采用gradle构建工具创建第一个基于jersey的Rest服务

REST是一种跨平台、跨语言的架构风格，RESTful Web Service是REST风格在Web领域的实现，JAX-RS标准是Java语言对RESTful Web Service的规范，Jersey是JAX-RS的参考实现，也是Java EE参考实现项目GlassFish的子项目；REST架构风格中各种抽象对象被描述为资源，资源的瞬时状态称为representation且可用XML/JSON/Atom等格式表示。RESTful Web Servcie也可以分解为类似MVC的三层结构，即资源、业务和数据访问对象，资源位于最前端用于接收请求和返回响应；JAX-RS2.0中定义的标准方法包括DELETE、GET、HEAD、OPTIONS、POST和PUT。

IDE采用IntelliJ IDEA Community Edition 14.1.2，构建工具采用gradle，创建gradle项目后，目录结构如下

由于本项目需要依赖jersey的相关包，因此作如下的配置，同时定义repositories为oschina镜像，否则无法拦截到mavencentral()。

build.gradle文件内容:

apply plugin: 'java'
apply plugin:'war'

version = '1.0'

repositories {
    maven {
        url 'http://maven.oschina.net/content/groups/public/'
    }
}
dependencies {
    compile group:'org.glassfish.jersey.containers',name:'jersey-container-grizzly2-http',version:'2.17'
    compile group:'org.glassfish.jersey.media',name:'jersey-media-json-jackson',version:'2.17'
    testCompile group: 'junit', name: 'junit', version: '4.11'
}

实体层：

@XmlRootElement(name="book")
public class Book {
    Integer id;
    String author;
    String bookName;
    String publisher;
    int price;

    public Book(Integer id, String author, String bookName, String publisher, int price) {
        this.id = id;
        this.author = author;
        this.bookName = bookName;
        this.publisher = publisher;
        this.price = price;
    }

    public void setId(Integer id){
        this.id=id;
    }
    @XmlAttribute
    public Integer getId(){
        return id;
    }
    @XmlAttribute
    public int getPrice() {
        return price;
    }

    public void setPrice(int price) {
        this.price = price;
    }
    @XmlAttribute
    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }
    @XmlAttribute
    public String getBookName() {
        return bookName;
    }

    public void setBookName(String bookName) {
        this.bookName = bookName;
    }
    @XmlAttribute
    public String getPublisher() {
        return publisher;
    }

    public void setPublisher(String publisher) {
        this.publisher = publisher;
    }
}

DAO层：

public class BookDao {
    Map<Integer,Book> books=new HashMap<Integer,Book>();
    private static int nextId=7;
    public BookDao(){

        books.put(1,new Book(1,"张三","C语言程序设计","简单出版社",29));
        books.put(2, new Book(2, "张三", "Java语言程序设计", "信息出版社", 43));
        books.put(3, new Book(3, "李四", "大学物理", "教育出版社", 22));
        books.put(4, new Book(4, "李四", "高等数学", "教育出版社", 43));
        books.put(5, new Book(5, "孔子", "论语", "春秋出版社", 53));
        books.put(6, new Book(6, "福布斯", "大学英语", "未名出版社", 22));
    }
    public Book get(Integer id){
        return books.get(id);
    }
    public boolean update(Book bk){
        if(bk.getId()==null)
        {
            bk.setId(nextId++);
        }
        books.put(bk.getId(),bk);
        return true;
    }
    public boolean delete(Integer id){
        if(books.remove(id)==null)
            return false;
        else
            return true;
    }
    public Map<Integer,Book> getAll(){
        return books;
    }
}

Web Service资源层：

@Path("books")
public class Books {
    private final BookDao bookDao;
    public Books() {
        bookDao = new BookDao();
    }
    @GET
    @Produces({MediaType.APPLICATION_JSON})
    public Map<Integer,Book> getAllBooks(){
        return bookDao.getAll();
    }
    @Path("book")
    @GET
    @Produces({MediaType.APPLICATION_JSON})
    public Book getBook(@QueryParam("id")final int BookId){
        return bookDao.get(BookId);
    }

    @POST
    @Produces({MediaType.APPLICATION_JSON})
    public Boolean insertBook(final Book bk)
    {
        return bookDao.update(bk);
    }

    @PUT
    @Produces({MediaType.APPLICATION_JSON})
    public Boolean putBook(final Book bk){
        return bookDao.update(bk);
    }
    @DELETE
    @Produces({MediaType.APPLICATION_JSON})
    public Boolean delBook(@QueryParam(("id"))final Integer bookId){
        return bookDao.delete(bookId);
    }
}
运行后，可以通过application.wadl查看提供的REST API及调用方法。另外，REST API可以采用RestClient测试。
在设计资源类时必须注意以下几点：
1、资源类必须是public访问类型
2、资源类的构造函数也是public访问类型
3、项目文件及代码采用UTF-8格式保存，否则容易导致后面调试的乱码问题
4、用到JSON编码，需要加入JackSON依赖包
5、实体类要提供无参构造函数，否则从相应的JSON字符串无法解析出实体类