本文主要用于记录XStream的使用方式，特别是其中的“对象默认值”和Map转换器的使用

1，添加Maven依赖

<dependency><groupId>com.thoughtworks.xstream</groupId><artifactId>xstream</artifactId><version>1.4.11.1</version>
</dependency>

2，创建可以使用默认值的对象

import java.lang.reflect.Field;import com.thoughtworks.xstream.converters.reflection.ObjectAccessException;
import com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider;public class FieldDefaultValueProvider extends PureJavaReflectionProvider {/*** @param object 目标类的实例* @param fieldName XML中显示指明的字段* @param definedIn 父类或者类本身*/@Override  public void writeField(Object object, String fieldName, Object value, Class definedIn) {Field field = fieldDictionary.field(object.getClass(), fieldName, definedIn);//返回存在于xml中的字段  validateFieldAccess(field);//验证字段可以被访问 try {  if (value instanceof String) {String trim = ((String)value).trim();//字符串首尾去空if(trim.length()==0)//如果是空字符串，则不做赋值，使用默认初始值return;field.set(object,trim);  }else{field.set(object, value);  }} catch (IllegalArgumentException e) {  throw new ObjectAccessException("Could not set field " + object.getClass() + "." + field.getName(), e);  } catch (IllegalAccessException e) {  throw new ObjectAccessException("Could not set field " + object.getClass() + "." + field.getName(), e);  }  }
}

3，创建用于转换Map的对象

import java.util.HashMap;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter;
import com.thoughtworks.xstream.io.ExtendedHierarchicalStreamWriterHelper;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
import com.thoughtworks.xstream.mapper.Mapper;public class MapCustomConverter extends AbstractCollectionConverter {public MapCustomConverter(Mapper mapper) {super(mapper);}@Overridepublic boolean canConvert(Class type) {return type.equals(HashMap.class) || type.equals(Hashtable.class)|| type.getName().equals("java.util.LinkedHashMap") || type.getName().equals("sun.font.AttributeMap");}@Overridepublic void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) {Map map = (Map) source;for (Iterator iterator = map.entrySet().iterator(); iterator.hasNext();) {Entry entry = (Entry) iterator.next();ExtendedHierarchicalStreamWriterHelper.startNode(writer, "property", Entry.class);writer.addAttribute("key", entry.getKey().toString());writer.addAttribute("value", entry.getValue().toString());writer.endNode();}}@Overridepublic Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {Map map = (Map) createCollection(context.getRequiredType());populateMap(reader, context, map);return map;}protected void populateMap(HierarchicalStreamReader reader, UnmarshallingContext context, Map map) {while (reader.hasMoreChildren()) {reader.moveDown();Object key = reader.getAttribute("key");Object value = reader.getAttribute("value");map.put(key, value);reader.moveUp();}}
}

4，创建XStream对象

private static XStream getXStream() {XStream xstream = new XStream(new FieldDefaultValueProvider(),new DomDriver());// 创建Xstram对象xstream.autodetectAnnotations(true);xstream.registerConverter(new MapCustomConverter(new DefaultMapper(new ClassLoaderReference(XStream.class.getClassLoader()))));XStream.setupDefaultSecurity(xstream);xstream.allowTypes(new Class[] { CollectTaskMeta.class, FtpConfig.class, TaskParallel.class,TaskRootConfig.class, Sql.class });xstream.processAnnotations(new Class[] { CollectTaskMeta.class, FtpConfig.class, TaskParallel.class,TaskRootConfig.class, Sql.class });return xstream;}

5，使用XStream来解析文件

import org.springframework.util.ResourceUtils;XStream xstream = getXStream();
TaskRootConfig meteInfo = null;
try {meteInfo = (TaskRootConfig) xstream.fromXML(ResourceUtils.getFile("classpath:taskconfig.xml"));
} catch (FileNotFoundException e) {e.printStackTrace();
}