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
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@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
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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); 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
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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
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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
以上这篇Java中Boolean与字符串或者数字1和0的转换实例就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持服务器之家。
