrayList<T>());
		int rowNum = 0;
		while (rs.next()) {
			results.add(this.rowMapper.mapRow(rs, rowNum++));
		}
		return results;
	}

public BeanPropertyRowMapper(Class<T> mappedClass) {
		initialize(mappedClass);
	}
protected void initialize(Class<T> mappedClass) {
		this.mappedClass = mappedClass;
		this.mappedFields = new HashMap<String, PropertyDescriptor>();
		this.mappedProperties = new HashSet<String>();
		PropertyDescriptor[] pds = BeanUtils.getPropertyDescriptors(mappedClass);
		for (PropertyDescriptor pd : pds) {
			if (pd.getWriteMethod() != null) {
				this.mappedFields.put(pd.getName().toLowerCase(), pd);
				String underscoredName = underscoreName(pd.getName());
				if (!pd.getName().toLowerCase().equals(underscoredName)) {
					this.mappedFields.put(underscoredName, pd);
				}
				this.mappedProperties.add(pd.getName());
			}
		}
	}

public T mapRow(ResultSet rs, int rowNumber) throws SQLException {
		Assert.state(this.mappedClass != null, "Mapped class was not specified");
		T mappedObject = BeanUtils.instantiate(this.mappedClass);
		BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(mappedObject);
		initBeanWrapper(bw);

		ResultSetMetaData rsmd = rs.getMetaData();
		int columnCount = rsmd.getColumnCount();
		Set<String> populatedProperties = (isCheckFullyPopulated() ? new HashSet<String>() : null);

		for (int index = 1; index <= columnCount; index++) {
			String column = JdbcUtils.lookupColumnName(rsmd, index);
			PropertyDescriptor pd = this.mappedFields.get(column.replaceAll(" ", "").toLowerCase());
			if (pd != null) {
				try {
					Object value = getColumnValue(rs, index, pd);
					if (logger.isDebugEnabled() && rowNumber == 0) {
						logger.debug("Mapping column ‘" + column + "‘ to property ‘" +
								pd.getName() + "‘ of type " + pd.getPropertyType());
					}
					try {
						bw.setPropertyValue(pd.getName(), value);
					}
					catch (TypeMismatchException e) {
						if (value == null && primitivesDefaultedForNullValue) {
							logger.debug("Intercepted TypeMismatchException for row " + rowNumber +
									" and column ‘" + column + "‘ with value " + value +
									" when setting property ‘" + pd.getName() + "‘ of type " + pd.getPropertyType() +
									" on object: " + mappedObject);
						}
						else {
							throw e;
						}
					}
					if (populatedProperties != null) {
						populatedProperties.add(pd.getName());
					}
				}
				catch (NotWritablePropertyException ex) {
					throw new DataRetrievalFailureException(
							"Unable to map column " + column + " to property " + pd.getName(), ex);
				}
			}
		}

		if (populatedProperties != null && !populatedProperties.equals(this.mappedProperties)) {
			throw new InvalidDataAccessApiUsageException("Given ResultSet does not contain all fields " +
					"necessary to populate object of class [" + this.mappedClass + "]: " + this.mappedProperties);
		}

		return mappedObject;
	}