看看XStream注解

前文展示了使用别名更改XML展示内容，在这一节，可以使用注解更简单的更改XML展示。

（1）最简单的注解示例

1. 输出响应消息

packagecom.favccxx.favsoft.pojo;
publicclassResponseMessage{
privateintmessageType;
privateStringmessageContent;
publicResponseMessage(intmessageType,StringmessageContent){
this.messageType=messageType;
this.messageContent=messageContent;
}
publicintgetMessageType(){
returnmessageType;
}
publicvoidsetMessageType(intmessageType){
this.messageType=messageType;
}
publicStringgetMessageContent(){
returnmessageContent;
}
publicvoidsetMessageContent(StringmessageContent){
this.messageContent=messageContent;
}
}

2. 开始测试

packagecom.favccxx.favsoft.main;
importcom.favccxx.favsoft.pojo.ResponseMessage;
importcom.thoughtworks.xstream.XStream;
publicclassMainAnnotations{
publicstaticvoidmain(String[]args){
XStreamstream=newXStream();
ResponseMessagemsg=newResponseMessage(200,"成功");
System.out.println(stream.toXML(msg));
}
}

3. 测试结果

<com.favccxx.favsoft.pojo.ResponseMessage>
<messageType>200</messageType>
<messageContent>成功</messageContent>
</com.favccxx.favsoft.pojo.ResponseMessage>

4. 使用注解后的输出内容

packagecom.favccxx.favsoft.pojo;
importcom.thoughtworks.xstream.annotations.XStreamAlias;
@XStreamAlias("message")
publicclassResponseMessage{
@XStreamAlias("type")
privateintmessageType;
@XStreamAlias("content")
privateStringmessageContent;
publicResponseMessage(intmessageType,StringmessageContent){
this.messageType=messageType;
this.messageContent=messageContent;
}
publicintgetMessageType(){
returnmessageType;
}
publicvoidsetMessageType(intmessageType){
this.messageType=messageType;
}
publicStringgetMessageContent(){
returnmessageContent;
}
publicvoidsetMessageContent(StringmessageContent){
this.messageContent=messageContent;
}
}

xstream.processAnnotations(ResponseMessage.class);

<message>
<type>200</type>
<content>成功</content>
</message>

（2）使用集合注解

2.1 响应消息对象

packagecom.favccxx.favsoft.pojo;
importjava.util.Arrays;
importjava.util.List;
importcom.thoughtworks.xstream.annotations.XStreamAlias;
@XStreamAlias("message")
publicclassResponseMessage{
@XStreamAlias("type")
privateintmessageType;
@XStreamAlias("content")
privateList<String>messageContent;
publicResponseMessage(intmessageType,String...messageContent){
this.messageType=messageType;
this.messageContent=Arrays.asList(messageContent);
}
publicintgetMessageType(){
returnmessageType;
}
publicvoidsetMessageType(intmessageType){
this.messageType=messageType;
}
publicList<String>getMessageContent(){
returnmessageContent;
}
publicvoidsetMessageContent(List<String>messageContent){
this.messageContent=messageContent;
}
}

2.2 开始测试

packagecom.favccxx.favsoft.main;
importcom.favccxx.favsoft.pojo.ResponseMessage;
importcom.thoughtworks.xstream.XStream;
publicclassMainAnnotations{
publicstaticvoidmain(String[]args){
XStreamxstream=newXStream();
xstream.processAnnotations(ResponseMessage.class);
ResponseMessagemsg=newResponseMessage(28,"终于爬上来了！","我忘带钥匙了！！！");
System.out.println(xstream.toXML(msg));
}
}

2.3 输出结果

<message>
<type>28</type>
<contentclass="java.util.Arrays$ArrayList">
<aclass="string-array">
<string>终于爬上来了！</string>
<string>我忘带钥匙了！！！</string>
</a>
</content>
</message>

2.4使用@XStreamImplicit注解将集合标记为隐式集合

packagecom.favccxx.favsoft.pojo;
importjava.util.Arrays;
importjava.util.List;
importcom.thoughtworks.xstream.annotations.XStreamAlias;
importcom.thoughtworks.xstream.annotations.XStreamImplicit;
@XStreamAlias("message")
publicclassResponseMessage{
@XStreamAlias("type")
privateintmessageType;
@XStreamImplicit
privateList<String>messageContent;
publicResponseMessage(intmessageType,String...messageContent){
this.messageType=messageType;
this.messageContent=Arrays.asList(messageContent);
}
publicintgetMessageType(){
returnmessageType;
}
publicvoidsetMessageType(intmessageType){
this.messageType=messageType;
}
publicList<String>getMessageContent(){
returnmessageContent;
}
publicvoidsetMessageContent(List<String>messageContent){
this.messageContent=messageContent;
}
}

2.5 输出结果

<message>
<type>28</type>
<string>终于爬上来了！</string>
<string>我忘带钥匙了！！！</string>
</message>

