同样，在 SSH 工具出现之前 R 系列命令也很流行（由于这些命令都以字母 r 开头，故把这些命令合称为 R 系列命令，R 是 remote 的意思），比如 rexec 是用来执行远程服务器上的命令的，和 telnet 的区别是 telnet 需要先登录远程服务器再实行相关的命令，而 R 系列命令可以把登录和执行命令并登出系统的操作整合在一起。这样就不需要为在远程服务器上执行一个命令而特地登录服务器了。
SSH 全称 Secure SHell，顾名思义就是非常安全的 shell 的意思，SSH 协议是 IETF（Internet Engineering Task Force） 的 Network Working Group 所制定的一种协议。SSH 的主要目的是用来取代传统的 telnet 和 R 系列命令（rlogin、rsh、rexec 等）远程登录和远程执行命令的工具，实现对远程登录和远程执行命令加密。防止由于网络监听而出现的密码泄漏，对系统构成威胁。
usage: ssh-add [options] [file ...] Options: -l List fingerprints of all identities. -E hash Specify hash algorithm used for fingerprints. -L List public key parameters of all identities. -k Load only keys and not certificates. -c Require confirmation to sign using identities -t life Set lifetime (in seconds) when adding identities. -d Delete identity. -D Delete all identities. -x Lock agent. -X Unlock agent. -s pkcs11 Add keys from PKCS#11 provider. -e pkcs11 Remove keys provided by PKCS#11 provider.
Traditional MVC controller relying on a view technology to perform server-side rendering.
@RestController
RESTful web service controller simply populates and returns a object that will be written directly to the HTTP response as JSON. Thanks to Spring’s HTTP message converter support, you don’t need to do this conversion manually. Because Jackson 2 is on the classpath, Spring’s MappingJackson2HttpMessageConverter is automatically chosen to convert the object to JSON.
It’s shorthand for @Controller and @ResponseBody rolled together.
Annotation which indicates that a method parameter should be bound to a web request parameter.
Supported for annotated handler methods in Spring MVC and Spring WebFlux as follows:
In Spring MVC, “request parameters” map to query parameters, form data, and parts in multipart requests. This is because the Servlet API combines query parameters and form data into a single map called “parameters”, and that includes automatic parsing of the request body.
In Spring WebFlux, “request parameters” map to query parameters only. To work with all 3, query, form data, and multipart data, you can use data binding to a command object annotated with ModelAttribute.
If the method parameter type is Map and a request parameter name is specified, then the request parameter value is converted to a Map assuming an appropriate conversion strategy is available.
If the method parameter is Map or MultiValueMap and a parameter name is not specified, then the map parameter is populated with all request parameter names and values.
例子 1：POST with form data
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POST /test HTTP/1.1 Host: localhost:8080 Content-Type: application/x-www-form-urlencoded
data=123,234
例子 2：GET with query string parameters
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GET /test?data=123,234 HTTP/1.1 Host: localhost:8080
Type conversion is applied automatically if the target method parameter type is not String. See the section called “Method Parameters And Type Conversion”.
When an @RequestParam annotation is used on a Map<String, String> or MultiValueMap<String, String> argument, the map is populated with all request parameters.
An @RequestBody method parameter can be annotated with @Valid, in which case it will be validated using the configured Validator instance. When using the MVC namespace or the MVC Java config, a JSR-303 validator is configured automatically assuming a JSR-303 implementation is available on the classpath.
Classes annotated with @ControllerAdvice can contain @ExceptionHandler, @InitBinder, and @ModelAttribute annotated methods, and these methods will apply to @RequestMapping methods across all controller hierarchies as opposed to the controller hierarchy within which they are declared.
@RestControllerAdvice is an alternative where @ExceptionHandler methods assume @ResponseBody semantics by default.
Both @ControllerAdvice and @RestControllerAdvice can target a subset of controllers:
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// Target all Controllers annotated with @RestController @ControllerAdvice(annotations = RestController.class) public class AnnotationAdvice {}
// Target all Controllers within specific packages @ControllerAdvice("org.example.controllers") public class BasePackageAdvice {}
// Target all Controllers assignable to specific classes @ControllerAdvice(assignableTypes = {ControllerInterface.class, AbstractController.class}) public class AssignableTypesAdvice {}
