使用 Jackson 库漂亮地打印 XML [英] Pretty printing XML with Jackson library

问题描述

我正在尝试使用 Jackson 库通过使用 JAXB 注释将 Java 对象序列化为 XML.但是，我在漂亮地打印 XML 输出时遇到了问题.

I am trying to use Jackson library to serialize Java objects into XML by using JAXB annotations. However, I face an issue in pretty-printing the XML output.

这是我的示例代码用法:

Here is my sample code usage:

ObjectMapper mapper = new XmlMapper();
mapper.enable(SerializationFeature.INDENT_OUTPUT);
String xml = mapper.writeValueAsString(person);

而且，我看到了以下异常.这里的问题是 Jackson 使用 Stax2Writer 作为 XML writer，而 Stax2 似乎不支持写入原始字符串(在这种情况下 DefaultPrettyPrinter 尝试将 " " 写入原始字符串).

And, I'm seeing the below exception. The issue here is Jackson uses Stax2Writer as XML writer and Stax2 doesn't seem to support writing raw strings (in this case DefaultPrettyPrinter tries to write " " as raw string).

    com.fasterxml.jackson.databind.JsonMappingException: Not implemented (through reference chain: xml.serialization.jackson.dto.Person["name"])
    at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:232)
    at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:197)
    at com.fasterxml.jackson.databind.ser.std.StdSerializer.wrapAndThrow(StdSerializer.java:187)
    at com.fasterxml.jackson.dataformat.xml.ser.XmlBeanSerializer.serializeFields(XmlBeanSerializer.java:174)
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152)
    at com.fasterxml.jackson.dataformat.xml.ser.XmlSerializerProvider.serializeValue(XmlSerializerProvider.java:92)
    at com.fasterxml.jackson.databind.ObjectMapper._configAndWriteValue(ObjectMapper.java:2818)
    at com.fasterxml.jackson.databind.ObjectMapper.writeValueAsString(ObjectMapper.java:2275)
    at xml.serialization.jackson.SerializationTest.main(SerializationTest.java:46)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)
Caused by: java.lang.UnsupportedOperationException: Not implemented
    at org.codehaus.stax2.ri.Stax2WriterAdapter.writeRaw(Stax2WriterAdapter.java:380)
    at org.codehaus.stax2.ri.Stax2WriterAdapter.writeRaw(Stax2WriterAdapter.java:373)
    at com.fasterxml.jackson.dataformat.xml.util.DefaultXmlPrettyPrinter$Lf2SpacesIndenter.writeIndentation(DefaultXmlPrettyPrinter.java:498)
    at com.fasterxml.jackson.dataformat.xml.util.DefaultXmlPrettyPrinter.writeLeafElement(DefaultXmlPrettyPrinter.java:271)
    at com.fasterxml.jackson.dataformat.xml.ser.ToXmlGenerator.writeString(ToXmlGenerator.java:489)
    at com.fasterxml.jackson.databind.ser.std.StringSerializer.serialize(StringSerializer.java:39)
    at com.fasterxml.jackson.databind.ser.std.StringSerializer.serialize(StringSerializer.java:21)
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:541)
    at com.fasterxml.jackson.dataformat.xml.ser.XmlBeanSerializer.serializeFields(XmlBeanSerializer.java:161)
    ... 10 more

对如何解决这个问题有任何想法吗?

Any thoughts on how to work it around?

推荐答案

根据 Stax2WriterAdapter 的文档，他们的默认实现是不完整的.代码中的注释还说 writeRaw() 方法无法使用 Java 运行时的默认设置 Stax 1.0 实现.

According to the Stax2WriterAdapter's documentation thier default implementation is incomplete. Also comments in the code say that the writeRaw() method cannot be implemented using Stax 1.0 which is default for Java runtime.

您应该按照本维基页面的建议切换到使用 Stax2 库.

在我将以下 Maven 依赖项添加到我的项目后，下面的示例开始按预期工作:

After I added the following Maven dependency to my project, the example below started to work as expected:

<dependency>
    <groupId>org.codehaus.woodstox</groupId>
    <artifactId>woodstox-core-asl</artifactId>
    <version>4.1.4</version>
</dependency>

代码示例:

public class JacksonXmlMapper {
    public static class Person {
        final public String name;

        public Person(String name) {
            this.name = name;
        }
    }

    public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper mapper = new XmlMapper();
        mapper.enable(SerializationFeature.INDENT_OUTPUT);
        System.out.println(mapper.writeValueAsString(new Person("John")));
    }
}

输出:

<Person>
   <name>John</name>
</Person>

这篇关于使用 Jackson 库漂亮地打印 XML的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！