RESTful实战笔记一——REST介绍及JERSEY快速体验

偏执的太偏执、 2021-11-27 01:16 320阅读 0赞

# JAX-RS2入门 #

## 解读REST ##

（Representation State Transfer）表属性状态转移，六个特点：客户端-服务器的、无状态的、可缓存的、统一接口的、分层系统和按需编码。优势：跨平台、跨语言。

REST风格将对象视为一种资源（resource）。

REST资源可寻址：

HTTP协议定义通用动词方法（GET、POST、DELETE、PUT）；

URI协议唯一标识资源公布的接口。

标准：HTTP+URL+XML（XML借指数据格式），标准是基本实现格式，但是不是唯一实现形式。满足基本实现格式的不一定就是REST服务。

### REST对比RPC风格对比MVC风格 ###

REST风格更轻量和快捷。从方法角度看，REST采用标准的HTTP方法，而RPC请求都是采用POST方法，其方法信息包含于SOAP协议包或HTTP协议包中，方法名称不具有通用性。从作用于的角度来看，REST采用URI显示定义作用域，而RPC的这一信息包含于协议包中，不能直观呈现。

RPC是面向方法调用的过程，相对而言，REST是面向资源状态的。

MVC风格将模型、视图、控制解耦，从前到后的一致性，结构整洁逻辑清晰易于扩展和增强，REST风格偏重统一接口，可实现跨语言、跨平台解耦，推进了前后端分离。MVC和REST并不互斥

## RESTful Web Service（REST式Web服务） ##

REST服务是一种面向资源你的架构（ROA）应用，特点是方法信息存在于HTTP协议中，作用域存在于URI中。（区别RPC风格：RPC将请求方式放在信封中全部采用POST方法传送，没有体现HTTP协议的优势），所以REST风格更轻量和快速。

## JAX-RS2的目标 ##

要掌握一门技术，先要掌握其背后标准的定义。（我不想掌握jesery~）

1）基于POJO；

2）以HTTP为中心；

3）格式独立性；

4）容器独立性；

5）内置于javaEE；

# 为什么是JERSEY？ #

JERSEY框架从2019年起在github上不再更新？[https://github.com/jersey][https_github.com_jersey] 但是JERSEY是JAVA领域中最纯正的REST服务开发框架。来自GlassFish项目的子项目。

## JERSEY的模块 ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zODkzMDcwNg_size_16_color_FFFFFF_t_70][]

容器提供三种HTTP容器：Grizzly2、JDK-HTTP、SIMPLE-HTTP，Grizzly2同时提供Servlet容器。

# 快速实现Java REST服务 #

创建服务可以使用Jersey提供的Maven模型创建，使用IDEA创建快速启动的Jersey项目步骤如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zODkzMDcwNg_size_16_color_FFFFFF_t_70 1][]

GroupId：org.glassfish.jersey.archetypes

ArtifactId:jersey-quickstart-grizzly2

Version:2.22.1

创建完成后会生成如下的工程目录结构：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zODkzMDcwNg_size_16_color_FFFFFF_t_70 2][]

我们启动main方法，Jersey会启动web容器，我们根据uri访问便可完成简单的Jersey体验。

主类：

package my.restful;
    
    import java.io.IOException;
    import java.net.URI;
    
    import org.glassfish.grizzly.http.server.HttpServer;
    import org.glassfish.jersey.grizzly2.httpserver.GrizzlyHttpServerFactory;
    import org.glassfish.jersey.server.ResourceConfig;
    
    /**
     * Main class.
     */
    public class Main {
        // Base URI the Grizzly HTTP server will listen on
        public static final String BASE_URI = "http://localhost:8080/myapp/";
    
        /**
         * Starts Grizzly HTTP server exposing JAX-RS resources defined in this application.
         *
         * @return Grizzly HTTP server.
         */
        public static HttpServer startServer() {
            // create a resource config that scans for JAX-RS resources and providers
            // in my.restful package
            final ResourceConfig rc = new ResourceConfig().packages("my.restful");
    
            // create and start a new instance of grizzly http server
            // exposing the Jersey application at BASE_URI
            return GrizzlyHttpServerFactory.createHttpServer(URI.create(BASE_URI), rc);
        }
    
        /**
         * Main method.
         *
         * @param args
         * @throws IOException
         */
        public static void main(String[] args) throws IOException {
            final HttpServer server = startServer();
            System.out.println(String.format("Jersey app started with WADL available at "
                + "%sapplication.wadl\nHit enter to stop it...", BASE_URI));
            System.in.read();
            server.shutdown();
        }
    }

资源类：

package my.restful;
    
    import javax.ws.rs.GET;
    import javax.ws.rs.Path;
    import javax.ws.rs.Produces;
    import javax.ws.rs.core.MediaType;
    
    /**
     * Root resource (exposed at "myresource" path)
     */
    @Path("myresource")
    public class MyResource {
    
