Datasheet

log4j.rootLogger=FATAL, first

log4j.appender.first=org.apache.log4j.ConsoleAppender

log4j.appender.first.layout=org.apache.log4j.PatternLayout

log4j.appender.first.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n

Wiring Beans Automatically by Type

In the preceding example you wired the properties of the CalculateSpring bean explicitly. In practice,

you can actually ask the Spring container to automatically wire up the properties. The next “Try It Out”

shows how to perform automatic wiring.

Try It Out Autowire by Type

Automatic wiring can save you some work when you’re creating context descriptors. Basically, when

you tell the Spring container to autowire, you’re asking it to find the beans that fit together. This can

be done automatically by the container without you providing explicit instructions on how to wire the

beans together. There are many different ways to autowire, including by name, by type, using the con-

structor, or using Spring’s autodetection. Each of these will be described in a bit. For now, let’s discuss

the most popular type of autowiring, autowiring by type.

Autowiring by type means that the container should try to wire beans together by matching the required

Java class and/or Java interface. For example, a

CalculateSpring object can be wired with an instance

Operation (Java interface) type, and an instance of ResultWriter (Java interface) type. When told to

autowire by type, the Spring container searches the context descriptor for a component that implements

the

Operation interface, and for a component that implements the ResultWriter interface.

This feature can be a time-saver if you are creating a large number of beans in a context descriptor.

To try out autowiring by type with the

CalculateSpring project, follow these steps:

1. Change the directory to the src/springfirst/target/classes directory:

cd src/chapter1/springfirst/target/classes

2. You should see beans.xml here. Maven 2 has copied the context descriptor here during compi-

lation. Modify the

beans.xml context descriptor, as shown in the following listing; the changed

lines are highlighted. Note that you need to remove the lines not shown in the listing.

<?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-2.0.xsd”>

</beans>

Chapter 1: Jump Start Spring 2

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