Geronimo XBean

1 Overview
    XBean是Apache Geronimo的子项目，目标是像Eclipse IDE那样，用于创建基于插件的服务器（跟Geronimo GBean的目标有些重合）。从现状来看，XBean更多地被用于简化Spring 配置。例如，Apache ActiveMQ的配置基于XBean。

2 Custom namespace
    最简单的custom namespace是java://加上全路径包名的形式，以下是个简单的例子：

package com.versus.misc.xbean;

import java.math.BigDecimal;

import org.apache.commons.lang.builder.ToStringBuilder;
import org.apache.commons.lang.builder.ToStringStyle;

public class Product {
	private String name;
	private BigDecimal price;

	public String toString() {
		return new ToStringBuilder(this, ToStringStyle.SHORT_PREFIX_STYLE)
		.append("name", name)
		.append("price", price).toString();
	}
	
	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public BigDecimal getPrice() {
		return price;
	}

	public void setPrice(BigDecimal price) {
		this.price = price;
	}
}

    以下是配置文件xbean.xml的内容：

<beans xmlns:p="java://com.versus.misc.xbean">
  <p:Product id="product" name="USD/JPY" price="100.00"/>
</beans>

    以下是测试用的test case：

package com.versus.misc.xbean;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;

import java.math.BigDecimal;

import org.apache.xbean.spring.context.ClassPathXmlApplicationContext;
import org.junit.Test;

public class XBeanTest {

	@Test
	public void test() {
		ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:com/versus/misc/xbean/xbean.xml");
		Product product = (Product)context.getBean("product");
		assertNotNull(product);
		assertEquals("USD/JPY", product.getName());
		assertEquals(new BigDecimal("100.00"), product.getPrice());
	}
}

    以上的例子中，custom namespace是java://com.versus.misc.xbean；Product是定义在com.versus.misc.xbean包中的一个类；Product类的成员变量都被映射成XML的属性。需要注意的是，必须使用org.xbean.spring.context.ClassPathXmlApplicationContext，而不是Spring自带的ApplicationContext。

 

3 Custom mapping
    在之前的例子中，如果给Product类增加一个名为id的int型成员变量，那么为了避免和标准Spring属性的冲突，应该使用custom mapping。首先要在META-INF/services/org/apache/xbean/spring/目录下建立一个名为$namespace的属性文件。例如，如果namespace是http://xbean.versus.com/product，那么需要建立META-INF/services/org/apache/xbean/spring/http/xbean.versus.com/product文件，其内容如下：

package = com.versus.misc.xbean
product = com.versus.misc.xbean.Product
product.alias.productId = id #将id成员变量映射为productId属性

    以下是配置文件xbean.xml的内容：

<beans xmlns:p="http://xbean.versus.com/product" >
  <p:product id="product" productId="1" name="USD/JPY" price="100.00"/>
</beans>

    以下是测试用的test case：

package com.versus.misc.xbean;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;

import java.math.BigDecimal;

import org.apache.xbean.spring.context.ClassPathXmlApplicationContext;
import org.junit.Test;

public class XBeanTest {

	@Test
	public void test() {
		ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:com/versus/misc/xbean/xbean.xml");
		Product product = (Product)context.getBean("product");
		assertNotNull(product);
		assertEquals(1, product.getId());
		assertEquals("USD/JPY", product.getName());
		assertEquals(new BigDecimal("100.00"), product.getPrice());
	}
}

 

4 Constructor injection
    除了setter注入之外，XBean也支持constructor注入，以下是个简单的例子：

package com.versus.misc.xbean;

import java.math.BigDecimal;

import org.apache.commons.lang.builder.ToStringBuilder;
import org.apache.commons.lang.builder.ToStringStyle;

public class Product {
	private int id;
	private String name;
	private BigDecimal price;
	private Leverage leverage;

	public String toString() {
		return new ToStringBuilder(this, ToStringStyle.SHORT_PREFIX_STYLE)
		.append("id", id)
		.append("name", name)
		.append("price", price)
		.append("leverage", leverage).toString();
	}
	
	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}
	
	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public BigDecimal getPrice() {
		return price;
	}

	public void setPrice(BigDecimal price) {
		this.price = price;
	}

	public Leverage getLeverage() {
		return leverage;
	}

	public void setLeverage(Leverage leverage) {
		this.leverage = leverage;
	}
}

 

package com.versus.misc.xbean;

import java.math.BigDecimal;

public class Leverage {
	private int value;
	private BigDecimal margin;
	
	public Leverage(int value, BigDecimal margin) {
		this.value = value;
		this.margin = margin;
	}
	
	public int getValue() {
		return value;
	}
	
	public BigDecimal getMargin() {
		return margin;
	}
}

    META-INF/services/org/apache/xbean/spring/http/xbean.versus.com/product文件的内容如下:

package = com.versus.misc.xbean
product = com.versus.misc.xbean.Product
leverage = com.versus.misc.xbean.Leverage
product.alias.productId = id
com.versus.misc.xbean.Leverage(int,java.math.BigDecimal).parameterNames=value margin

