spring注解使用

spring的常用注解：

bean定义

public class MyBean {
}

/**
 * bean注入
 * {@link MyBean}
 */
@Configuration
public class MyConfig {
    @Bean
    public MyBean getMyBean(){
        return new MyBean();
    }
    @Bean("bean2")
    public MyBean myBean2(){
        return new MyBean();
    }
}

测试

@SpringBootApplication(scanBasePackages = "com.anocation.beanConfig")
@RestController
public class BeanApp{
    public static void main(String[] args){
        SpringApplication.run(BeanApp.class);
    }

    @Autowired
    ApplicationContext context;
  
    @GetMapping("/print")
    public String printBeans(){
        String[] names = context.getBeanNamesForType(MyBean.class);
        for (String name : names) {
            System.out.println(name);
        }
        return "";
    }
}

打印

getMyBean
bean2

依赖注入（设值注入）

  • @Autowired 默认根据类型获取bean，如果存在多个则按照属性名查找

  • @Resource 默认根据名称进行注解

public class InjectBean {
    private String id;

    public InjectBean(String id) {
        this.id = id;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }
}

/**
 * 依赖注入
 * {@link InjectBean}
 */
@Configuration
public class InjectBeanConfig {
    @Bean
    public InjectBean myBean1(){
        return new InjectBean("1");
    }
    @Bean
    public InjectBean myBean2(){
        return new InjectBean("2");
    }
}

使用

 @Resource(name = "myBean1")
    InjectBean myBean1;
    @Autowired     //默认根据类型获取bean，如果存在多个则按照属性名查找
    InjectBean myBean2;

构造注入（需要用@Autowired ）

  //构造注入
    InjectBean myBean;
    @Autowired
    public BeanApp(InjectBean myBean2) {
        this.myBean = myBean2;
    }

@Primary

@Configuration
public class PrimaryBeanConfig {
    @Bean
    @Primary  //主要的
    public PrimaryBean primaryBean1(){
        return new PrimaryBean("1");
    }
    @Bean
    public PrimaryBean primaryBean2(){
        return new PrimaryBean("2");
    }
}

使用

    @Autowired
    PrimaryBean bean;

    @GetMapping
    public String primary(){
        System.out.println(bean.getId());
        return "";
    }

@Scope --bean的作用域

/**
 * bean的作用域
 * {@link ScopeBean}
 */
@Configuration
public class ScopeBeanConfig {
    @Bean
    @Scope(value = ConfigurableBeanFactory.SCOPE_PROTOTYPE)//非单态
    public ScopeBean scopeBean1(){
        return new ScopeBean();
    }
    @Bean
    @Scope(value = ConfigurableBeanFactory.SCOPE_SINGLETON)//单态
    public ScopeBean scopeBean2(){
        return new ScopeBean();
    }
}

使用

  // 非单态每次都返回一个新的实例
    @GetMapping("/scope")
    public String scope(){
        System.out.println("非单态:"+context.getBean("scopeBean1"));
        System.out.println("单态:"+context.getBean("scopeBean2"));
        //非单态:com.anocation.vo.ScopeBean@4b100739
        //单态:com.anocation.vo.ScopeBean@5fce816b
        //非单态:com.anocation.vo.ScopeBean@413ac5e8
        //单态:com.anocation.vo.ScopeBean@5fce816b
        //非单态:com.anocation.vo.ScopeBean@697a5a81
        //单态:com.anocation.vo.ScopeBean@5fce816b
        return "";
    }

    //注入一个非单态的bean
    @Autowired
    private ScopeBean scopeBean1;
    //springmvc的控制器是单态的，多次调用会是同一个实例
    @GetMapping
    public String scopeBean1(){
        System.out.println(scopeBean1);
        return "";
    }

方法注入

使用场景：一个单态的bean使用一个非单态度的bean

  • 方法一
    private ScopeBean getScopeBean(){
        //通过注入的ApplicationContext返回非单态的bean
        return (ScopeBean) context.getBean("scopeBean1");
    }
    @GetMapping
    public String getScopeBean1(){
        System.out.println(getScopeBean());
        return "";
    }

  • 方法二

        @Lookup("scopeBean1")
    public abstract ScopeBean createScopeBean();

    @GetMapping
    public String lookupCreateScopeBean(){
        System.out.println(createScopeBean());
        return "";
    }

