1. /**
    2.  * The PostConstruct annotation is used on a method that needs to be executed
    3.  * after dependency injection is done to perform any initialization. This
    4.  * method MUST be invoked before the class is put into service. This
    5.  * annotation MUST be supported on all classes that support dependency
    6.  * injection. The method annotated with PostConstruct MUST be invoked even
    7.  * if the class does not request any resources to be injected. Only one
    8.  * method can be annotated with this annotation. The method on which the
    9.  * PostConstruct annotation is applied MUST fulfill all of the following
    10.  * criteria:
    11.  * <p>
    12.  * <ul>
    13.  * <li>The method MUST NOT have any parameters except in the case of
    14.  * interceptors in which case it takes an InvocationContext object as
    15.  * defined by the Interceptors specification.</li>
    16.  * <li>The method defined on an interceptor class MUST HAVE one of the
    17.  * following signatures:
    18.  * <p>
    19.  * void &#060;METHOD&#062;(InvocationContext)
    20.  * <p>
    21.  * Object &#060;METHOD&#062;(InvocationContext) throws Exception
    22.  * <p>
    23.  * <i>Note: A PostConstruct interceptor method must not throw application
    24.  * exceptions, but it may be declared to throw checked exceptions including
    25.  * the java.lang.Exception if the same interceptor method interposes on
    26.  * business or timeout methods in addition to lifecycle events. If a
    27.  * PostConstruct interceptor method returns a value, it is ignored by
    28.  * the container.</i>
    29.  * </li>
    30.  * <li>The method defined on a non-interceptor class MUST HAVE the
    31.  * following signature:
    32.  * <p>
    33.  * void &#060;METHOD&#062;()
    34.  * </li>
    35.  * <li>The method on which PostConstruct is applied MAY be public, protected,
    36.  * package private or private.</li>
    37.  * <li>The method MUST NOT be static except for the application client.</li>
    38.  * <li>The method MAY be final.</li>
    39.  * <li>If the method throws an unchecked exception the class MUST NOT be put into
    40.  * service except in the case of EJBs where the EJB can handle exceptions and
    41.  * even recover from them.</li></ul>
    42.  * @since Common Annotations 1.0
    43.  * @see javax.annotation.PreDestroy
    44.  * @see javax.annotation.Resource
    45.  */
    46. /**
    47.  * PostConstruct注解用在需要执行的方法上
    48.  * 在完成依赖注入以执行任何初始化之后。这
    49.  * 方法必须在类投入使用之前调用。这
    50.  * 所有支持依赖的类都必须支持注解
    51.  * 注射。使用 PostConstruct 注释的方法必须被调用，甚至
    52.  * 如果类不请求注入任何资源。只有一个
    53.  * 方法可以用这个注解来注解。所采用的方法
    54.  * 应用 PostConstruct 注释必须满足以下所有条件
    55.  * 标准：
    56.  * <p>
    57.  * <ul>
    58.  * <li>方法不能有任何参数，除非是
    59.  * 拦截器，在这种情况下，它需要一个 InvocationContext 对象作为
    60.  * 由拦截器规范定义。</li>
    61.  * <li>在拦截器类上定义的方法必须具有
    62.  * 以下签名：
    63.  * <p>
    64.  * void <METHOD>(InvocationContext)
    65.  * <p>
    66.  * 对象 <METHOD>(InvocationContext) 抛出异常
    67.  * <p>
    68.  * <i>注意：PostConstruct 拦截器方法不能抛出应用程序
    69.  * 异常，但可以声明抛出检查异常，包括
    70.  * java.lang.Exception 如果相同的拦截器方法插入
    71.  * 除了生命周期事件之外的业务或超时方法。如果一个
    72.  * PostConstruct 拦截器方法返回一个值，它被忽略
    73.  * 容器。</i>
    74.  * </li>
    75.  * <li>在非拦截器类上定义的方法必须具有
    76.  * 以下签名：
    77.  * <p>
    78.  * 无效 <方法>()
    79.  * </li>
    80.  * <li>应用 PostConstruct 的方法可以是公共的、受保护的、
    81.  * 包私有或私有。</li>
    82.  * <li>除了应用程序客户端之外，该方法不得是静态的。</li>
    83.  * <li>方法可能是最终的。</li>
    84.  * <li>如果方法抛出未经检查的异常，则不得将类放入
    85.  * 服务，除了 EJB 可以处理异常的 EJB 和
    86.  * 甚至从他们身上恢复过来。</li></ul>
    87.  * @since 通用注解 1.0
    88.  * @see javax.annotation.PreDestroy
    89.  * @see javax.annotation.Resource
    90.  */
    91. @Documented
    92. @Retention (RUNTIME)
    93. @Target(METHOD)
    94. public @interface PostConstruct {
    95. }

    当一个class被注解为一个Bean，那么class上被@PostConstruct注解的方法将会在程序启动的时候执行。

    是Java自己的注解

    该注解的方法在整个Bean初始化中的执行顺序：Constructor(构造方法) -> @Autowired(依赖注入) -> @PostConstruct(注释的方法)