XStream:在分析时折叠XML层次结构

使用自定义转换器并不难。这是一个有点长的例子,但我希望它足够简单,以获得您需要做的事情的要点:

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.annotations.XStreamAlias;
import com.thoughtworks.xstream.converters.Converter;
import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;

public final class ConverterTest {
    public static void main(String[] args) {
        XStream xstream = new XStream();
        xstream.autodetectAnnotations(true);
        xstream.registerConverter(new PositionConverter());

        final Position position = new Position();
        position.setTitle("The Title");
        position.setStartDate("The Start Date");
        position.setEndDate("The End Date");

        final String xml = xstream.toXML(position);
        System.out.println("Generated XML:");
        System.out.println(xml);

        final Position genPosition = (Position) xstream.fromXML(xml);
        System.out.println("Generated Position:");
        System.out.println("\tTitle: " + genPosition.getTitle());
        System.out.println("\tStart Date: " + genPosition.getStartDate());
        System.out.println("\tEnd Date: " + genPosition.getEndDate());
    }

    @XStreamAlias("Position")
    private static class Position {
        public String getEndDate() {
            return endDate;
        }

        public void setEndDate(String endDate) {
            this.endDate = endDate;
        }

        public String getStartDate() {
            return startDate;
        }

        public void setStartDate(String startDate) {
            this.startDate = startDate;
        }

        public String getTitle() {
            return title;
        }

        public void setTitle(String title) {
            this.title = title;
        }

        private String title;
        private String startDate;
        private String endDate;
    }

    private static class PositionConverter implements Converter {
        public boolean canConvert(Class clazz) {
            return Position.class == clazz;
        }

        public void marshal(Object value, HierarchicalStreamWriter writer, MarshallingContext context) {
            Position position = (Position)value;
            writer.startNode("PositionBorder");

            writer.startNode("Title");
            writer.setValue(position.getTitle());
            writer.endNode();

            writer.startNode("StartDate");
            writer.setValue(position.getStartDate());
            writer.endNode();

            writer.startNode("EndDate");
            writer.setValue(position.getEndDate());
            writer.endNode();

            writer.endNode();
        }

        public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
            Position position = new Position();
            // move it to <PositionBorder> tag.
            reader.moveDown();
            // now move it to <Title> tag.
            reader.moveDown();
            String title = reader.getValue();
            position.setTitle(title);
            reader.moveUp(); // moves back to <PositionBorder>

            reader.moveDown(); // should move down to <StartDate> tag
            String startDate = reader.getValue();
            position.setStartDate(startDate);
            reader.moveUp(); // move back to <PositionBorder>

            reader.moveDown(); // should move down to <EndDate> tag
            String endDate = reader.getValue();
            position.setEndDate(endDate);
            reader.moveUp(); // move back to <PositionBorder>


            return position;
        }
    }
}

试着运行它,看看会发生什么。当然,您需要修改它以适合您自己的类型——我只是在position的所有字段中使用了字符串(我确信您的position类也没有嵌套),但是从字符串转换为日期(或其他)应该是非常简单的。

有件事你要注意(我可能还没弄到) 完全地 在我的示例中)正在匹配您的reader.movedown()和reader.moveup()调用。(而且,如果您要执行任何编组而不仅仅是解组(我不希望从您的问题中看到这一点),您还需要匹配writer.startnode()和writer.endnode()调用。)它可能不会对本例造成任何问题,但我相信如果您执行更大的操作或处理多个fil,它会引发问题。具有相同xstream或converter实例的。另外,如果您从一个无效的位置尝试reader.movedown(),您将得到一个非常糟糕的异常——这应该是非常明显的。

我必须在moveup/movedown方法中进行一些调整,以使它们处于正确的位置,所以我确信您需要测试和调整它,直到您得到所需的。

我发现这样更容易使用:

@Override
    public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
        Position mPosition = new Position();
        while (reader.hasMoreChildren()) {

            reader.moveDown();

            String nodeName = reader.getNodeName();

            if ("Title".equalsIgnoreCase(nodeName)) {
                mPosition.setTitle(reader.getValue());
            } else if ("StartDate".equalsIgnoreCase(nodeName)) {
                mPosition.setStartDate(reader.getValue());
            }else if ("attributeexample".equalsIgnoreCase(nodeName)) {
                mPosition.setAttributeExample(reader.getAttribute("attrname"));
            }

            reader.moveUp();
        }

        return mPosition;
    }