如何使用构建器类使用jaxb反序列化xml [英] How to deserialize xml with jaxb using builder class
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问题描述
我想用Jaxb并使用生成器类反序列化xml
I want to deserialize xml with Jaxb and using builder class
下面是我的xml输入
<Test>
<Head>Hey</Head>
<Message code="MNP">[Hey How are yu]
<care>test2</care>
<care>test1</care>
</Message>
</Test>
此Xml具有混合内容. 下面是我用来反序列化的类:
This Xml has mixed content. Below is classes which I used to deserialize:
@XmlRootElement(name = "Test")
public class Test {
private final String header;
private final List<Message> message;
private Test(final Builder builder) {
this.header = builder.header.orElse(null);
this.message = builder.message;
}
public static Builder builder() {
return new Builder();
}
//getters
public static final class Builder {
private Optional<String> header = Optional.empty();
private List<Message> message = List.of();
@XmlElement(name= "Head")
public Builder withHeader(final String theHeader) {
this.header = Optional.ofNullable(theHeader);
return this;
}
@XmlElement(name = "message")
public Builder withMessage(final List<Message> theMessages) {
this.message = theMessages;
return this;
}
public Test build() {
return new Test(this);
}
}
}
public class Message {
private final String code;
private final List<String> description;
private List<Object> mixedContent;
private Message(final Builder builder) {
this.code = builder.code.orElse(null);
this.description = builder.description;
}
public static Builder builder() {
return new Builder();
}
//getters
@XmlMixed
public List<Object> getHeader() {
return this.mixedContent;
}
public void setHeader(final List<Object> mixedContent) {
this.mixedContent = mixedContent;
}
@XmlTransient
public String getText() {
if (this.mixedContent == null)
return null;
final String text = this.mixedContent.stream()
.filter(obj -> obj instanceof String)
.map(String::valueOf)
.collect(Collectors.joining());
return text.trim();
}
public static final class Builder {
private Optional<String> code = Optional.empty();
private List<String> description = List.of();
private Builder() {
}
@XmlAttribute
public Builder withCode(final String theCode) {
this.code = Optional.ofNullable(theCode);
return this;
}
@XmlElement(name = "care")
public Builder withDescription(final List<String> theDescription) {
this.description =theDescription;
return this;
}
public Message build() {
return new Message(this);
}
}
}
我为混合内容值添加了setter和getter，因为我不确定如何在builder中添加它.
I have added setters and getters for mixed content value, because I am not sure how to add it in builder.
下面是我的测试代码
String input = "<Test>\n"
+ " <Head>Hey</Head>\n"
+ " <Message code=\"MNP\">[Hey How are yu]\n"
+ " <care>test2</care>\n"
+ " <care>test1</care>\n"
+ " </Message>\n"
+ "</Test>";
JAXBContext jaxbContext = JAXBContext.newInstance(Test.class);
Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
Test test = (Test) unmarshaller.unmarshal(new StringReader(input));
System.out.println(test);
如果我尝试运行此命令，则会引发异常.
If I try to run this it's throw exception.
Exception in thread "main" com.sun.xml.bind.v2.runtime.IllegalAnnotationsException: 1 counts of IllegalAnnotationExceptions
com.example.builder.Test does not have a no-arg default constructor.
this problem is related to the following location:
at com.example.builder.Test
请有人帮助我使用生成器模式进行反序列化
Please someone help me to deserialize with builder pattern
推荐答案
以下是在JAXB中使用不可变的类和构建器模式的示例.
Here is example of using immutable class and builder pattern with JAXB.
@XmlRootElement(name = "Root")
@XmlType(propOrder = {"head", "message"})
public class Root {
@XmlRootElement(name = "Root")
@XmlType(name = "RootBuilder")
public static class Builder {
private String head;
private Message.Builder message;
@XmlElement(name = "Head")
public Builder setName(String head) {
this.head = head;
return this;
}
@XmlElement(name = "Message")
public Builder setMessage(Message.Builder message) {
this.message = message;
return this;
}
public Root build() {
return new Root(this.head, this.message.build());
}
}
private final String head;
private final Message message;
Root() { // DO NOT REMOVE. This constructor is required by JAXB
throw new UnsupportedOperationException();
}
Root(String head, Message message) {
this.head = head;
this.message = message;
}
@XmlElement(name = "Head")
public String getHead() {
return this.head;
}
@XmlElement(name = "Message")
public Message getMessage() {
return this.message;
}
@Override
public String toString() {
return "Root[head=" + this.head + ", message=" + this.message + "]";
}
}
public class Message {
@XmlType(name = "MessageBuilder")
public static class Builder {
private String code;
@XmlAttribute
public Builder setCode(String code) {
this.code = code;
return this;
}
public Message build() {
return new Message(this.code);
}
}
private final String code;
Message(String code) {
this.code = code;
}
@XmlAttribute
public String getCode() {
return this.code;
}
@Override
public String toString() {
return "Message[code=" + this.code + "]";
}
}
测试
Root root1 = new Root.Builder()
.setName("Hey")
.setMessage(new Message.Builder().setCode("MNP"))
.build();
System.out.println(root1);
StringWriter stringWriter = new StringWriter();
Marshaller marshaller = JAXBContext.newInstance(Root.class).createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FRAGMENT, true);
marshaller.marshal(root1, stringWriter);
String xml = stringWriter.toString();
System.out.println(xml);
Unmarshaller unmarshaller = JAXBContext.newInstance(Root.Builder.class).createUnmarshaller();
Root.Builder rootBuilder = (Root.Builder) unmarshaller.unmarshal(new StringReader(xml));
Root root2 = rootBuilder.build();
System.out.println(root2);
输出
Root[head=Hey, message=Message[code=MNP]]
<Root><Head>Hey</Head><Message code="MNP"/></Root>
Root[head=Hey, message=Message[code=MNP]]
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