@SuppressWarnings注解详细解析

傷城~ 2024-04-21 19:05 74阅读 0赞

### 前言 ###

`@SuppressWarnings`注解屏蔽一些错误警告，但不是代码错误，这个注解可以提高代码的安全性，防止为了解决这个错误警告而造成不可估量的后果

### 1. 源码 ###

通过学习注解上的源码以及官方文档  
可以了解更加透彻

@Target({
        TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
    @Retention(RetentionPolicy.SOURCE)
    public @interface SuppressWarnings {
        
        /**
         * The set of warnings that are to be suppressed by the compiler in the
         * annotated element.  Duplicate names are permitted.  The second and
         * successive occurrences of a name are ignored.  The presence of
         * unrecognized warning names is <i>not</i> an error: Compilers must
         * ignore any warning names they do not recognize.  They are, however,
         * free to emit a warning if an annotation contains an unrecognized
         * warning name.
         *
         * <p> The string {@code "unchecked"} is used to suppress
         * unchecked warnings. Compiler vendors should document the
         * additional warning names they support in conjunction with this
         * annotation type. They are encouraged to cooperate to ensure
         * that the same names work across multiple compilers.
         * @return the set of warnings to be suppressed
         */
        String[] value();
    }

通过`@SuppressWarnings`的源码可知，其注解目标为类、字段、函数、函数入参、构造函数和函数的局部变量

*  用于抑制编译器产生警告信息

### 2. 抑制警告的值 ###

<table> 
 <thead> 
  <tr> 
   <th>值</th> 
   <th>作用</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>all</td> 
   <td>to suppress all warnings （抑制所有警告）</td> 
  </tr> 
  <tr> 
   <td>boxing</td> 
   <td>to suppress warnings relative to boxing/unboxing operations （抑制装箱、拆箱操作时候的警告）</td> 
  </tr> 
  <tr> 
   <td>cast</td> 
   <td>to suppress warnings relative to cast operations （抑制映射相关的警告）</td> 
  </tr> 
  <tr> 
   <td>dep-ann</td> 
   <td>to suppress warnings relative to deprecated annotation （抑制启用注释的警告）</td> 
  </tr> 
  <tr> 
   <td>deprecation</td> 
   <td>to suppress warnings relative to deprecation （抑制过期方法警告）</td> 
  </tr> 
  <tr> 
   <td>fallthrough</td> 
   <td>to suppress warnings relative to missing breaks in switch statements （抑制确在switch中缺失breaks的警告）</td> 
  </tr> 
  <tr> 
   <td>finally</td> 
   <td>to suppress warnings relative to finally block that don’t return （抑制finally模块没有返回的警告）</td> 
  </tr> 
  <tr> 
   <td>hiding</td> 
   <td>to suppress warnings relative to locals that hide variable（抑制相对于隐藏变量的局部变量的警告）</td> 
  </tr> 
  <tr> 
   <td>incomplete-switch</td> 
   <td>to suppress warnings relative to missing entries in a switch statement (enum case)（忽略没有完整的switch语句）</td> 
  </tr> 
  <tr> 
   <td>nls</td> 
   <td>to suppress warnings relative to non-nls string literals（ 忽略非nls格式的字符）</td> 
  </tr> 
  <tr> 
   <td>null</td> 
   <td>to suppress warnings relative to null analysis（ 忽略对null的操作）</td> 
  </tr> 
  <tr> 
   <td>rawtypes</td> 
   <td>to suppress warnings relative to un-specific types when using generics on class params（ 使用generics时忽略没有指定相应的类型）</td> 
  </tr> 
  <tr> 
   <td>restriction</td> 
   <td>to suppress warnings relative to usage of discouraged or forbidden references（ 抑制禁止使用劝阻或禁止引用的警告）</td> 
  </tr> 
  <tr> 
   <td>serial</td> 
   <td>to suppress warnings relative to missing serialVersionUID field for a serializable class（ 忽略在serializable类中没有声明serialVersionUID变量）</td> 
  </tr> 
  <tr> 
   <td>static-access</td> 
   <td>to suppress warnings relative to incorrect static access（ 抑制不正确的静态访问方式警告）</td> 
  </tr> 
  <tr> 
   <td>synthetic-access</td> 
   <td>to suppress warnings relative to unoptimized access from inner classes（ 抑制子类没有按最优方法访问内部类的警告）</td> 
  </tr> 
  <tr> 
   <td>unchecked</td> 
   <td>to suppress warnings relative to unchecked operations（ 抑制没有进行类型检查操作的警告）</td> 
  </tr> 
  <tr> 
   <td>unqualified-field-access</td> 
   <td>to suppress warnings relative to field access unqualified（ 抑制没有权限访问的域的警告）</td> 
  </tr> 
  <tr> 
   <td>unused</td> 
   <td>to suppress warnings relative to unused code（ 抑制没被使用过的代码的警告）</td> 
  </tr> 
 </tbody> 
</table>

主要常用的值也就这几个

1.  `@SuppressWarnings("unchecked")` 抑制单类型的警告
2.  `@SuppressWarnings({"unchecked", "deprecated"})` 抑制多类型的警告
3.  `@SuppressWarnings("all")` 抑制所有类型的警告

*  `deprecation` 告诉编译器忽略过时的方法或类型检查

### 2. 代码示列 ###

@SuppressWarnings("all")
    @RunWith(SpringRunner.class)
    @SpringBootTest
    public class UserTest {
        
    
        //定义StudentMapper
        @Autowired
        private UserMapper userDao;
    
    
        @Test
        public void testInsertStudent() {
        
            User user = new User();
            user.setName("hh");
            user.setEmail("hh.com");
            user.setAge(20);
            
            int rows = userDao.insert(user);
            System.out.println("inserStudent rows:" + rows);
        }
    }