Spring

Injection Types

Constructor Type Injection

public class Subclass implements Super {
  private String fHost = null;
  private int fPort = 0;

  public Subclass(String fHost, int fPort) {
    this.fHost = fHost;
    this.fPort = fPort;
  }

  @Override
  public String read() {
    // your impl goes here
    return null;
  }
}
                

The fHost and fPort arguments are then wired using constructor-arg attributes defined in the XML config file:

 name="reader" class="com.test.Subclass">
   value="test.com" />
   value="1040" />
 

You can set references to other beans, too via the constructor arguments.

 name="readerService" 
    class="com.test.ReaderService">
   ref="reader" />


 name="reader" class="com.test.Subclass">
   value="src/main/resources/basics/basics-trades-data.txt" />
 

This is how the ReaderService will look with a constructor accepting an IReader type:
public class ReaderService  
{
 private IReader reader = null;
 public ReaderService(IReader reader)  {
this.reader = reader;  
}  
... }

 Argument type resolution

 name="reader" class="com.test.Subclass">
   type="String" value="test.com" />
   type="int" value="1040" />

                

The types are normal Java types—such as int, boolean, double, String, and so on.
You could also set index’s on the values, starting the index from zero as shown here:

 name="reader"  class="com.test.Subclass">
   index="0" type="String" value="test.com" />
   index="1" type="int" value="1040" />

Setter Type Injection

In order to use the setter injection, we have to provide setters on the respective variables. If the property exhibits read and write characteristics, provide both a setter and a getter on the variable.

public class ReaderService {
  private IReader reader = null;

  // Setter and getter
  public void setReader(IReader reader) {
    this.reader = reader;
  }
  
  public IReader getReader() {
    return reader;
  }
  ...
}            

The significant points are the the setter and getter methods on the IReader variable and the omission of the constructor altogether. The configuration of the class in our XML file looks like this:

 name="readerService" 
    class="com.test.ReaderService">
  
   name="reader" ref="reader"/>


 name="reader" class="com.test.Subclass">
  ...
 

We can mix the injection types as we like .

 name="reader" 
    class="........">
   value="src/main/resources/basics/basics-trades-data.txt" />
   name="componentName" value="TradeFileReader"/>