AOP注解

        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
        </dependency>

@Aspect
@Component
public class AopProxyConfig {
    //*： 匹配任意数量的字符
    //..：一般用于匹配任意数量的子包或参数
    @Pointcut("execution(* com.anocation.Testcontroller..*.*(..))")
    private void Pointcut(){}

    @Before("Pointcut()")
    public void before(){
        System.out.println("调用前");
    }
    @After("Pointcut()")
    public void after(){
        System.out.println("调用后");
    }
}

    public static void main(String[] args){
        //默认使用CGLIB代理
        //spring.aop.proxy-target-class=false,将使用jdk动态代理
        new SpringApplicationBuilder(BeanApp.class)
                .properties("spring.aop.proxy-target-class=false")
                .run();
    }

@ComponentScan

@SpringBootConfiguration
@EnableAutoConfiguration
//@ComponentScan(basePackages = "com.anocation.beanConfig")
@ComponentScan(basePackages = "com.anocation.beanConfig"
        ,excludeFilters = {@ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE,classes = MyConfig.class)})
@RestController
public class ScanApp {
    public static void main(String[] args){
        SpringApplication.run(ScanApp.class);
    }
    @Autowired
    private ApplicationContext context;

    //org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'bean2' available
    @GetMapping
    public String scan(){
        System.out.println(context.getBean("bean2"));
        return "";
    }
}

spring高级注解

限定注解 -- @Qualifier

@Configuration
public class beanConfig {
    @Bean
    public MyBean2 myBeanA(){
        return new MyBean2("a");
    }
    @Bean
    public MyBean2 myBeanB(){
        return new MyBean2("b");
    }
}

/**
 * 限定注解
 */
@SpringBootApplication(scanBasePackages = "com.anocation.beanConfig2")
@RestController
public class QualifierController {
    public static void main(String[] args){
        SpringApplication.run(QualifierController.class);
    }
    @Autowired
    @Qualifier("myBeanA")//指定注入名称为myBeanA的bean
    MyBean2 myBean;

    @GetMapping
    public String myBeanA(){
        System.out.println(myBean.getId());
        return "";
    }
}

自定义限定注解

@Target({ElementType.FIELD,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Qualifier
public @interface AnimalQualifier {
    String type();
}

@Configuration
public class CustomConfig {
    @Bean
    @AnimalQualifier(type = "dog")
    public MyBean2 dogBean(){
        return new MyBean2("Tyke");
    }
    @Bean
    @AnimalQualifier(type = "cat")
    public MyBean2 catBean(){
        return new MyBean2("Tom");
    }
}

使用

    @Autowired
    @AnimalQualifier(type = "cat")
    private MyBean2 myBean;

    @GetMapping
    public String myBeanA(){
        System.out.println(myBean.getId());
        return "";
    }

自定义bean的生命周期--通过自定义Scope实现

public class ScopeBean {
}

/**
 * 自定义Scope
 * import org.springframework.beans.factory.config.Scope;
 */
public class MyScope implements Scope {
    // 记录bean的使用次数
    private Map<String, Integer> beanCounts = new HashMap<>();
    //保存实例
    private Map<String, Object> beans = new HashMap<>();
    @Override
    public Object get(String name, ObjectFactory<?> objectFactory) {
        if (beanCounts.get(name)==null){
            beanCounts.put(name,0);
        }
        Integer beanCount = beanCounts.get(name);
        if (beanCount==0){
            Object object = objectFactory.getObject();
            beans.put(name,object);
        }
        Object bean = beans.get(name);
        Integer newBeanCount = beanCount+ 1;
        if (newBeanCount>=4){
            newBeanCount = 0;
        }
        beanCounts.put(name,newBeanCount);
        return bean;
    }

    @Override
    public Object remove(String s) {
        return null;
    }

    @Override
    public void registerDestructionCallback(String s, Runnable runnable) {

    }

    @Override
    public Object resolveContextualObject(String s) {
        return null;
    }

    @Override
    public String getConversationId() {
        return null;
    }
}


/**
 * 自定义范围配置器
 */
@Configuration
public class ScopeConfig {
    @Autowired
    BeanFactory factory;
    @PostConstruct
    public void customScopeConfigurer(){
        CustomScopeConfigurer configurer = new CustomScopeConfigurer();
        configurer.addScope("four",new MyScope());
        configurer.postProcessBeanFactory((ConfigurableListableBeanFactory) factory);
    }
    @Bean
    @Scope(scopeName = "four")
    public ScopeBean scopeBeanA(){
        return new ScopeBean();
    }
}

