如何从该配置文件获取属性到另一个Java类？

Question

I was able to extract the properties from an application.properties file. But I was unable to use it in another class.

ConfigFile

package com.springweb.springApplication.config;    
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;    

@Component
public class AppConfig {

private final String App;    
private final String servers;    

@Autowired
public AppConfig(@Value("${Application}") String App,
                @Value("${APP_SERVERS}") String servers) {
    this.App = App;
    this.servers = servers;

    System.out.println("================ " + servers + "================ ");
}    

public String getApp() {
    return App;
}

public String getServers() {
    return servers;
}

}

Class code SNippet

public class MyFirstClass{

private String RED = "RED";
private String GREEN = "GREEN";
private String YELLOW = "YELLOW";   


public List<ModelSet> findall() {


    Properties prop = new Properties();
    InputStream input = null;

            try {
                input = new
                FileInputStream("C:/Users/Jackie/workspace/springApplication/lib/myConfig.properties");
                prop.load(input);
            } catch (FileNotFoundException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }                           


        String servers = prop.getProperty("APP_SERVERS");
        String Application = prop.getProperty("Application");
}

I want to replace inputSteam and use the properties file internally. Instead of having stream to find the file. I want to get those variables from the config file. I tried looking at http://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-external-config.html but I could not find how to call the variables into another class. I only have a slightest clue on how to apporach this. Right now I believe I have to do something like .getproperty or env properties.

Answer 1

Inject AppConfig into the MyFirstClass class.

Edit: I may not understand what you are asking.

Here is option 1 of what I think you want: Summarized as "I injected stuff into AppConfig and want to reference that injected stuff in MyFirstClas".

1. Keep the configuration for the AppConfig class.
2. Add an @Inject (or @Autowired) member of type AppConfig to the MyFirstClass class.
3. Call the AppConfig getters to retrieve the config values.

Here is option 2 of what I think you want: Summarized as "I injected properties in some class and want to inject more properties in some other class"

1. Create a PropertyPlaceholderConfigurer in your Spring configuration (search for PropertyPlaceholderConfigurer in the Spring Reference or on google)
2. Inject the properties into your "some other class" using configuration similar to this: <property name="memberNameInYourClass" value="${propertyName.from.properties.file}"/>

Answer 2

I was able to extract the properties from an application.properties file. But I was unable to use it in another class.

You was not able to get properties in MyFirstClass with @Value because MyFirstClass is not a Spring component so @Value was ignored.

Annotate MyFirstClass as Spring Component and Inject properties with @Value should solve the issue

Update : Injection is done after the constructor is called

@Component
public class MyFirstClass{

    private String app;

    private String servers;

    @Autowired
    public MyFirstClass(@Value("${Application}") String App,
            @Value("${APP_SERVERS}") String servers) {
        this.App = App;
        this.servers = servers;

        System.out.println("================ " + servers + "================ ");
    } 

    private String RED = "RED";
    private String GREEN = "GREEN";
    private String YELLOW = "YELLOW";   


    public List<ModelSet> findall() {
        // process findall Spring will resolve properties for you!
    }
}

Answer 3

You can get the properties by injecting Environment to the class.

public class MyFirstClass{

@Autowired
private Environment env;

private String RED = "RED";
private String GREEN = "GREEN";
private String YELLOW = "YELLOW";   


public List<ModelSet> findall() {


Properties prop = new Properties();
InputStream input = null;

        try {
            input = new
            FileInputStream(env.getProperty("a.b.c.path"));
            prop.load(input);
        } catch (FileNotFoundException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }                           


    String servers = prop.getProperty("APP_SERVERS");
    String Application = prop.getProperty("Application");
}

in your application.properties file, define the path like

a.b.c.path = /home/jackie/asd

Answer 4

Class

@Component
public class MyFirstClass{


@Value("${Application}")
private String Application;
@Value("${APP_SERVERS}")
private String servers; 


private String RED = "RED";
private String GREEN = "GREEN";
private String YELLOW = "YELLOW";   


@PostConstruct
public List<ModelSet> findall() {

//normal code that called the properties variables will be read automatically.
System.out.println(Application + "this is application from properties");
}

Output

Hellosir this is application from properties

Application.properties

Application = Hellosir
Servers = server1,server2,server3

This worked for me and what I needed. I added @Component above the class, and added @PostConstruct below. Now it will print the properties value.