关于java:SpringMVC-解析五URI链接处理

URI在网络申请中必不可少，Spring提供了一些工具类用于解析或者生成URL，比方依据参数生成GET的URL等。本文会对Spring MVC中的URI工具进行介绍，本文次要参考Spring官网文档。

<!–more–>

工具类UriComponents

UriComponentsBuilder能够用于依据URL和参数来构建门路，比方咱们须要一个带GET参数的URL，通常状况下咱们须要本人去拼接URL，增加”&”和”?等参数”。UriComponentsBuilder提供一种更简介的办法去构建URL：

UriComponents uriComponents = UriComponentsBuilder
        .fromUriString("https://example.com/hotels/{hotel}")  
        .queryParam("q", "{q}")  
        .encode() 
        .build(); 

// https://example.com/hotels/Westin?q=123
URI uri = uriComponents.expand("Westin", "123").toUri();  

下面的两条语句也能够合并到一个Build链中，用如下形式达到同样的目标：

URI uri = UriComponentsBuilder
        .fromUriString("https://example.com/hotels/{hotel}")
        .queryParam("q", "{q}")
        .encode()
        .buildAndExpand("Westin", "123")
        .toUri();

URI uri = UriComponentsBuilder
        .fromUriString("https://example.com/hotels/{hotel}")
        .queryParam("q", "{q}")
        .build("Westin", "123");

URI uri = UriComponentsBuilder
        .fromUriString("https://example.com/hotels/{hotel}?q={q}")
        .build("Westin", "123");

接口UriBuilder

UriComponentsBuilder实现了UriBuilder接口，该接口的次要性能就是构建Uri。Spring中能够通过UriBuilderFactory获取UriBuilder的实例。咱们平时应用httpClient类如Spring的RestTemplate，并不需要本人拼接Uri，只须要输出参数组件会主动拼接Url。对于过Spring的RestTemplate，其外部应用的Url组件就是UriBuilderFactory。

// import org.springframework.web.util.DefaultUriBuilderFactory.EncodingMode;

String baseUrl = "https://example.org";
DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory(baseUrl);
factory.setEncodingMode(EncodingMode.TEMPLATE_AND_VALUES);

RestTemplate restTemplate = new RestTemplate();
restTemplate.setUriTemplateHandler(factory);

// import org.springframework.web.util.DefaultUriBuilderFactory.EncodingMode;

String baseUrl = "https://example.org";
DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory(baseUrl);
factory.setEncodingMode(EncodingMode.TEMPLATE_AND_VALUES);

WebClient client = WebClient.builder().uriBuilderFactory(factory).build();

String baseUrl = "https://example.com";
DefaultUriBuilderFactory uriBuilderFactory = new DefaultUriBuilderFactory(baseUrl);

URI uri = uriBuilderFactory.uriString("/hotels/{hotel}")
        .queryParam("q", "{q}")
        .build("Westin", "123");

Url的编码

UriComponentsBuilder组件提供了两种类型的编码方式：

• UriComponentsBuilder#encode()：对Url模板和参数别离进行编码之后进行拼接。
• UriComponents#encode()：对拼接后的Url进行编码操作。

大多数状况下适宜应用UriComponentsBuilder#encode()，因为它将参数独自进行了编码。然而如果你须要在编码中保留特殊字符，那么最好应用第二种编码方式。

URI uri = UriComponentsBuilder.fromPath("/hotel list/{city}")
        .queryParam("q", "{q}")
        .encode()
        .buildAndExpand("New York", "foo+bar")
        .toUri();

// Result is "/hotel%20list/New%20York?q=foo%2Bbar"

Servlet Uri构建

Spring提供了另一个Uri组件ServletUriComponentsBuilder，该组件能够基于Servlet申请构建新的Uri：

HttpServletRequest request = ...

// Re-uses host, scheme, port, path and query string...
ServletUriComponentsBuilder ucb = ServletUriComponentsBuilder.fromRequest(request)
        .replaceQueryParam("accountId", "{id}").build()
        .expand("123")
        .encode();

// Re-uses host, port and context path...
ServletUriComponentsBuilder ucb = ServletUriComponentsBuilder.fromContextPath(request).path("/accounts").build()

// Re-uses host, port, context path, and Servlet prefix...
ServletUriComponentsBuilder ucb = ServletUriComponentsBuilder.fromServletMapping(request).path("/accounts").build()

Controller Uri

咱们晓得Spring中能够通过@RequestMapping把一个申请映射到Controller的办法上，那么咱们如何获取到Controller办法的申请门路呢？

@Controller
@RequestMapping("/hotels/{hotel}")
public class BookingController {

    @GetMapping("/bookings/{booking}")
    public ModelAndView getBooking(@PathVariable Long booking) {
        // ...
    }
}

Spring 提供了MvcUriComponentsBuilder工具获取Controller办法对应的门路，其应用示例如下所示：

// 21:指明参数的类型, 42:新的参数类型. 
UriComponents uriComponents = MvcUriComponentsBuilder
    .fromMethodName(BookingController.class, "getBooking", 21).buildAndExpand(42);

URI uri = uriComponents.encode().toUri();

UriComponents uriComponents = MvcUriComponentsBuilder
    .fromMethodCall(on(BookingController.class).getBooking(21)).buildAndExpand(42);

URI uri = uriComponents.encode().toUri();

Controller办法应该是非Final的，否则Spring可能会获取不到配置的门路信息。

MvcUriComponentsBuilder 还反对指定Context，如域名等信息，示例如下所示：

UriComponentsBuilder base = ServletUriComponentsBuilder.fromCurrentContextPath().path("/en");
MvcUriComponentsBuilder builder = MvcUriComponentsBuilder.relativeTo(base);
builder.withMethodCall(on(BookingController.class).getBooking(21)).buildAndExpand(42);

URI uri = uriComponents.encode().toUri();

视图中的URL

在Thymeleaf、FreeMarker和JSP等视图组件中，咱们能够通过视图URL组件去拼接URL，示例如下：

@RequestMapping("/people/{id}/addresses")
public class PersonAddressController {

    @RequestMapping("/{country}")
    public HttpEntity<PersonAddress> getAddress(@PathVariable String country) { ... }
}

<%@ taglib uri="http://www.springframework.org/tags" prefix="s" %>
...
<a href="${s:mvcUrl('PAC#getAddress').arg(0,'US').buildAndExpand('123')}">Get Address</a>

本文最先公布至微信公众号，版权所有，禁止转载！