spring boot开发web api应用实践（一）入门

利用Spring Boot快速搭建一个web应用，简直是太方便了。本例快速搭建一个spring mvc应用，为前端提供api请求接口，不包含web页面，数据库持久层采用默认的spring-jdbc。

一、环境准备：

1.安装maven及ide（eclipse或idea）并安装maven插件；

2.mysql或其他数据库（本例使用mysql）；

3.jdk1.8+

二、建立工程

步骤：1.编辑pom.xml文件添加spring-boot依赖

2.编写启动类（AppMain.java）

3.编写Controller路由类(LoginController.java)

4.启动测试

1.在ide里建立一个简单maven工程，编辑pom.xml文件，内容如下：

<?xml version="1.0" encoding="UTF-8"?>
<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/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>com.zweichxu.springboot</groupId>
	<artifactId>spring-boot-web</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>spring-boot-web</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.4.1.RELEASE</version>
		<relativePath/>  
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<dependency>
		<!-- 创建一个web应用，默认j2ee容器是spring boot内置的tomcat，
		     默认访问端口是8080，默认访问context-path是“/”  
		 -->
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
			<exclusions>
			    <exclusion>
			        <groupId>org.springframework.boot</groupId>
			        <artifactId>spring-boot-starter-logging</artifactId>
			    </exclusion>
			</exclusions>
		</dependency>
                
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>com.google.guava</groupId>
			<artifactId>guava</artifactId>
			<version>21.0</version>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-log4j</artifactId>
			<version>1.3.8.RELEASE</version>
		</dependency>
		<dependency>
			<groupId>org.aspectj</groupId>
			<artifactId>aspectjweaver</artifactId>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
			    <groupId>org.springframework.boot</groupId>
			    <artifactId>spring-boot-maven-plugin</artifactId>
			    <configuration>
			        <executable>true</executable> 
			    </configuration>
			</plugin>
		</plugins>
	</build>
</project>

2.建立应用启动类（AppMain.java），也是应用启动入口：

package com.zweichxu.springboot;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

/**
 *  
 * @author zweichxu
 * @date 2017年3月30日 14:12:41
 * @version 1.0
 */
@SpringBootApplication
public class AppMain {
    public static void main(String[] args){
          SpringApplication.run(AppMain.class, args);
    }
}

spring boot应用只允许惟一一个类拥有public static void main(String[] args)方法。该类最主要的是@SpringBootApplication注解，该注解是@SpringBootConfiguration、@EnableAutoConfiguration、@ComponentScan三个注解的组合。三个注解的功能，从名字上可以猜测出来，不多解释。

启动spring boot应用只需要一句代码：SpringApplication.run(AppMain.class, args);

3. 建立Controller类（LoginController.java）接收客户端请求

package com.zweichxu.springboot.controller;

import javax.annotation.Resource;
import javax.servlet.http.HttpSession;

import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

import com.zweichxu.platform.entity.BaseResp;
import com.zweichxu.platform.util.Util;
import com.zweichxu.springboot.model.User; 

@RestController
public class LoginController { 
    @RequestMapping(value="login")
    public BaseResp doLogin(@RequestParam("acct") String userName, 
                            @RequestParam("pwd") String password){
        if (Util.isEmpty(userName) || Util.isEmpty(password)){
            return BaseResp.fail(BaseResp.RET_CODE_PROTOCOL_ERROR, "用户名及密码均不能为空");
        }
       
        //do something
        User user = new User();
        user.setName("小王");
        user.setAccount(userName);
        return BaseResp.success().setRetMsg("登录成功").addProperty("loginUser", user);
    }
    
    @RequestMapping(value="logout")
    public BaseResp doLogout(){
        //do something
       
        return BaseResp.success().setRetMsg("登出成功");
    }
}

注意：所有需要通过注解自动注入的类（如LoginController类，有@RestController注解），都必须放在启动类所在的包(com.zweichxu.springboot)或子包(如com.zweichxu.springboot.controller)下面，否则需要指定扫描路径。

返回值基础类(BaseResp.java)

package com.zweichxu.platform.entity;

import java.util.HashMap;

import com.fasterxml.jackson.annotation.JsonIgnore;

/**
 * 响应信息基础类
 * 
 * @author zweichxu
 * 
 */
public class BaseResp extends HashMap<String, Object> {
    private static final long serialVersionUID = -4036551233822181281L;
     
    public BaseResp() {
        this(0, "");
    }
    
    public BaseResp(Integer retCode) {
        setRetCode(retCode);
    }
    
    public BaseResp(Integer retCode, String retMsg) {
        setRetCode(retCode);
        setRetMsg(retMsg);
    }

    public String getToken(){
        return (String) get("token");
    }

    public BaseResp setToken(String token){
        put("token", token);
        return this;
    }

    public Integer getRetCode(){
        return (Integer) get("retCode");
    }

    public BaseResp setRetCode(Integer retCode){
        put("retCode", retCode);
        return this;
    }

    public String getRetMsg(){
        return (String) get("retMsg");
    }

    public BaseResp setRetMsg(String retMsg){
        put("retMsg", retMsg);
        return this;
    }
    
    public BaseResp addProperty(String propName, Object propValue){
        put(propName, propValue);
        return this;
    }
      
    @JsonIgnore
    public boolean isFail() {
        return !(isSuccess());
    }
    
    @JsonIgnore
    public boolean isSuccess() {
        Integer retCode = getRetCode();
        return retCode != null && retCode == RETURN_SUCCESS;
    }
    
    public static BaseResp success(){
        return new BaseResp(RETURN_SUCCESS, "操作成功");
    }
    
    public static BaseResp success(String retMsg){
        BaseResp resp = success();
        resp.setRetMsg(retMsg);
        return resp;
    }
    
    public static BaseResp fail(Integer retCode, String retMsg){
        return new BaseResp(retCode, retMsg);
    }
    
    public static BaseResp fail(String retMsg){
        return new BaseResp(RETURN_FAILURE, retMsg);
    }
    
    /**操作成功*/
    public static final int RETURN_SUCCESS = 1;
    
    /**操作失败*/
    public static final int RETURN_FAILURE = 0;
    
    /**数据记录不存在：0x00001002*/
    public static final int DATA_NOT_EXIST = 0x00001002;
    
    /**返回码：协议参数错误：0x00002001*/
    public static final int RET_CODE_PROTOCOL_ERROR = 0x00002001;
}

4.启动应用：在ide上直接运行AppMain.java类，然后在浏览器地址栏访问：http://localhost:8080/login?acct=zweichxu&pwd=123，可以看到浏览器页面返回值：

至此，一个简单的web应用搭建成功。

下一篇介绍如何修改访问端口(上面浏览器图片中可以看出，我已将默认的8080端口改成了18081)，如何开启数据库访问层；

spring boot开发web api应用实践（一）入门

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