    以下是配置文件xbean.xml的内容：

<beans xmlns:p="http://xbean.versus.com/product">
  <p:product id="product" productId="1" name="##USD/JPY" price="100.00" leverage="#leverage"/>
  <p:leverage id="leverage" value="50" margin="12345"/>
</beans>

    以下是测试用的test case：

package com.versus.misc.xbean;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;

import java.math.BigDecimal;

import org.apache.xbean.spring.context.ClassPathXmlApplicationContext;
import org.junit.Test;

public class XBeanTest {

	@Test
	public void test() {
		ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:com/versus/misc/xbean/xbean.xml");
		
		Product product = (Product)context.getBean("product");
		assertNotNull(product);
		assertEquals(1, product.getId());
		assertEquals("#USD/JPY", product.getName());
		assertEquals(new BigDecimal("100.00"), product.getPrice());
		
		Leverage leverage = (Leverage)context.getBean("leverage");
		assertNotNull(leverage);
		assertEquals(50, leverage.getValue());
		assertEquals(new BigDecimal("12345"), leverage.getMargin());
		
		assertEquals(leverage, product.getLeverage());
	}
}

    需要注意的是，以上例子中p:product的leverage属性通过#引用了leverage。如果你期望配置一个以#开头的字符串，那么字符串的需要以##开头（例如以上例子中，product中name成员变量的值是#USD/JPY）。

 

5 Assembling collections
    跟Spring一样，XBean也支持装配集合类型。以上的例子中，假设每种FX交易的商品可以有多个杠杆，那么需要进行以下的修改：

package com.versus.misc.xbean;

import java.math.BigDecimal;
import java.util.List;

import org.apache.commons.lang.builder.ToStringBuilder;
import org.apache.commons.lang.builder.ToStringStyle;

public class Product {
	private int id;
	private String name;
	private BigDecimal price;
	private List<Leverage> leverages;

	public String toString() {
		return new ToStringBuilder(this, ToStringStyle.SHORT_PREFIX_STYLE)
		.append("id", id)
		.append("name", name)
		.append("price", price)
		.append("leverages", leverages).toString();
	}
	
	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}
	
	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public BigDecimal getPrice() {
		return price;
	}

	public void setPrice(BigDecimal price) {
		this.price = price;
	}

	public List<Leverage> getLeverages() {
		return leverages;
	}

	public void setLeverages(List<Leverage> leverages) {
		this.leverages = leverages;
	}
}

    META-INF/services/org/apache/xbean/spring/http/xbean.versus.com/product文件的内容如下:

package = com.versus.misc.xbean
product = com.versus.misc.xbean.Product
leverage = com.versus.misc.xbean.Leverage
product.alias.productId = id
product.alias.leverages.list = leverages
com.versus.misc.xbean.Leverage(int,java.math.BigDecimal).parameterNames=value margin

    以下是配置文件xbean.xml的内容：

<beans xmlns:p="http://xbean.versus.com/product">
  <p:product id="product" productId="1" name="USD/JPY" price="100.00">
      <leverages>
          <p:leverage id="leverage1" value="50" margin="12345"/>
          <p:leverage id="leverage2" value="100" margin="24690"/>
      </leverages>
  </p:product>
</beans>

    以下是测试用的test case：

package com.versus.misc.xbean;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;

import java.math.BigDecimal;

import org.apache.xbean.spring.context.ClassPathXmlApplicationContext;
import org.junit.Test;

public class XBeanTest {

	@Test
	public void test() {
		ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:com/versus/misc/xbean/xbean.xml");
		
		Product product = (Product)context.getBean("product");
		assertNotNull(product);
		assertEquals(1, product.getId());
		assertEquals("USD/JPY", product.getName());
		assertEquals(new BigDecimal("100.00"), product.getPrice());
		assertEquals(2, product.getLeverages().size());
		
		Leverage leverage1 = product.getLeverages().get(0);
		assertNotNull(leverage1);
		assertEquals(50, leverage1.getValue());
		assertEquals(new BigDecimal("12345"), leverage1.getMargin());
		
		Leverage leverage2 = product.getLeverages().get(1);
		assertNotNull(leverage2);
		assertEquals(100, leverage2.getValue());
		assertEquals(new BigDecimal("24690"), leverage2.getMargin());
	}
}