I have an XML file that I am trying to read that has elements with attributes. I have tried from multiple examples, but the fields in my class always end up as null as shown below:
Data [type=null, value=null]
Data [type=null, value=null]
Data [type=null, value=null]
Below is the cut down example code of my issue.
Here is an example XML file located in the src/main/resources/data directory (data.xml):
<?xml version="1.0" encoding="UTF-8"?>
<list>
<data type="shopping" value="milk" />
<data type="shopping" value="eggs" />
<data type="TODO" value="return books to library" />
</list>
Below is my domain class for the XML data (Data.java):
package com.example.demo.springbatchtest.domain;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement(name = "data")
public class Data {
private final String type;
private final String value;
public Data(String type, String value) {
this.type = type;
this.value = value;
}
@XmlAttribute(name = "type")
public String getType() {
return type;
}
@XmlAttribute(name = "value")
public String getValue() {
return value;
}
@Override
public String toString() {
return "Data [type=" + type + ", value=" + value + "]";
}
}
Here is my Spring Batch job configuration file (JobConfiguration.java):
package com.example.demo.springbatchtest.configuration;
import java.util.HashMap;
import java.util.Map;
import org.springframework.batch.core.Job;
import org.springframework.batch.core.Step;
import org.springframework.batch.core.configuration.annotation.JobBuilderFactory;
import org.springframework.batch.core.configuration.annotation.StepBuilderFactory;
import org.springframework.batch.item.ItemWriter;
import org.springframework.batch.item.xml.StaxEventItemReader;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;
import org.springframework.oxm.xstream.XStreamMarshaller;
import com.example.demo.springbatchtest.domain.Data;
@Configuration
public class JobConfiguration {
@Autowired
public JobBuilderFactory jobBuilderFactory;
@Autowired
StepBuilderFactory stepBuilderFactory;
@Bean
public StaxEventItemReader<Data> dataItemReader() {
XStreamMarshaller unmarshaller = new XStreamMarshaller();
Map<String, Class> aliases = new HashMap<>();
aliases.put("data", Data.class);
unmarshaller.setAliases(aliases);
StaxEventItemReader<Data> reader = new StaxEventItemReader<>();
reader.setResource(new ClassPathResource("/data/data.xml"));
reader.setFragmentRootElementName("data");
reader.setUnmarshaller(unmarshaller);
return reader;
}
@Bean
public ItemWriter<Data> dataItemWriter() {
return items -> {
for (Data item : items) {
System.out.println(item.toString());
}
};
}
@Bean
public Step step1() {
return stepBuilderFactory.get("step1")
.<Data, Data>chunk(10)
.reader(dataItemReader())
.writer(dataItemWriter())
.build();
}
@Bean
public Job job() {
return jobBuilderFactory
.get("job")
.start(step1())
.build();
}
}
Here is my main Spring Boot class (SpringBatchTestApplication.java):
package com.example.demo.springbatchtest;
import org.springframework.batch.core.configuration.annotation.EnableBatchProcessing;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
@EnableBatchProcessing
public class SpringBatchTestApplication {
public static void main(String[] args) {
SpringApplication.run(SpringBatchTestApplication.class, args);
}
}
Here is my pom.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>SpringBatchTestSpringBoot</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>SpringBatchTestSpringBoot</name>
<description>Spring Batch Test with Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.10.RELEASE</version>
<relativePath /> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-batch</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.batch</groupId>
<artifactId>spring-batch-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-oxm</artifactId>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
It sounds like JAX-B is unable to set the Data.type and value attributes.
By default it will be looking for a getter/setter pair for each attribute, otherwise they will be treated as read-only.
The alternative would be to use field level access - @XmlAccessorType(XmlAccessType.FIELD)
Found this tutorial which helped me get the example code to work.
https://walkingtechie.blogspot.com/2017/03/spring-batch-xml-file-to-mysql-example.html
The key was to a Converter class to parse out the attributes. So in my example, I added a call set a Converter class in the dataItemReader() in the JobConfiguration class.
import com.example.demo.springbatchtest.converter.DataConverter;
...
@Autowired
private DataConverter dataConverter;
...
@Bean
public StaxEventItemReader<Data> dataItemReader() {
XStreamMarshaller unmarshaller = new XStreamMarshaller();
Map<String, Class> aliases = new HashMap<>();
aliases.put("data", Data.class);
unmarshaller.setAliases(aliases);
unmarshaller.setConverters(dataConverter); // from Walking Techie
StaxEventItemReader<Data> reader = new StaxEventItemReader<>();
reader.setResource(new ClassPathResource("/data/data.xml"));
reader.setFragmentRootElementName("data");
reader.setUnmarshaller(unmarshaller);
return reader;
}
And then I extended the Converter class to handle the attributes.
package com.example.demo.springbatchtest.converter;
import org.springframework.stereotype.Component;
import com.example.demo.springbatchtest.domain.Data;
import com.thoughtworks.xstream.converters.Converter;
import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
@Component
public class DataConverter implements Converter {
@Override
public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) {
}
@Override
public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
String type = reader.getAttribute("type");
String value = reader.getAttribute("value");
return new Data(type, value);
}
@Override
public boolean canConvert(Class type) {
return type.equals(Data.class);
}
}
The program now outputs the following:
Data [type=shopping, value=milk]
Data [type=shopping, value=eggs]
Data [type=TODO, value=return books to library]
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