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批注将Java对象序列化为XML.但是，我在漂亮地打印XML输出时遇到了一个问题.

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，杰克逊使用Stax2Writer作为XML编写器，而Stax2似乎不支持编写原始字符串(在这种情况下，DefaultPrettyPrinter尝试将"\ n"编写为原始字符串).

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 "\n" 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

关于如何解决它的任何想法?

Any thoughts on how to work it around?

推荐答案

根据Stax2WriterAdapter的文档，其默认实现不完整.代码中的注释还指出，不能使用Stax 1.0来实现writeRaw()方法，Stax 1.0是Java运行时的默认设置.

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.

您应按照此Wiki页面上的建议切换使用Stax2库.

在我的项目中添加以下Maven依赖项之后，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！