Struts2.0 中支持的基本数据类的转换的类XWorkBasicConverter的分析
项目中Struts2.1.6不支持基本数据类型的自动转换，项目继而采用Struts2.1.8支持数据类型的基本原始数据类型的自动转换。主要原因在：XWork的版本原来xwork2.1.3 提供为xwork2.16 版本：
下面代码为xwork2.16版本的源码：
* <p/>
* XWork will automatically handle the most common type conversion for you. This includes support for converting to
* and from Strings for each of the following:
* <p/>
* <ul>
* <li>String</li>
* <li>boolean / Boolean</li>
* <li>char / Character</li>
* <li>int / Integer, float / Float, long / Long, double / Double</li>
* <li>dates - uses the SHORT format for the Locale associated with the current request</li>
* <li>arrays - assuming the individual strings can be coverted to the individual items</li>
* <li>collections - if not object type can be determined, it is assumed to be a String and a new ArrayList is
* created</li>
* </ul>
* <p/> Note that with arrays the type conversion will defer to the type of the array elements and try to convert each
* item individually. As with any other type conversion, if the conversion can't be performed the standard type
* conversion error reporting is used to indicate a problem occured while processing the type conversion.
* <p/>
public class XWorkBasicConverter extends DefaultTypeConverter ：
//转换器的重点转换的方面如下：
@Override
public Object convertValue(Map<String, Object> context, Object o, Member member, String s, Object value, Class toType) {
Object result = null;
if (value == null || toType.isAssignableFrom(value.getClass())) {
// no need to convert at all, right?
return value;
}
if (toType == String.class) {
/* the code below has been disabled as it causes sideffects in Struts2 (XW-512)
// if input (value) is a number then use special conversion method (XW-490)
Class inputType = value.getClass();
if (Number.class.isAssignableFrom(inputType)) {
result = doConvertFromNumberToString(context, value, inputType);
if (result != null) {
return result;
}
}*/
// okay use default string conversion
result = doConvertToString(context, value);
} else if (toType == boolean.class) {
result = doConvertToBoolean(value);
} else if (toType == Boolean.class) {
result = doConvertToBoolean(value);
} else if (toType.isArray()) {
result = doConvertToArray(context, o, member, s, value, toType);
} else if (Date.class.isAssignableFrom(toType)) {
result = doConvertToDate(context, value, toType);
} else if (Calendar.class.isAssignableFrom(toType)) {
Date dateResult = (Date) doConvertToDate(context, value, Date.class);
if (dateResult != null) {
Calendar calendar = Calendar.getInstance();
calendar.setTime(dateResult);
result = calendar;
}
} else if (Collection.class.isAssignableFrom(toType)) {
result = doConvertToCollection(context, o, member, s, value, toType);
} else if (toType == Character.class) {
result = doConvertToCharacter(value);
} else if (toType == char.class) {
result = doConvertToCharacter(value);
} else if (Number.class.isAssignableFrom(toType) || toType.isPrimitive()) {
result = doConvertToNumber(context, value, toType);
} else if (toType == Class.class) {
result = doConvertToClass(value);
}
if (result == null) {
if (value instanceof Object[]) {
Object[] array = (Object[]) value;
if (array.length >= 1) {
value = array[0];
} else {
value = null;
}
// let's try to convert the first element only
result = convertValue(context, o, member, s, value, toType);
} else if (!"".equals(value)) { // we've already tried the types we know
result = super.convertValue(context, value, toType);
}
if (result == null && value != null && !"".equals(value)) {
throw new XWorkException("Cannot create type " + toType + " from value " + value);
}
}
return result;
}
// 其中的一个数字类型的转换：有此可以看出支持红色的部分的哦：^_^
private Object doConvertToNumber(Map<String, Object> context, Object value, Class toType) {
if (value instanceof String) {
if (toType == BigDecimal.class) {
return new BigDecimal((String) value);
} else if (toType == BigInteger.class) {
return new BigInteger((String) value);
} else if (toType.isPrimitive()) {
Object convertedValue = super.convertValue(context, value, toType);
