XML Examples

Tip

View the complete source: examples/xml_processing.rs

This page provides comprehensive examples for working with XML files using Spring Batch RS.

Setup

Add the XML feature to your Cargo.toml:

[dependencies]
spring-batch-rs = { version = "0.1", features = ["xml"] }
serde = { version = "1.0", features = ["derive"] }

---

Basic XML Reading

Reading Elements by Tag

use spring_batch_rs::{
    core::{step::StepBuilder, item::PassThroughProcessor},
    item::xml::XmlItemReaderBuilder,
    item::logger::LoggerWriter,
};
use serde::{Deserialize, Serialize};

#[derive(Debug, Deserialize, Serialize, Clone)]
#[serde(rename = "book")]
struct Book {
    #[serde(rename = "@id")]
    id: String,
    title: String,
    author: String,
    year: i32,
    price: f64,
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let reader = XmlItemReaderBuilder::<Book>::new()
        .tag("book")  // Extract <book> elements
        .capacity(1024)
        .from_path("books.xml")?;

    let writer = LoggerWriterBuilder::<Vehicle>::new().build();
    let processor = PassThroughProcessor::<Book>::new();

    let step = StepBuilder::new("read-xml")
        .chunk::<Book, Book>(10)
        .reader(&reader)
        .processor(&processor)
        .writer(&writer)
        .build();

    let mut execution = spring_batch_rs::core::step::StepExecution::new("read-xml");
    step.execute(&mut execution)?;

    Ok(())
}

Input file (books.xml):

<?xml version="1.0" encoding="UTF-8"?>
<books>
  <book id="1">
    <title>The Rust Programming Language</title>
    <author>Steve Klabnik</author>
    <year>2018</year>
    <price>39.99</price>
  </book>
  <book id="2">
    <title>Programming Rust</title>
    <author>Jim Blandy</author>
    <year>2021</year>
    <price>49.99</price>
  </book>
</books>

Tip

Use #[serde(rename = "@field")] for XML attributes and #[serde(rename = "$value")] for text content.

---

XML Attributes

Reading Attributes and Elements

#[derive(Debug, Deserialize, Serialize, Clone)]
#[serde(rename = "vehicle")]
struct Vehicle {
    #[serde(rename = "@type")]
    vehicle_type: String,
    #[serde(rename = "@id")]
    id: String,
    make: String,
    model: String,
    year: i32,
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let reader = XmlItemReaderBuilder::<Vehicle>::new()
        .tag("vehicle")
        .from_path("vehicles.xml")?;

    Ok(())
}

Input:

<?xml version="1.0" encoding="UTF-8"?>
<vehicles>
  <vehicle type="car" id="v1">
    <make>Toyota</make>
    <model>Camry</model>
    <year>2023</year>
  </vehicle>
  <vehicle type="truck" id="v2">
    <make>Ford</make>
    <model>F-150</model>
    <year>2024</year>
  </vehicle>
</vehicles>

---

Complex Nested Structures

Nested Objects and Arrays

#[derive(Debug, Deserialize, Serialize, Clone)]
struct Displacement {
    #[serde(rename = "@unit")]
    unit: String,
    #[serde(rename = "$value")]
    value: String,
}

#[derive(Debug, Deserialize, Serialize, Clone)]
#[serde(rename_all = "camelCase")]
struct Engine {
    #[serde(rename = "@cylinders")]
    cylinders: i32,
    #[serde(rename = "type")]
    engine_type: String,
    displacement: Displacement,
}

#[derive(Debug, Deserialize, Serialize, Clone)]
#[serde(rename_all = "camelCase")]
struct Features {
    #[serde(rename = "feature", default)]
    items: Vec<String>,
}

#[derive(Debug, Deserialize, Serialize, Clone)]
#[serde(rename = "vehicle")]
#[serde(rename_all = "camelCase")]
struct ComplexVehicle {
    #[serde(rename = "@type")]
    vehicle_type: String,
    #[serde(rename = "@id")]
    id: String,
    make: String,
    model: String,
    year: i32,
    engine: Engine,
    features: Features,
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let reader = XmlItemReaderBuilder::<ComplexVehicle>::new()
        .tag("vehicle")
        .capacity(2048)
        .from_path("complex_vehicles.xml")?;

    Ok(())
}

Input:

<?xml version="1.0" encoding="UTF-8"?>
<vehicles>
  <vehicle type="car" id="1">
    <make>Toyota</make>
    <model>Camry</model>
    <year>2023</year>
    <engine cylinders="4">
      <type>Inline</type>
      <displacement unit="L">2.5</displacement>
    </engine>
    <features>
      <feature>Bluetooth</feature>
      <feature>Backup Camera</feature>
      <feature>Lane Assist</feature>
    </features>
  </vehicle>
</vehicles>

