setAttribute()方法——向request对象中存储数据 getAttribute()方法——从request对象中取数据
时间: 2024-11-07 13:13:49 浏览: 27
`setAttribute()` 方法用于在 `HttpServletRequest` 对象(Java Web开发中的 request对象)中存储数据,它可以用来保存任何类型的对象,包括自定义的对象实例[^1]。例如:
```java
// 储存一个字符串
String name = "John Doe";
request.setAttribute("username", name);
// 或者储存一个自定义对象
MyClass obj = new MyClass();
request.setAttribute("myObject", obj);
```
与此相反,`getAttribute()` 方法则是从 `HttpServletRequest` 对象中检索之前通过 `setAttribute()` 存储的数据。它只返回与给定名称关联的属性值,如果找不到则返回 `null`:
```java
// 取回字符串
String retrievedName = (String) request.getAttribute("username");
System.out.println(retrievedName); // 输出:John Doe
// 如果尝试取不存在的对象,会返回null
MyClass retrievedObj = (MyClass) request.getAttribute("myObject");
if (retrievedObj != null) {
System.out.println(retrievedObj.someMethod());
}
```
需要注意的是,`getAttribute()` 返回的总是原始类型,如果你存储的是一个对象,需要显式地转换回来。
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