String stringValue = (String) value;
if (!isInRange((Number)convertedValue, stringValue, toType))
throw new XWorkException("Overflow or underflow casting: \"" + stringValue + "\" into class " + convertedValue.getClass().getName());
return convertedValue;
} else {
String stringValue = (String) value;
if (!toType.isPrimitive() && (stringValue == null || stringValue.length() == 0)) {
return null;
}
NumberFormat numFormat = NumberFormat.getInstance(getLocale(context));
ParsePosition parsePos = new ParsePosition(0);
if (isIntegerType(toType)) {
numFormat.setParseIntegerOnly(true);
}
numFormat.setGroupingUsed(true);
Number number = numFormat.parse(stringValue, parsePos);
if (parsePos.getIndex() != stringValue.length()) {
throw new XWorkException("Unparseable number: \"" + stringValue + "\" at position "
+ parsePos.getIndex());
} else {
if (!isInRange(number, stringValue, toType))
throw new XWorkException("Overflow or underflow casting: \"" + stringValue + "\" into class " + number.getClass().getName());
value = super.convertValue(context, number, toType);
}
}
} else if (value instanceof Object[]) {
Object[] objArray = (Object[]) value;
if (objArray.length == 1) {
return doConvertToNumber(context, objArray[0], toType);
}
}
// pass it through DefaultTypeConverter
return super.convertValue(context, value, toType);
}
//时间类型的转换：
private Object doConvertToDate(Map<String, Object> context, Object value, Class toType) {
Date result = null;
if (value instanceof String && value != null && ((String) value).length() > 0) {
String sa = (String) value;
Locale locale = getLocale(context);
DateFormat df = null;
if (java.sql.Time.class == toType) {
df = DateFormat.getTimeInstance(DateFormat.MEDIUM, locale);
} else if (java.sql.Timestamp.class == toType) {
Date check = null;
//支持的格式
SimpleDateFormat dtfmt = (SimpleDateFormat) DateFormat.getDateTimeInstance(DateFormat.SHORT,
DateFormat.MEDIUM,
locale);
SimpleDateFormat fullfmt = new SimpleDateFormat(dtfmt.toPattern() + MILLISECOND_FORMAT,
locale);
SimpleDateFormat dfmt = (SimpleDateFormat) DateFormat.getDateInstance(DateFormat.SHORT,
locale);
SimpleDateFormat[] fmts = {fullfmt, dtfmt, dfmt};
for (SimpleDateFormat fmt : fmts) {
try {
check = fmt.parse(sa);
df = fmt;
if (check != null) {
break;
}
} catch (ParseException ignore) {
}
}
} else if (java.util.Date.class == toType) {
Date check = null;
DateFormat[] dfs = getDateFormats(locale);
for (DateFormat df1 : dfs) {
try {
check = df1.parse(sa);
df = df1;
if (check != null) {
break;
}
}
catch (ParseException ignore) {
}
}
}
//final fallback for dates without time
if (df == null) {
df = DateFormat.getDateInstance(DateFormat.SHORT, locale);
}
try {
df.setLenient(false); // let's use strict parsing (XW-341)
result = df.parse(sa);
if (!(Date.class == toType)) {
try {
Constructor constructor = toType.getConstructor(new Class[]{long.class});
return constructor.newInstance(new Object[]{Long.valueOf(result.getTime())});
} catch (Exception e) {
throw new XWorkException("Couldn't create class " + toType + " using default (long) constructor", e);
}
}
} catch (ParseException e) {
throw new XWorkException("Could not parse date", e);
}
} else if (Date.class.isAssignableFrom(value.getClass())) {
result = (Date) value;
}
return result;
}
//Struts2.0可以格式化的几种类型：
private DateFormat[] getDateFormats(Locale locale) {
DateFormat dt1 = DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.LONG, locale);
DateFormat dt2 = DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.MEDIUM, locale);
DateFormat dt3 = DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.SHORT, locale);
DateFormat d1 = DateFormat.getDateInstance(DateFormat.SHORT, locale);
DateFormat d2 = DateFormat.getDateInstance(DateFormat.MEDIUM, locale);
DateFormat d3 = DateFormat.getDateInstance(DateFormat.LONG, locale);
DateFormat rfc3399 = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
DateFormat[] dfs = {dt1, dt2, dt3, rfc3399, d1, d2, d3}; //added RFC 3339 date format (XW-473)
return dfs;
}