---

Basic XML Writing

Writing XML Documents

use spring_batch_rs::item::xml::XmlItemWriterBuilder;

#[derive(Serialize)]
#[serde(rename = "product")]
struct Product {
    #[serde(rename = "@id")]
    id: u32,
    name: String,
    price: f64,
    category: String,
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let writer = XmlItemWriterBuilder::new()
        .root_tag("products")
        .item_tag("product")
        .from_path("output.xml")?;

    Ok(())
}

Output:

<?xml version="1.0" encoding="UTF-8"?>
<products>
  <product id="1">
    <name>Laptop</name>
    <price>999.99</price>
    <category>Electronics</category>
  </product>
  <product id="2">
    <name>Mouse</name>
    <price>29.99</price>
    <category>Electronics</category>
  </product>
</products>

---

XML to JSON Transformation

Convert XML to JSON format:

use spring_batch_rs::{
    core::{job::JobBuilder, step::StepBuilder, item::PassThroughProcessor},
    item::{
        xml::XmlItemReaderBuilder,
        json::JsonItemWriterBuilder,
    },
};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let reader = XmlItemReaderBuilder::<Vehicle>::new()
        .tag("vehicle")
        .from_path("vehicles.xml")?;

    let writer = JsonItemWriterBuilder::<Vehicle>::new()
        .pretty_formatter(true)
        .from_path("vehicles.json")?;

    let processor = PassThroughProcessor::<Vehicle>::new();

    let step = StepBuilder::new("xml-to-json")
        .chunk::<Vehicle, Vehicle>(50)
        .reader(&reader)
        .processor(&processor)
        .writer(&writer)
        .build();

    let job = JobBuilder::new().start(&step).build();
    job.run()?;

    Ok(())
}

---

CSV to XML Transformation

Convert CSV to XML format:

use spring_batch_rs::{
    item::csv::CsvItemReaderBuilder,
    core::item::PassThroughProcessor,
};
use serde::{Deserialize, Serialize};

#[derive(Debug, Clone, Deserialize, Serialize)]
#[serde(rename = "employee")]
struct Employee {
    #[serde(rename = "@id")]
    id: u32,
    first_name: String,
    last_name: String,
    department: String,
    salary: f64,
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let reader = CsvItemReaderBuilder::<Employee>::new()
        .has_headers(true)
        .from_path("employees.csv")?;

    let writer = XmlItemWriterBuilder::new()
        .root_tag("employees")
        .item_tag("employee")
        .from_path("employees.xml")?;

    let processor = PassThroughProcessor::<Employee>::new();

    let step = StepBuilder::new("csv-to-xml")
        .chunk::<Employee, Employee>(100)
        .reader(&reader)
        .processor(&processor)
        .writer(&writer)
        .build();

    let job = JobBuilder::new().start(&step).build();
    job.run()?;

    Ok(())
}

---

XML Processing with Transformation

Data Enrichment

use spring_batch_rs::core::item::{ItemProcessor, ItemProcessorResult};
use std::collections::HashMap;

#[derive(Deserialize, Clone)]
#[serde(rename = "order")]
struct OrderInput {
    #[serde(rename = "@id")]
    order_id: String,
    product_id: u32,
    quantity: u32,
}

#[derive(Serialize)]
#[serde(rename = "enriched_order")]
struct EnrichedOrder {
    #[serde(rename = "@id")]
    order_id: String,
    product_id: u32,
    product_name: String,
    quantity: u32,
    unit_price: f64,
    total: f64,
}

struct OrderEnricher {
    catalog: HashMap<u32, (String, f64)>,
}

impl ItemProcessor<OrderInput, EnrichedOrder> for OrderEnricher {
    fn process(&self, item: &OrderInput) -> ItemProcessorResult<EnrichedOrder> {
        let (product_name, unit_price) = self.catalog
            .get(&item.product_id)
            .cloned()
            .ok_or_else(|| spring_batch_rs::error::BatchError::ItemProcessor(
                format!("Unknown product: {}", item.product_id)
            ))?;

        let total = unit_price * item.quantity as f64;

        Ok(EnrichedOrder {
            order_id: item.order_id.clone(),
            product_id: item.product_id,
            product_name,
            quantity: item.quantity,
            unit_price,
            total,
        })
    }
}

---

Validation and Filtering

Validate XML Data

#[derive(Deserialize, Clone)]
#[serde(rename = "record")]
struct RawRecord {
    #[serde(rename = "@id")]
    id: String,
    value: String,
    status: String,
}

