关于java:PostConstruct

@PostConstruct 是一种初始化形式

以下述代码为例

TestController中成员变量testService被@Autowired润饰
TestService将会在TestController构造方法执行后注入

@Componentpublic class TestService {    public TestService() {        System.out.println("TestService construct");    }    public void init() {        System.out.println("TestService init");    }}@RestControllerpublic class TestController {    @Autowired    private TestService testService;    public TestController() {        System.out.println("TestController construct");        testService.init();    }}

此时启动Spring利用，则会呈现报错，其起因就是testService在执行TestController构造方法时并没有实现初始化和注入；
TestController初始化时须要执行依赖中的办法时，这种写法就会引起问题；
此时就能够应用@PostConstruct来解决问题

Caused by: java.lang.NullPointerException: nullat com.example.demo.my.view.TestController.<init>(TestController.java:20) ~[classes/:na]at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:na]at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:na]at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:na]at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:490) ~[na:na]

调整代码后

@RestControllerpublic class TestController {    @Autowired    private TestService testService;    public TestController() {        System.out.println("TestController construct");    }    @PostConstruct    public void initBeforeConstruct() {        System.out.println("TestController PostConstruct");        testService.init();    }}

此时启动输入后果

从中可见总体的执行程序

构造方法
@Autowird
@PostConstruct