何时构造 Bean
要在构造 bean 时调用方法，请使用 jakarta.annotation.PostConstruct 注释：
| Java |
Groovy |
Kotlin |
import jakarta.annotation.PostConstruct; // (1)
import jakarta.inject.Singleton;
@Singleton
public class V8Engine implements Engine {
private int cylinders = 8;
private boolean initialized = false; // (2)
@Override
public String start() {
if (!initialized) {
throw new IllegalStateException("Engine not initialized!");
}
return "Starting V8";
}
@Override
public int getCylinders() {
return cylinders;
}
public boolean isInitialized() {
return initialized;
}
@PostConstruct // (3)
public void initialize() {
initialized = true;
}
}
|
import jakarta.annotation.PostConstruct // (1)
import jakarta.inject.Singleton
@Singleton
class V8Engine implements Engine {
int cylinders = 8
boolean initialized = false // (2)
@Override
String start() {
if (!initialized) {
throw new IllegalStateException("Engine not initialized!")
}
return "Starting V8"
}
@PostConstruct // (3)
void initialize() {
initialized = true
}
}
|
import jakarta.annotation.PostConstruct
import jakarta.inject.Singleton
@Singleton
class V8Engine : Engine {
override val cylinders = 8
var initialized = false
private set // (2)
override fun start(): String {
check(initialized) { "Engine not initialized!" }
return "Starting V8"
}
@PostConstruct // (3)
fun initialize() {
initialized = true
}
}
|
导入 PostConstruct 注解
定义了一个需要初始化的字段
一个方法用 @PostConstruct 注释，一旦对象被构造并完全注入就会被调用。
当 Bean 被销毁时
要在 bean 被销毁时调用方法，请使用 jakarta.annotation.PreDestroy 注释：
| Java |
Groovy |
Kotlin |
import jakarta.annotation.PreDestroy; // (1)
import jakarta.inject.Singleton;
import java.util.concurrent.atomic.AtomicBoolean;
@Singleton
public class PreDestroyBean implements AutoCloseable {
AtomicBoolean stopped = new AtomicBoolean(false);
@PreDestroy // (2)
@Override
public void close() throws Exception {
stopped.compareAndSet(false, true);
}
}
|
import jakarta.annotation.PreDestroy // (1)
import jakarta.inject.Singleton
import java.util.concurrent.atomic.AtomicBoolean
@Singleton
class PreDestroyBean implements AutoCloseable {
AtomicBoolean stopped = new AtomicBoolean(false)
@PreDestroy // (2)
@Override
void close() throws Exception {
stopped.compareAndSet(false, true)
}
}
|
import jakarta.annotation.PreDestroy // (1)
import jakarta.inject.Singleton
import java.util.concurrent.atomic.AtomicBoolean
@Singleton
class PreDestroyBean : AutoCloseable {
internal var stopped = AtomicBoolean(false)
@PreDestroy // (2)
@Throws(Exception::class)
override fun close() {
stopped.compareAndSet(false, true)
}
}
|
导入 PreDestroy 注解
一个方法用@PreDestroy 注释并且将在上下文关闭时被调用。
对于工厂 beans，Bean 注释中的 preDestroy 值告诉 Micronaut 要调用哪个方法。
| Java |
Groovy |
Kotlin |
import io.micronaut.context.annotation.Bean;
import io.micronaut.context.annotation.Factory;
import jakarta.inject.Singleton;
@Factory
public class ConnectionFactory {
@Bean(preDestroy = "stop") // (1)
@Singleton
public Connection connection() {
return new Connection();
}
}
|
import io.micronaut.context.annotation.Bean
import io.micronaut.context.annotation.Factory
import jakarta.inject.Singleton
@Factory
class ConnectionFactory {
@Bean(preDestroy = "stop") // (1)
@Singleton
Connection connection() {
new Connection()
}
}
|
import io.micronaut.context.annotation.Bean
import io.micronaut.context.annotation.Factory
import jakarta.inject.Singleton
@Factory
class ConnectionFactory {
@Bean(preDestroy = "stop") // (1)
@Singleton
fun connection(): Connection {
return Connection()
}
}
|
| Java |
Groovy |
Kotlin |
import java.util.concurrent.atomic.AtomicBoolean;
public class Connection {
AtomicBoolean stopped = new AtomicBoolean(false);
public void stop() { // (2)
stopped.compareAndSet(false, true);
}
}
|
import java.util.concurrent.atomic.AtomicBoolean
class Connection {
AtomicBoolean stopped = new AtomicBoolean(false)
void stop() { // (2)
stopped.compareAndSet(false, true)
}
}
|
import java.util.concurrent.atomic.AtomicBoolean
class Connection {
internal var stopped = AtomicBoolean(false)
fun stop() { // (2)
stopped.compareAndSet(false, true)
}
}
|
preDestroy 值在注解上设置
注解值与方法名匹配
简单地实现 Closeable 或 AutoCloseable 接口不足以使 bean 随上下文一起关闭。必须使用上述方法之一。
依赖 Bean
从属 bean 是用于构建 bean 的 bean。如果依赖 bean 的范围是 @Prototype 或未知，它将与您的实例一起被销毁。