#[derive(Serialize)]
#[serde(rename = "validated_record")]
struct ValidatedRecord {
    #[serde(rename = "@id")]
    id: u32,
    value: f64,
    status: String,
}

struct RecordValidator;

impl ItemProcessor<RawRecord, ValidatedRecord> for RecordValidator {
    fn process(&self, item: &RawRecord) -> ItemProcessorResult<ValidatedRecord> {
        // Validate ID
        let id = item.id.parse::<u32>()
            .map_err(|_| spring_batch_rs::error::BatchError::ItemProcessor(
                format!("Invalid ID: {}", item.id)
            ))?;

        // Validate value
        let value = item.value.parse::<f64>()
            .map_err(|_| spring_batch_rs::error::BatchError::ItemProcessor(
                format!("Invalid value: {}", item.value)
            ))?;

        // Validate status
        if !["active", "pending", "completed"].contains(&item.status.as_str()) {
            return Err(spring_batch_rs::error::BatchError::ItemProcessor(
                format!("Invalid status: {}", item.status)
            ));
        }

        Ok(ValidatedRecord {
            id,
            value,
            status: item.status.clone(),
        })
    }
}

---

CDATA and Special Characters

Handling CDATA Sections

#[derive(Debug, Deserialize, Serialize, Clone)]
#[serde(rename = "article")]
struct Article {
    #[serde(rename = "@id")]
    id: String,
    title: String,
    #[serde(rename = "$value")]
    content: String,  // Can contain CDATA
}

Input:

<?xml version="1.0" encoding="UTF-8"?>
<articles>
  <article id="1">
    <title>Sample Article</title>
    <content><![CDATA[
      This content can contain <special> characters & symbols.
      Line breaks are preserved.
    ]]></content>
  </article>
</articles>

---

Real-World Example: RSS Feed Processing

Process RSS-like feed format:

#[derive(Debug, Deserialize, Serialize, Clone)]
#[serde(rename = "item")]
struct FeedItem {
    title: String,
    link: String,
    description: String,
    #[serde(rename = "pubDate")]
    pub_date: String,
    category: String,
}

#[derive(Serialize)]
struct ProcessedFeedItem {
    title: String,
    url: String,
    summary: String,
    published: String,
    tags: Vec<String>,
}

struct FeedProcessor;

impl ItemProcessor<FeedItem, ProcessedFeedItem> for FeedProcessor {
    fn process(&self, item: &FeedItem) -> ItemProcessorResult<ProcessedFeedItem> {
        // Clean HTML from description
        let summary = item.description
            .replace("<p>", "")
            .replace("</p>", "")
            .replace("<br>", " ");

        // Parse categories into tags
        let tags: Vec<String> = item.category
            .split(',')
            .map(|s| s.trim().to_string())
            .collect();

        Ok(ProcessedFeedItem {
            title: item.title.clone(),
            url: item.link.clone(),
            summary,
            published: item.pub_date.clone(),
            tags,
        })
    }
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let reader = XmlItemReaderBuilder::<FeedItem>::new()
        .tag("item")
        .capacity(2048)
        .from_path("feed.xml")?;

    let processor = FeedProcessor;

    let writer = JsonItemWriterBuilder::<Vehicle>::new()
        .pretty_formatter(true)
        .from_path("processed_feed.json")?;

    let step = StepBuilder::new("process-feed")
        .chunk::<FeedItem, ProcessedFeedItem>(50)
        .reader(&reader)
        .processor(&processor)
        .writer(&writer)
        .build();

    let job = JobBuilder::new().start(&step).build();
    job.run()?;

    Ok(())
}

---

Common Patterns

Text Content with Attributes

#[derive(Deserialize, Serialize, Clone)]
struct Price {
    #[serde(rename = "@currency")]
    currency: String,
    #[serde(rename = "$value")]
    amount: f64,
}

XML:

<price currency="USD">99.99</price>

Optional Elements

#[derive(Deserialize, Serialize, Clone)]
#[serde(rename = "product")]
struct Product {
    name: String,
    #[serde(default)]
    description: Option<String>,
    price: f64,
}

Default Values

#[derive(Deserialize, Serialize, Clone)]
struct Config {
    #[serde(default = "default_timeout")]
    timeout: u32,
}

fn default_timeout() -> u32 {
    30
}

---

Performance Tips

Buffer Size

Increase capacity() for documents with large elements (default: 8192 bytes)

Tag Selection

Choose specific tag names to extract only needed elements

Memory Usage

XML parsing is streaming - memory usage is proportional to element size, not file size

Chunk Size

Use moderate chunk sizes (50-100) for XML due to parsing overhead

Troubleshooting

Caution

Common Issues:

1. Attribute not found: Add #[serde(rename = "@field")] for XML attributes
2. Text content missing: Use #[serde(rename = "$value")] for element text
3. Parsing errors: Check XML is well-formed and matches struct definition
4. Buffer overflow: Increase capacity() for large elements

Next Steps

• JSON Examples - Process JSON files
• Database Examples - Read/write databases
• API Reference - Complete API documentation