4
我想知道如何初始化Spring Bean中的字段？下面是幾個可能的解決方案：在Spring Beans中初始化字段的正確方法是什麼？
1.初始化場直接申報
import org.springframework.stereotype.Component;
@Component
public class DeclarationInit {
private final int field = Integer.MAX_VALUE;
public int getField() {
return field;
}
}
2.初始化領域使用@Value註釋
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component
public class ValueInit {
@Value("#{T(Integer).MAX_VALUE}")
private int field;
public int getField() {
return field;
}
}
3.使用@Autowired註釋初始化場
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
@Component
public class AutowiredInit {
private int field;
@Autowired
private void initField() {
field = Integer.MAX_VALUE;
}
public int getField() {
return field;
}
}
使用@PostConstruct註釋
import javax.annotation.PostConstruct;
import org.springframework.stereotype.Component;
@Component
public class PostConstructInit {
private int field;
@PostConstruct
private void initField() {
field = Integer.MAX_VALUE;
}
public int getField() {
return field;
}
}
所有測試成功，並且沒有顯示出任何區別4.初始化字段：
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.equalTo;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.SpringApplicationConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = SomeTestContextConfiguration.class)
public class FieldInitTest {
@Autowired
private DeclarationInit declarationInit;
@Autowired
private ValueInit valueInit;
@Autowired
private AutowiredInit autowiredInit;
@Autowired
private PostConstructInit postConstructInit;
@Test
public void shouldInitializeFieldOnDeclaration() {
assertThat(declarationInit.getField(), equalTo(Integer.MAX_VALUE));
}
@Test
public void shouldInitializeFieldWithValueAnnotation() {
assertThat(valueInit.getField(), equalTo(Integer.MAX_VALUE));
}
@Test
public void shouldInitializeFieldWithAutowiredSetter() {
assertThat(autowiredInit.getField(), equalTo(Integer.MAX_VALUE));
}
@Test
public void shouldInitializeFieldWithPostConstruct() {
assertThat(postConstructInit.getField(), equalTo(Integer.MAX_VALUE));
}
}
此聲明彼此相等，或者我應該使用只有他們中的一個或兩個都沒有？