        /**
         * Method handling HTTP GET requests. The returned object will be sent
         * to the client as "text/plain" media type.
         *
         * @return String that will be returned as a text/plain response.
         */
        @GET
        @Produces(MediaType.TEXT_PLAIN)
        public String getIt() {
            return "Got it!";
        }
    }

请求uri：[http://localhost:8080/myapp/myresource][http_localhost_8080_myapp_myresource]

结果：![2019080714533666.png][]

## 扩展——webapp ##

webapp在jetty容器上提供rest服务：

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>my.restful</groupId>
        <artifactId>my-first-webapp</artifactId>
        <packaging>war</packaging>
        <version>1.0-SNAPSHOT</version>
        <name>my-first-webapp</name>
    
        <build>
            <finalName>my-first-webapp</finalName>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>2.5.1</version>
                    <inherited>true</inherited>
                    <configuration>
                        <source>1.7</source>
                        <target>1.7</target>
                    </configuration>
                </plugin>
                <plugin>
                    <groupId>org.eclipse.jetty</groupId>
                    <artifactId>jetty-maven-plugin</artifactId>
                    <version>9.3.5.v20151012</version>
                </plugin>
            </plugins>
        </build>
    
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.glassfish.jersey</groupId>
                    <artifactId>jersey-bom</artifactId>
                    <version>${jersey.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
    
        <dependencies>
            <dependency>
                <groupId>org.glassfish.jersey.containers</groupId>
                <artifactId>jersey-container-servlet-core</artifactId>
                
                
            </dependency>
            
            
            <dependency>
                <groupId>org.glassfish.jersey.containers</groupId>
                <artifactId>jersey-container-servlet</artifactId>
                <version>2.22.1</version>
            </dependency>
            <dependency>
                <groupId>org.glassfish.jersey.core</groupId>
                <artifactId>jersey-server</artifactId>
                <version>2.19</version>
            </dependency>
        </dependencies>
        <properties>
            <jersey.version>2.22.1</jersey.version>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        </properties>
    </project>

index.jsp

<html>
    <body>
        <h2>Jersey RESTful Web Application!</h2>
        <p><a href="webapi/myresource">Jersey resource</a>
        <p>Visit <a href="http://jersey.java.net">Project Jersey website</a>
        for more information on Jersey!
    </body>
    </html>

myResource.java

package my.restful;
    
    import java.util.concurrent.ConcurrentHashMap;
    
    import javax.ws.rs.Consumes;
    import javax.ws.rs.GET;
    import javax.ws.rs.POST;
    import javax.ws.rs.Path;
    import javax.ws.rs.PathParam;
    import javax.ws.rs.Produces;
    import javax.ws.rs.core.MediaType;
    
    /**
     * Root resource (exposed at "myresource" path)
     */
    @Path("myresource")
    public class MyResource {
    
        private static ConcurrentHashMap<String, MyDomain> map = new ConcurrentHashMap<>();
    
        /**
         * Method handling HTTP GET requests. The returned object will be sent
         * to the client as "text/plain" media type.
         *
         * @return String that will be returned as a text/plain response.
         */
        @GET
        @Produces(MediaType.TEXT_PLAIN)
        public String getIt() {
            return "Got it!";
        }
    
        @GET
        @Path("{key}")
        @Produces(MediaType.APPLICATION_XML)
        public MyDomain getMy(@PathParam("key") final String key) {
            final MyDomain myDomain = map.get(key);
            if (myDomain == null) {
                return new MyDomain();
            }
            return myDomain;
        }
    
        @POST
        @Consumes(MediaType.APPLICATION_XML)//POST传输application/xml
        public void addMy(final MyDomain myDomain) {
            map.put(myDomain.getName(), myDomain);
        }
    }

MyDomain.java

package my.restful;
    
    import javax.xml.bind.annotation.XmlAttribute;
    import javax.xml.bind.annotation.XmlRootElement;
    
    @XmlRootElement//对象转xml
    public class MyDomain {
        private String name;
        private String value;
    
        public MyDomain() {
        }
    
        public MyDomain(String name, String value) {
            this.name = name;
            this.value = value;
        }
    
        @XmlAttribute
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        @XmlAttribute
        public String getValue() {
            return value;
        }
    
        public void setValue(String value) {
            this.value = value;
        }
    }

测试：

无参访问:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zODkzMDcwNg_size_16_color_FFFFFF_t_70 3][]

带请求实体POST：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zODkzMDcwNg_size_16_color_FFFFFF_t_70 4][]

GET方法访问eric：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zODkzMDcwNg_size_16_color_FFFFFF_t_70 5][]

[https_github.com_jersey]: https://github.com/jersey
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zODkzMDcwNg_size_16_color_FFFFFF_t_70 1]: /images/20211126/d004741465e947ae8275ae9b8602b852.png
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[http_localhost_8080_myapp_myresource]: http://localhost:8080/myapp/myresource
[2019080714533666.png]: /images/20211126/2151f5ae53db4110a628dbe4253eec8b.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zODkzMDcwNg_size_16_color_FFFFFF_t_70 3]: /images/20211126/dc85f1a4a5d14da28c6b656602493e7e.png
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