流程引擎Camunda開發(fā)記錄（二）中

一县忌、RESET API

REST API 的目標是提供對引擎所有相關接口的訪問。

Spring是用于開發(fā)企業(yè)級應用程序的流行框架断盛。經(jīng)過多年的發(fā)展苗沧，SpringBoot登上了舞臺。Spring是使用@RestController編寫RESTful Web服務个曙。

編寫RESTful Web服務的方法有很多锈嫩，Jersey是JAX-RS的開源框架實現(xiàn)，它是RESTful Web服務的Java API。JAX-RS是Java EE技術的一部分呼寸。

二那槽、如何在在Spring使用Jersey呢？

本文將學習如何使用Spring Boot和Jersey框架等舔，去配置和創(chuàng)建JAX-RS 2.0 REST API接口；
這個示例應用使用的是Jersey的Servlet容器去部署REST API接口糟趾；

（一）配置

工程目錄

image.png

1.訪問Spring Initializr網(wǎng)站慌植，添加Jersey (JAX-RS)依賴，點擊生成代碼义郑；
2.下載代碼到本地蝶柿，解壓，導入代碼到IDE中
3.檢查下pom.xml代碼里是否包含了spring-boot-starter-jersey依賴非驮；

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-jersey</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

（二）創(chuàng)建JAX-RS REST資源

先創(chuàng)建一個UserResource類交汤，代碼如下：
UserResource.java

package com.howtodoinjava.jerseydemo;
 
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
 
import javax.ws.rs.Consumes;
import javax.ws.rs.DELETE;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.PUT;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Response;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlRootElement;
 
@XmlAccessorType(XmlAccessType.NONE)
@XmlRootElement(name = "users")
@Path("/users")
public class UserResource
{
    private static Map<Integer, User> DB = new HashMap<>();
     
    @GET
    @Produces("application/json")
    public Users getAllUsers() {
        Users users = new Users();
        users.setUsers(new ArrayList<>(DB.values()));
        return users;
    }
     
    @POST
    @Consumes("application/json")
    public Response createUser(User user) throws URISyntaxException
    {
        if(user.getFirstName() == null || user.getLastName() == null) {
            return Response.status(400).entity("Please provide all mandatory inputs").build();
        }
        user.setId(DB.values().size()+1);
        user.setUri("/user-management/"+user.getId());
        DB.put(user.getId(), user);
        return Response.status(201).contentLocation(new URI(user.getUri())).build();
    }
 
    @GET
    @Path("/{id}")
    @Produces("application/json")
    public Response getUserById(@PathParam("id") int id) throws URISyntaxException
    {
        User user = DB.get(id);
        if(user == null) {
            return Response.status(404).build();
        }
        return Response
                .status(200)
                .entity(user)
                .contentLocation(new URI("/user-management/"+id)).build();
    }
 
    @PUT
    @Path("/{id}")
    @Consumes("application/json")
    @Produces("application/json")
    public Response updateUser(@PathParam("id") int id, User user) throws URISyntaxException
    {
        User temp = DB.get(id);
        if(user == null) {
            return Response.status(404).build();
        }
        temp.setFirstName(user.getFirstName());
        temp.setLastName(user.getLastName());
        DB.put(temp.getId(), temp);
        return Response.status(200).entity(temp).build();
    }
 
    @DELETE
    @Path("/{id}")
    public Response deleteUser(@PathParam("id") int id) throws URISyntaxException {
        User user = DB.get(id);
        if(user != null) {
            DB.remove(user.getId());
            return Response.status(200).build();
        }
        return Response.status(404).build();
    }
     
    static
    {
        User user1 = new User();
        user1.setId(1);
        user1.setFirstName("John");
        user1.setLastName("Wick");
        user1.setUri("/user-management/1");
 
        User user2 = new User();
        user2.setId(2);
        user2.setFirstName("Harry");
        user2.setLastName("Potter");
        user2.setUri("/user-management/2");
         
        DB.put(user1.getId(), user1);
        DB.put(user2.getId(), user2);
    }
}

（三）Users.java

package com.howtodoinjava.jerseydemo;
  
import java.util.ArrayList;
 
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
  
@XmlAccessorType(XmlAccessType.NONE)
@XmlRootElement(name = "users")
public class Users {
  
    @XmlElement(name="user")
    private ArrayList<User> users;
  
    public ArrayList<User> getUsers() {
        return users;
    }
  
    public void setUsers(ArrayList<User> users) {
        this.users = users;
    }
}

（四）User.java

package com.howtodoinjava.jerseydemo;
  
import java.io.Serializable;
  
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
  
@XmlAccessorType(XmlAccessType.NONE)
@XmlRootElement(name = "user")
public class User implements Serializable {
  
    private static final long serialVersionUID = 1L;
  
    @XmlAttribute(name = "id")
    private int id;
  
    @XmlAttribute(name="uri")
    private String uri;
  
    @XmlElement(name = "firstName")
    private String firstName;
  
    @XmlElement(name = "lastName")
    private String lastName;
  
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public String getUri() {
        return uri;
    }
    public void setUri(String uri) {
        this.uri = uri;
    }
}

（五）配置Jersey

到目前為止，我們已經(jīng)創(chuàng)建了一個JAX-RS資源劫笙，現(xiàn)在我們想通過spring boot應用去訪問它芙扎，步驟如下；
1.首先我們要注冊改資源為Jersey資源填大，代碼如下：

package com.howtodoinjava.jerseydemo;
 
import org.glassfish.jersey.server.ResourceConfig;
import org.springframework.stereotype.Component;
 
@Component
public class JerseyConfig extends ResourceConfig
{
    public JerseyConfig()
    {
        register(UserResource.class);
    }
}

注意需要加上 @Component注解戒洼，以便Spring Boot能夠掃描到；
2.其次JerseyConfig需要繼承ResourceConfig允华，該類提供了很多高級功能圈浇，簡化了JAX-RS組件的注冊工作；
3.最后Spring Boot Application啟動類需要繼承SpringBootServletInitializer

package com.howtodoinjava.jerseydemo;
 
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.support.SpringBootServletInitializer;
 
@SpringBootApplication
public class JerseydemoApplication extends SpringBootServletInitializer
{
    public static void main(String[] args)
    {
        new JerseydemoApplication().configure(new SpringApplicationBuilder(JerseydemoApplication.class)).run(args);
    }
}

（六）演示

啟動Spring Boot應用靴寂，訪問user 資源