java中boolean与字符串或者数字1和0的转换

mysql有个字段是bit，只存储1和0，是二进制存储，那么在java的dao层如何映射成boolean呢

@Column(name="is_standard")
private boolean isStandard;

public void setIsStandard(boolean isStandard){
   this.isStandard = isStandard;
}

public boolean getIsStandard(){
   return isStandard;
}

其实就是在底层dao做反射的时候，先判断字段(比如isStandard)的字段类型是否为boolean，如果是，则在查出数据库字段bit is_standard的时候，做转换

private List<T> populateData(ResultSet resultSet, Class<T> clazz) throws Exception {
		List<T> dataList = new ArrayList<T>();
		List<Field> fieldList = MappingAnnotationUtil.getAllFields(clazz);

		ResultSetMetaData rsmd = resultSet.getMetaData();
		int columnsCount = rsmd.getColumnCount();
		List<String> columnNameList = new ArrayList<String>();
		for(int i = 0; i < columnsCount; i++){
			columnNameList.add(rsmd.getColumnLabel(i+1).toLowerCase());
		}

		while (resultSet.next()) { 
			T bean = clazz.newInstance();
			for(Field f : fieldList) {
				String columnName = MappingAnnotationUtil.getDBCloumnName(clazz, f).toLowerCase();
				if(columnNameList.contains(columnName)) {
					Object columnValueObj = null;
					Class<?> filedCls = f.getType();
					
					if(filedCls == int.class || filedCls == Integer.class) {
						columnValueObj = resultSet.getInt(columnName);
					} else if(filedCls == String.class) {
						columnValueObj = resultSet.getString(columnName);
					} else if(filedCls == boolean.class || filedCls == Boolean.class) {
						columnValueObj = resultSet.getBoolean(columnName);
					} else if(filedCls == byte.class || filedCls == Byte.class) {
						columnValueObj = resultSet.getByte(columnName);
					} else if(filedCls == short.class || filedCls == Short.class) {
						columnValueObj = resultSet.getShort(columnName);
					} else if(filedCls == long.class || filedCls == Long.class) {
						columnValueObj = resultSet.getLong(columnName);
					} else if(filedCls == float.class || filedCls == Float.class) {
						columnValueObj = resultSet.getFloat(columnName);
					} else if(filedCls == double.class || filedCls == Double.class) {
						columnValueObj = resultSet.getDouble(columnName);
					} else if(filedCls == BigDecimal.class) {
						columnValueObj = resultSet.getBigDecimal(columnName);
					} 
					
					else {
						columnValueObj = resultSet.getObject(columnName);
					}
					
					if (columnValueObj != null) {
						Method setterMethod = MappingAnnotationUtil.getSetterMethod(clazz, f);
						setterMethod.invoke(bean, new Object[] { columnValueObj });
					}
				}
			}
			dataList.add(bean);
		}
		return dataList;
	}

注意这个

else if(filedCls == boolean.class || filedCls == Boolean.class) {
   columnValueObj = resultSet.getBoolean(columnName);
} 

resultSet.getBoolean(columnName) 就是转换的方法，具体实现为

 for (int i = 0; i < trueStrings.length; ++i) {
                if (trueStrings[i].equals(stringValue)) {
                    return type.cast(Boolean.TRUE);
                }
            }

            for (int i = 0; i < falseStrings.length; ++i) {
                if (falseStrings[i].equals(stringValue)) {
                    return type.cast(Boolean.FALSE);
                }
            }

核心原理就是根据字符串/数字做对比，如果是1,0就返回true/false，其它的直接返回false或抛出异常，字符串如果是[true, yes, y, on, 1]就返回true，如果是[false, no, n, off, 0]就返回false

@落雨
2015.09.12
http://luoyu.win
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