Java中Boolean与字符串或者数字1和0的转换实例

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