春不丝豆

Question

我开始学习 spring 并想尝试一个例子。 我写了 3 个类 bellow bat 似乎我遗漏了一些东西，因为 String 没有做我打算做的事情。

package testPackage;

import org.springframework.beans.factory.annotation.*;
import org.springframework.test.context.ContextConfiguration;

@ContextConfiguration(classes=Config.class)
public class TestDrive {

    @Autowired
    private InterfaceClass obj;


    public static void main(String[] args) {

        TestDrive testDrive = new TestDrive();

        System.out.println(testDrive.obj);
        }
}

package testPackage;

import org.springframework.context.annotation.*;

public class TestClass implements InterfaceClass {

    public String test = "test string";

    @Bean
    public TestClass getTestClass() {

        TestClass testClass = new TestClass();

        return testClass;
    }

}

package testPackage;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan
public class Config {

}

当我从 main 运行此代码时，我会打印“null”。 为什么 Spring 不连接“InterfaceClass obj”？

谢谢！

Answer 1

1）在标记为@Configuration的类中声明你的Spring Beans

2) 在main函数中，使用 ApplicationContext 来获取 TestDrive 对象。 切勿将 Spring bean 对象与从 new 运算符创建的对象混合使用

试驾课程

public class TestDrive {

    @Autowired
    private InterfaceClass obj;

    @Autowired
    private ApplicationContext appContext;

    public static void main(String[] args) {
        //you will have to use this method, to get bean of TestDrive
        // You should not use new operator, not advisable to mix new operator with spring beans
        ApplicationContext context = new AnnotationConfigApplicationContext(Config.class);
        TestDrive drive = context.getBean(TestDrive.class);

        System.out.println(drive.getString());

    }

    public String getString(){
        String str = obj.getTestString();
        return str;
    }
}

测试类

public class TestClass implements InterfaceClass{
    public String test = "test string";
    public String getTestString(){
        return test;
    }

}

接口类

public interface InterfaceClass {
    public String getTestString();
}

配置

@Configuration
public class Config {

    @Bean
    public InterfaceClass getTestClass() {
        TestClass testClass = new TestClass();
        return testClass;
    }

    @Bean
    public TestDrive getTestDrive(){
        return  new TestDrive();
    }
}   

Answer 2

将@Configuration注释放在测试类的顶部：-

package testPackage;

import org.springframework.context.annotation.*;

@Configuration
public class TestClass implements InterfaceClass {

    public String test = "test string";

    @Bean
    public TestClass getTestClass() {

        TestClass testClass = new TestClass();

        return testClass;
    }

}