2.6 在原有注解对象上，对字段进行别名

packagecom.favccxx.favsoft.pojo;
importjava.util.Arrays;
importjava.util.List;
importcom.thoughtworks.xstream.annotations.XStreamAlias;
importcom.thoughtworks.xstream.annotations.XStreamImplicit;
@XStreamAlias("message")
publicclassResponseMessage{
@XStreamAlias("type")
privateintmessageType;
@XStreamImplicit(itemFieldName="dialog")
privateList<String>messageContent;
publicResponseMessage(intmessageType,String...messageContent){
this.messageType=messageType;
this.messageContent=Arrays.asList(messageContent);
}
publicintgetMessageType(){
returnmessageType;
}
publicvoidsetMessageType(intmessageType){
this.messageType=messageType;
}
publicList<String>getMessageContent(){
returnmessageContent;
}
publicvoidsetMessageContent(List<String>messageContent){
this.messageContent=messageContent;
}
}

2.7 输出内容如下

<message>
<type>28</type>
<dialog>终于爬上来了！</dialog>
<dialog>我忘带钥匙了！！！</dialog>
</message>

（3）属性别名

3.1响应消息

packagecom.favccxx.favsoft.pojo;
importjava.util.Arrays;
importjava.util.List;
importcom.thoughtworks.xstream.annotations.XStreamAlias;
importcom.thoughtworks.xstream.annotations.XStreamAsAttribute;
importcom.thoughtworks.xstream.annotations.XStreamConverter;
importcom.thoughtworks.xstream.annotations.XStreamImplicit;
importcom.thoughtworks.xstream.converters.basic.BooleanConverter;
@XStreamAlias("message")
publicclassResponseMessage{
@XStreamAlias("type")
@XStreamAsAttribute
privateintmessageType;
@XStreamImplicit(itemFieldName="dialog")
privateList<String>messageContent;
@XStreamAsAttribute
@XStreamConverter(value=BooleanConverter.class,booleans={false},strings={"yes","no"})
privatebooleanimportant;
publicResponseMessage(intmessageType,booleanimportant,String...messageContent){
this.messageType=messageType;
this.messageContent=Arrays.asList(messageContent);
this.important=important;
}
publicintgetMessageType(){
returnmessageType;
}
publicvoidsetMessageType(intmessageType){
this.messageType=messageType;
}
publicList<String>getMessageContent(){
returnmessageContent;
}
publicvoidsetMessageContent(List<String>messageContent){
this.messageContent=messageContent;
}
}

3.2输出内容

<messagetype="28"important="yes">
<dialog>终于爬上来了！</dialog>
<dialog>我忘带钥匙了！！！</dialog>
</message>

（4）所有字段变为文本，值得注意的是，转换为文本的内容，只能是String类型的，因为转换器是StringValueConvertor。

packagecom.favccxx.favsoft.pojo;
importcom.thoughtworks.xstream.annotations.XStreamAlias;
importcom.thoughtworks.xstream.annotations.XStreamConverter;
importcom.thoughtworks.xstream.converters.basic.BooleanConverter;
importcom.thoughtworks.xstream.converters.extended.ToAttributedValueConverter;
@XStreamAlias("message")
@XStreamConverter(value=ToAttributedValueConverter.class,strings={"messageContent"})
publicclassResponseMessage{
@XStreamAlias("type")
privateintmessageType;
@XStreamAlias("content")
privateStringmessageContent;
@XStreamConverter(value=BooleanConverter.class,StringmessageContent){
this.messageType=messageType;
this.messageContent=messageContent;
this.important=important;
}
publicintgetMessageType(){
returnmessageType;
}
publicvoidsetMessageType(intmessageType){
this.messageType=messageType;
}
publicStringgetMessageContent(){
returnmessageContent;
}
publicvoidsetMessageContent(StringmessageContent){
this.messageContent=messageContent;
}
publicbooleanisImportant(){
returnimportant;
}
publicvoidsetImportant(booleanimportant){
this.important=important;
}
}

<messagetype="200"important="yes">今天星期五</message>

（5）省略字段

packagecom.favccxx.favsoft.pojo;
importjava.util.Arrays;
importjava.util.List;
importcom.thoughtworks.xstream.annotations.XStreamAlias;
importcom.thoughtworks.xstream.annotations.XStreamConverter;
importcom.thoughtworks.xstream.annotations.XStreamImplicit;
importcom.thoughtworks.xstream.annotations.XStreamOmitField;
importcom.thoughtworks.xstream.converters.basic.BooleanConverter;
@XStreamAlias("message")
publicclassResponseMessage{
@XStreamOmitField
privateintmessageType;
@XStreamImplicit(itemFieldName="content")
privateList<String>messageContent;
@XStreamConverter(value=BooleanConverter.class,String...messageContent){
this.messageType=messageType;
this.important=important;
this.messageContent=Arrays.asList(messageContent);
}
publicintgetMessageType(){
returnmessageType;
}
publicvoidsetMessageType(intmessageType){
this.messageType=messageType;
}
publicList<String>getMessageContent(){
returnmessageContent;
}
publicvoidsetMessageContent(List<String>messageContent){
this.messageContent=messageContent;
}
publicbooleanisImportant(){
returnimportant;
}
publicvoidsetImportant(booleanimportant){
this.important=important;
}
}

<message>
<content>今天星期五</content>
<content>明天去逛街</content>
<important>yes</important>
</message>

（6）自动检测注解

可以使用下述方法自动检测注解，而不用每次都为每个类设置注解

xstream.autodetectAnnotations(true);
//xstream.processAnnotations(ResponseMessage.class);

总结：使用注解比别名方便易用，但是当一个类被多次重用时，使用别名会更明智些。

（编辑：李大同）

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