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Spring Boot (2) Restful风格接口

Rest接口

　　动态页面jsp早已过时，现在流行的是vuejs、angularjs、react等前端框架调用 rest接口（json格式），如果是单台服务器，用动态还是静态页面可能没什么大区别，如果服务器用到了集群，负载均衡，CDN等技术，用动态页面还是静态页面差别非常大。

传统rest用法

　　用spring mvc可以很容易的实现json格式的rest接口，这是比较传统的用法，在spring boot中已经自动配置了jackson。

@Controller
public class HelloController {

    @Autowired
    String hello;

    @RequestMapping(value = "/hello",method = RequestMethod.POST)
    @ResponseBody
    public String hello(User user){
        return "hello world";
    }
}

新的rest用法

　　在比较新的spring版本中，出了几个新的注解，简化了上面的用法，如下

/**
 * RestController 等价于 @Controller 和 @ResponseBody
 */
@RestController
public class HelloController {

    @PostMapping("/postUserAPI")
    public User postUserAPI(@RequestBody User user){ //@RequestBody json格式参数->自动转换为user
        return user;
    }
}

ajax调用Rest

<html>
<head>
    <title>Title</title>
    <script  src="http://libs.baidu.com/jquery/1.7.2/jquery.min.js"></script>
    <script>
        $(function(){
            var data = {
                userId:1,
                userName:'david'
            };
            $.ajax({
                url:'/dev/postUserAPI',
                type:"post",
                data:JSON.stringify(data),
                contentType:'application/json;charset=UTF-8',
                dataType:"json",
                success:function(data){
                    console.log(data)
                }
            });
        });
    </script>
</head>
<body>
index
</body>
</html>

spring boot 默认使用jackson 处理json，如果我们想要使用fast的json解析框架的话

1.我们需要在pom.xml中引入相应的依赖

        <!--fastjson数据配置-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.29</version>
        </dependency>

2.需要在SpringBootApplication启动类中配置一下，配置有两种方式：

　　1.继承WebMVCConfigurerAdapter并重写方法configureMessageConverters 添加我们自定义的json解析框架。

package com.spring.boot;

import com.alibaba.fastjson.serializer.SerializerFeature;
import com.alibaba.fastjson.support.config.FastJsonConfig;
import com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

import java.util.List;

@SpringBootApplication
public class BootApplication extends WebMvcConfigurerAdapter {

    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        super.configureMessageConverters(converters);

        //1.定义一个convert转换消息对象
        FastJsonHttpMessageConverter fastConverter=new FastJsonHttpMessageConverter();

        //2.添加fastjson的配置信息，比如：是否要格式化返回json数据
        FastJsonConfig fastJsonConfig=new FastJsonConfig();
        fastJsonConfig.setSerializerFeatures(SerializerFeature.PrettyFormat);
        fastConverter.setFastJsonConfig(fastJsonConfig);
        converters.add(fastConverter);
    }

    public static void main(String[] args) {
        SpringApplication.run(BootApplication.class, args);
    }
}

　　2.使用@Bean注入第三方的json解析器。

package com.david;

import com.alibaba.fastjson.serializer.SerializerFeature;
import com.alibaba.fastjson.support.config.FastJsonConfig;
import com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.web.HttpMessageConverters;
import org.springframework.context.annotation.Bean;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

import java.util.List;

@SpringBootApplication
public class DemoApplication{

    @Bean//使用@Bean注入fastJsonHttpMessageConvert
    public HttpMessageConverters fastJsonHttpMessageConverters(){
        //1.需要定义一个Convert转换消息的对象
        FastJsonHttpMessageConverter fastConverter=new FastJsonHttpMessageConverter();

        //2.添加fastjson的配置信息，比如是否要格式化返回的json数据
        FastJsonConfig fastJsonConfig=new FastJsonConfig();
        fastJsonConfig.setSerializerFeatures(SerializerFeature.PrettyFormat);

        //3.在convert中添加配置信息
        fastConverter.setFastJsonConfig(fastJsonConfig);

        HttpMessageConverter<?> converter=fastConverter;
        return new HttpMessageConverters(converter);
    }

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class,args);
    }
}

fastjson常用方法：

        //bean转换json
        //将对象转换成格式化的json
        JSON.toJSONString(obj, true);

