xml如何在java SimpleXML中反序列化嵌套对象

Question

我有下面的xml，我想用simpleXML解析它

<programme start="20161107190000 GMT+04:00" stop="20161107200000 GMT+04:00" channel="001">
    <title lang="en_GB">Foo</title>
    <desc lang="en_GB">Foobarbaz</desc>
</programme>
<programme start="20161107200000 GMT+04:00" stop="20161107203000 GMT+04:00" channel="001">
    <title lang="en_GB">JLS</title>
    <desc lang="en_GB">The Java Language Specification</desc>
</programme>

有以下几点

@Root
public class Programme {

    @Attribute(name = "channel", required = false)
    private String channel;

    @Attribute(name = "start", required = false)
    private String start;

    @Attribute(name = "stop", required = false)
    private String stop;

    @Element(name = "title", required = false)
    private Title title;

    @Element(name = "desc", required = false)
    private String desc;

    public Programme(String channel, String start, String stop, String title, String desc) {
        this.channel = channel;
        this.start = start;
        this.stop = stop;
        this.title = title;
        this.desc = desc;
    }

    public String getChannel() {
        return channel;
    }

    public void setChannel(String channel) {
        this.channel = channel;
    }

    public String getStart() {
        return start;
    }

    public void setStart(String start) {
        this.start = start;
    }

    public String getStop() {
        return stop;
    }

    public void setStop(String stop) {
        this.stop = stop;
    }

    public Title getTitle() {
        return title;
    }

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

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }

    @Root(name = "title")
    public class Title {

        @Attribute
        private String lang;

        private String text;

        public Title(String lang, String text) {
            this.lang = lang;
            this.text = text;
        }

        public String getLang() {
            return lang;
        }

        public void setLang(String lang) {
            this.lang = lang;
        }

        @Text
        public String getText() {
            return text;
        }

        @Text
        public void setText(String text) {
            this.text = text;
        }
    }

}

给我错误org.simpleframework.xml.core.ConstructorException: Can not construct inner class

Answer 1

有几件事需要注意

1）如果内部元素中的属性有嵌套类，则嵌套类必须是static

2）为内部类定义变量时必须注释如下

@Element(name = "title", type = Title.class, required = false)
private Title title;

3）在构造函数中，他们应该实例化一个空类

this.title = new Title();

这是一个完整的工作版本：

@Root
public class Programme {


    @Attribute(name = "channel", required = false)
    private final String channel;

    @Attribute(name = "start", required = false)
    private final String start;

    @Attribute(name = "stop", required = false)
    private final String stop;


    @Element(name = "title", type = Title.class, required = false)
    private Title title;

    @Element(name = "desc", type = Desc.class, required = false)
    private Desc desc;

    public Programme(
            @Attribute(name = "channel") String channel,
            @Attribute(name = "start") String start,
            @Attribute(name = "stop") String stop
    ) {
        this.channel = channel;
        this.start = start;
        this.stop = stop;
        this.title = new Title();
        this.desc = new Desc();
    }

    public Title getTitle() {
        return title;
    }

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

    public Desc getDesc() {
        return desc;
    }

    public void setDesc(Desc desc) {
        this.desc = desc;
    }


    @Root(name = "title")
    public static class Title {
        public String text;
        @Attribute(name = "lang")
        private String lang;

        @Text
        public String getText() {
            return text;
        }

        @Text
        public void setText(String text) {
            this.text = text;
        }

        public String getLang() {
            return lang;
        }
    }

    @Root(name = "desc")
    public static class Desc {
        public String text;
        @Attribute(name = "lang")
        private String lang;

        @Text
        public String getText() {
            return text;
        }

        @Text
        public void setText(String text) {
            this.text = text;
        }

        public String getLang() {
            return lang;
        }
    }

}