Configure Spring Bean XML with non-primitive type (java.nio.file.Path)

Question

I can configure Spring beans with primitive values such as String/int/long/etc. How do I get the following to work:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

    <bean class="springtest.SomeBeanTest">
        <constructor-arg index="0" type="java.nio.file.Path" value="/Users/admin/test.txt"/>
    </bean>
</beans>

UPDATE: the following works. The empty list is required for the second varargs parameter.

<bean class="springtest.SomeBeanPath">
    <constructor-arg index="0">
        <bean class="java.nio.file.Paths" factory-method="get">
            <constructor-arg index="0" value="/Users/admin/test.txt" />
            <constructor-arg index="1"><list></list></constructor-arg>
        </bean>
    </constructor-arg>
</bean>

GPI · Accepted Answer · 2014-07-21T23:27:05.007

The bean definition XML syntax can instanciate virtually any class.

You can look at the Spring documentation for a complete reference here: http://docs.spring.io/spring/docs/4.0.0.RELEASE/spring-framework-reference/htmlsingle/#beans-factory-class, out of which I extracted the following samples.

For example, you can instanciate any class with an empty constructor this way:

<bean id="exampleBean" class="examples.ExampleBean"/>

If the constructor is a static method, you can call it this way

<bean id="clientService"
class="examples.ClientService" factory-method="createInstance"/>

If you need to call a constructor with an argument, look at: http://docs.spring.io/spring/docs/4.0.0.RELEASE/spring-framework-reference/htmlsingle/#beans-constructor-injection

<bean id="foo" class="x.y.Foo">
    <constructor-arg ref="bar"/>
    <constructor-arg ref="baz"/>
</bean>

Where bar and baz should be ids of other spring beans. If instead, you use the XML attribute value, then you can use a primitive type directly. For example :

<bean id="exampleBean" class="examples.ExampleBean">
<constructor-arg name="years" value="7500000"/>
<constructor-arg name="ultimateanswer" value="42"/>
</bean>

You can also opt for calling an empty constructor first and the call setters on your beans (or mix the two methods).

<bean id="exampleBean" class="examples.ExampleBean">
<!-- setter injection using the nested <ref/> element -->
<property name="beanOne"><ref bean="anotherExampleBean"/></property>

<!-- setter injection using the neater ref attribute -->
<property name="beanTwo" ref="yetAnotherBean"/>
<property name="integerProperty" value="1"/>
</bean>

There are very advanced configuration options, allowing you to override the way Spring interprets the XML to interpret ref/value attributes. There is also a dedicated syntax for Maps, Lists, ... An expression language called Spring-EL in that you can use for dynamic evaluation at runtime inside your XML. Plus various pre/post processor options for more advanced scenarios (BeanFactoryAware, BeanFactoryPostProcessor, ...)

So, in your case, you could try to decompose like this :

<bean class="springtest.SomeBeanTest">
    <constructor-arg index="0">
        <bean class="java.nio.file.Paths" factory-method="get">
           <constructor-arg index="0" value="your path" />
           <!-- Edit: see @clay's edit to the question, the following is necessary too -->
           <constructor-arg index="1"><list></list></constructor-arg>
        </bean>
    </constructor-arg>
</bean>

Note that when there is no ambiguity, the index attribute is not necessary.

The "get" method is on j.n.f.Paths. The resulting type is j.n.f.Path with no trailing s. The example you give does not work. — clay, Jul 21 '14 at 22:56
Unfortunately, I have no Java7 to test it right now, and I do not know what your class excepts as its argument, but I am confident that the sample code is close to what you expect. The fact that I use the `Paths` (trailing s) class if because the static method `get` is on this class. This static method in turn produces a `Path` instance which I (can only) guess is the type of argument that your are expecting for your constructor... What kind of exception / error do you get ? — GPI, Jul 21 '14 at 23:19
thanks. I finally got it. I needed to add a second empty list for the vararg parameter. — clay, Jul 21 '14 at 23:24

score 0 · Answer 2 · edited May 23 '17 at 11:59

0

Pass String from configuration file and convert String into Path in SomeBeanTest class.

You can just use the Paths class:

public class SomeBeanTest(){
     public SomeBeanTest(String textPath){
         Path path = Paths.get(textPath); // String to Path
     }
}

XML:

<bean class="springtest.SomeBeanTest">
    <constructor-arg value="/Users/admin/test.txt"/>
</bean>

Note: Assuming Users/admin/test.txt is directly accessed form class-path.

Read more Create a Path from String in Java7

edited May 23 '17 at 11:59

Community

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answered Jul 21 '14 at 22:41

Braj

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Yes, but this would require that I change the underlying class to use String and not a typed Path... – clay Jul 21 '14 at 22:48

Configure Spring Bean XML with non-primitive type (java.nio.file.Path)

2 Answers2