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阿新 • • 發佈：2021-01-26
總結
springboot如何開啟自動配置
1、main方法所在類的@SpringBootApplication註解
@SpringBootApplication <-----------------註解
public class SpringbootQuickApplication {
public static void main(String[] args) 2、點進去註解類上有一個@EnableAutoConfiguration
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration <--------------註解
@ComponentScan(
excludeFilters = 3、點進註解類上有一個註解
@Import{AutoConfigurationImportSelector.class}
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import({AutoConfigurationImportSelector.class})
public @interface EnableAutoConfiguration {
String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration";
Class<?>[] exclude() default {};
String[] excludeName() default {};
}在AutoConfigurationImportSelector類中會執行getCandidateConfigurations（AnnotationMetadata metadata,AnnotationAttributes attributes）方法裡面有一行：
List configurations = SpringFactoriesLoader.loadFactoryNames(
getSpringFactoriesLoaderFactoryClass(), getBeanClassLoader());
這裡就會掃描具有MEAT-INF/spring.factories檔案的jar包，得到所有的配置類：
protected List<String> getCandidateConfigurations(AnnotationMetadata metadata,
AnnotationAttributes attributes) {
List<String> configurations = SpringFactoriesLoader.loadFactoryNames
(this.getSpringFactoriesLoaderFactoryClass(), this.getBeanClassLoader());
return configurations;
}4、找到spring.factories檔案的內容看下
4.1、spring.factories自動注入的內容
# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\
org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\
org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration,\
org.springframework.boot.autoconfigure.batch.BatchAutoConfiguration,\
org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration,\
org.springframework.boot.autoconfigure.cassandra.CassandraAutoConfiguration,\
org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration,\
org.springframework.boot.autoconfigure.context.LifecycleAutoConfiguration,\
org.springframework.boot.autoconfigure.context.MessageSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration,\
org.springframework.boot.autoconfigure.couchbase.CouchbaseAutoConfiguration,\
org.springframework.boot.autoconfigure.dao.PersistenceExceptionTranslationAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveDataAutoConfiguration,\
4.2、解釋幾個註解
@SpringBootApplication：啟動stringboot環境
@ComponentScan：配置包掃描
@ImportResource：引入自定義配置檔案
springboot如何處理異常的
1 、自定義錯誤頁面
如 果 我 們 需 要 將 所 有 的 異 常 同 一 跳 轉 到 自 定 義 的 錯 誤 頁 面
需 要 再src/main/resources/templates 目錄下建立 error.html 頁面。注意：名稱必須叫 error
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>錯誤提示頁面</title>
</head>
<body>
錯了 我不giao了
<span th:text="${exception}"></span>
</body>
</html>2、@ExceptionHandle 註解處理異常
上一種方法不管發生什麼異常，都只能跳轉到一個頁面，顆粒度太大而這一種方式可以實現對不同的異常做不同的處理
@Controller
public class DemoController {
@RequestMapping("/show")
public String showInfo(){
String str = null;
str.length();
return "index";
}
@RequestMapping("/show2")
public String showInfo2(){
int a = 10/0;
return "index";
}
// 算數錯誤
@ExceptionHandler(value={java.lang.ArithmeticException.class})
public ModelAndView arithmeticExceptionHandler(Exception e){
ModelAndView mv = new ModelAndView();
mv.addObject("error", e.toString());
mv.setViewName("error1");
return mv;
}
//空指標異常
@ExceptionHandler(value={java.lang.NullPointerException.class})
public ModelAndView nullPointerExceptionHandler(Exception e){
ModelAndView mv = new ModelAndView();
mv.addObject("error", e.toString());
mv.setViewName("error2");
return mv;
}
頁面1
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>錯誤提示頁面-ArithmeticException</title>
</head>
<body>
出錯了，請與管理員聯絡。。。
<span th:text="${error}"></span>
</body>
</html>
頁面2
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>錯誤提示頁面-NullPointerException</title>
</head>
<body>
<span th:text="${error}"></span>
</body>
</html>
3、@[email protected] 註解處理異常
上一種方式必須要在每一個Controler裡面重複寫異常處理程式碼，程式碼複用性太差，這一種方法可以實現異常的全域性處理。需要建立一個能夠處理異常的全域性異常類。在該類上需要新增@ControllerAdvice 註解
@ControllerAdvice
public class GlobalException {
//java.lang.ArithmeticException
@ExceptionHandler(value={java.lang.ArithmeticException.class})
public ModelAndView arithmeticExceptionHandler(Exception e){
ModelAndView mv = new ModelAndView();
mv.addObject("error", e.toString());
mv.setViewName("error1");
return mv;
}
//java.lang.NullPointerException
ExceptionHandler(value={java.lang.NullPointerException.class})
public ModelAndView nullPointerExceptionHandler(Exception e){
ModelAndView mv = new ModelAndView();
mv.addObject("error", e.toString());
mv.setViewName("error2");
return mv;
}
}
} 4、配置 SimpleMappingExceptionResolver 處理異常
//通過 SimpleMappingExceptionResolver 做全域性異常處理
@Configuration
public class GlobalException {
//該方法必須要有返回值。返回值型別必須是：SimpleMappingExceptionResolver
@Bean
public SimpleMappingExceptionResolver
getSimpleMappingExceptionResolver(){
SimpleMappingExceptionResolver resolver = new
SimpleMappingExceptionResolver();
Properties mappings = new Properties();
/**
* 引數一：異常的型別，注意必須是異常型別的全名
* 引數二：檢視名稱
*/
mappings.put("java.lang.ArithmeticException", "error1");
mappings.put("java.lang.NullPointerException","error2");
//設定異常與檢視對映資訊的
resolver.setExceptionMappings(mappings);
return resolver;
}
}5、自定義 HandlerExceptionResolver 類處理異常
/**
* 通過實現 HandlerExceptionResolver 介面做全域性異常處理
*/
@Configuration
public class GlobalException implements HandlerExceptionResolver {
@Override
public ModelAndView resolveException(HttpServletRequest request,
HttpServletResponse response, Object handler,Exception ex) {
ModelAndView mv = new ModelAndView();
//判斷不同異常型別，做不同檢視跳轉
if(ex instanceof ArithmeticException){
mv.setViewName("error1");
}
if(ex instanceof NullPointerException){
mv.setViewName("error2");
}
mv.addObject("error", ex.toString());
return mv;
}
}在springboot中，如何使用攔截器?
1、實現攔截器
public class InterceptorDemo extends HandlerInterceptorAdapter {
@Override
public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
StringBuffer requestURL = httpServletRequest.getRequestURL();
System.out.println("前置攔截器1 preHandle： 請求的uri為："+requestURL.toString());
return true;
}
@Override
public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
System.out.println("攔截器1 postHandle： ");
}
@Override
public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
System.out.println("攔截器1 afterCompletion： ");
}
}
2、註冊攔截器
@Configuration
public class InterceptorConfig implements WebMvcConfigurer{
//註冊自定義攔截器
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(new InterceptorDemo2()).addPathPatterns("/**");
registry.addInterceptor(new InterceptorDemo()).addPathPatterns("/**");
}
}在springboot中，如何擴充套件springmvc的功能
@Configuration <-----註解
public class WebMVCConfig implements WebMvcConfigurer { <----實現WebMvcConfigurer
@Override
public void addViewControllers(ViewControllerRegistry registry) {
registry.addViewController("/").setViewName("index");
registry.addViewController("/index.html").setViewName("index");
registry.addViewController("/index").setViewName("index");
//定義跳轉到主頁面的檢視
registry.addViewController("/dashboard.html").setViewName("dashboard");
}
}