使用

    @Autowired
    private ApplicationContext context;
    @GetMapping
    public String scope(){
        for (int i = 0; i < 6; i++) {
            System.out.println(context.getBean("scopeBeanA"));
        }
        //com.anocation.vo.ScopeBean@1ae3b695
        //com.anocation.vo.ScopeBean@1ae3b695
        //com.anocation.vo.ScopeBean@1ae3b695
        //com.anocation.vo.ScopeBean@1ae3b695
        //com.anocation.vo.ScopeBean@70a28b2d
        //com.anocation.vo.ScopeBean@70a28b2d
        return "";
    }

springmvc注解

@MatrixVariable --矩阵变量

@Configuration
public class MyWebConfig extends WebMvcConfigurationSupport {
    @Override
    public RequestMappingHandlerMapping requestMappingHandlerMapping() {
        final RequestMappingHandlerMapping requestMappingHandlerMapping = super
                .requestMappingHandlerMapping();
        //设置不删除分号内容 ，即开启矩阵变量的支持
        requestMappingHandlerMapping.setRemoveSemicolonContent(false);
        return requestMappingHandlerMapping;
    }
}

@SpringBootApplication(scanBasePackages = "com.anocation.matrixConfig")
@RestController
public class MatrixController {
    public static void main(String[] args){
        SpringApplication.run(MatrixController.class);
    }

    // http://localhost:8080/car/100;color=red;year=1000
    @GetMapping("/car/{id}")
    public String path(@PathVariable Integer id,
                       @MatrixVariable String color,
                       @MatrixVariable String year){
        System.out.println("id = " + id);
        System.out.println("color = " + color);
        System.out.println("year = " + year);
        //id = 100
        //color = red
        //year = 1000
        return "";
    }
}

文件上传

 @RequestMapping("/upload")
    public String upload(@RequestParam("file")MultipartFile file) throws IOException {
        System.out.println(file.getBytes());
        return "";
    }

<form action="http://localhost:8080/upload" method="post" enctype="multipart/form-data">
    <input type="file" name="file">
    <input type="submit">
</form>

springboot的条件注解

类条件注解

当类路径中存在或不存在某个类时，再决定是否执行自动配置

@Configuration
public class OnClassConfig {
    @Bean
    @ConditionalOnMissingClass(value = "com.anocation.vo1.MyBean")
    public MyBean myBean(){
        return new MyBean();
    }

    @Bean
    @ConditionalOnClass(name = "com.anocation.vo.MyBean2")
    public MyBean2 myBean2(){
        return new MyBean2("a");
    }
}

@SpringBootApplication(scanBasePackages = "com.anocation.onclass")
@RestController
public class OnClassConfigApp {
    public static void main(String[] args){
        SpringApplication.run(OnClassConfigApp.class);
    }
    @Autowired
    private ApplicationContext context;
    @GetMapping
    public String test(){
        System.out.println(context.getBeansOfType(MyBean.class).size());
        System.out.println(context.getBeansOfType(MyBean2.class).size());
        return "";
    }
}

自定义条件注解

/**
 * import org.springframework.context.annotation.Condition;
 */
public class MyCondition implements Condition {
    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        Environment env = context.getEnvironment();
        String user = env.getProperty("jdbc.user");
        System.out.println(user);
        if ("root".equals(user)){
            return true;
        }
        return false;
    }
}

@Target({ElementType.TYPE,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Conditional(MyCondition.class)
public @interface ConditionOnMyTerm {
}

@ConditionOnMyTerm
@Configuration
public class MyConfig {
    @Bean
    public MyBean myBean(){
        return new MyBean();
    }
}

application.properties

jdbc.user=123

使用

@SpringBootApplication(scanBasePackages = "com.anocation.condition")
@RestController
public class ConditionOnMyTermApp {
    public static void main(String[] args){
        SpringApplication.run(ConditionOnMyTermApp.class);
    }
    @Autowired
    private ApplicationContext context;
    @GetMapping
    public String test(){
        System.out.println(context.getBeansOfType(MyBean.class).size());
        return "";
    }
}
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原文地址：https://www.cnblogs.com/fly-book/p/12187778.html