        //将对象转换成非格式化的json
        JSON.toJSONString(obj, false);

        //obj设计对象
        //对于复杂类型的转换,对于重复的引用在转成json串后在json串中出现引用的字符,比如 $ref":"$[0].books[1]
        Student stu = new Student();
        Set books = new HashSet();
        Book book = new Book();
        books.add(book);
        stu.setBooks(books);

        List list = new ArrayList();
        for (int i = 0; i < 5; i++)
            list.add(stu);

        String json = JSON.toJSONString(list, true);

        //json转换bean
        String json = "{"id":"2","name":"Json技术"}";
        Book book = JSON.parseObject(json, Book.class);

        //json转换复杂的bean，比如List，Map
        String json = "[{"id":"1","name":"Json技术"},{"id":"2","name":"java技术"}]";

        //将json转换成List
        List list = JSON.parseObject(json, new TypeReference<ARRAYLIST>() {
        });

        //将json转换成Set
        Set set = JSON.parseObject(json, new TypeReference<HASHSET>() {
        });

        //通过json对象直接操作json
        //从json串中获取属性
        String propertyName = 'id';
        String propertyValue = "";
        String json = "{"id":"1","name":"Json技术"}";
        JSONObject obj = JSON.parseObject(json);
        propertyValue = obj.get(propertyName));

        //除去json中的某个属性
        String propertyName = 'id';
        String propertyValue = "";
        String json = "{"id":"1","name":"Json技术"}";
        JSONObject obj = JSON.parseObject(json);
        Set set = obj.keySet();
        propertyValue = set.remove(propertyName);
        json = obj.toString();

        //向json中添加属性
        String propertyName = 'desc';
        Object propertyValue = "json的玩意儿";
        String json = "{"id":"1","name":"Json技术"}";
        JSONObject obj = JSON.parseObject(json);
        obj.put(propertyName, JSON.toJSONString(propertyValue));
        json = obj.toString();

        //修改json中的属性
        String propertyName = 'name';
        Object propertyValue = "json的玩意儿";
        String json = "{"id":"1","name":"Json技术"}";
        JSONObject obj = JSON.parseObject(json);
        Set set = obj.keySet();
        if (set.contains(propertyName))
            obj.put(propertyName, JSON.toJSONString(propertyValue));
        json = obj.toString();

        //判断json中是否有属性
        String propertyName = 'name';
        boolean isContain = false;
        String json = "{"id":"1","name":"Json技术"}";
        JSONObject obj = JSON.parseObject(json);
        Set set = obj.keySet();
        isContain = set.contains(propertyName);

        //json中日期格式的处理
        Object obj = new Date();
        String json = JSON.toJSONStringWithDateFormat(obj, "yyyy-MM-dd HH:mm:ss.SSS");
        //使用JSON.toJSONStringWithDateFormat,该方法可以使用设置的日期格式对日期进行转换

jackson常用方法：

        //bean转换json
        //将类转换成Json,obj是普通的对象，不是List，Map的对象
        String json = JSONObject.fromObject(obj).toString();
        
        //将List，Map转换成Json
        String json = JSONArray.fromObject(list).toString();
        String json = JSONArray.fromObject(map).toString();
        
        //json转换bean
        String json = "{"id":"1","name":"Json技术"}";
        JSONObject jsonObj = JSONObject.fromObject(json);
        Book book = (Book)JSONObject.toBean(jsonObj,Book.class);
        
        //json转换List,对于复杂类型的转换会出现问题
        String json = "[{"id":"1","name":"Json技术"},{"id":"2","name":"Java技术"}]";
        JSONArray jsonArray = JSONArray.fromObject(json);
        JSONObject jsonObject;
        T bean;
        int size = jsonArray.size();
        List list = new ArrayList(size);
        for (int i = 0; i < size; i++) {
            jsonObject = jsonArray.getJSONObject(i);
            bean = (T) JSONObject.toBean(jsonObject, beanClass);
            list.add(bean);
        }
        
        //json转换Map
        String jsonString = "{"id":"1","name":"Json技术"}";
        JSONObject jsonObject = JSONObject.fromObject(jsonString);
        Iterator keyIter = jsonObject.keys();
        String key;
        Object value;
        Map valueMap = new HashMap();
        while (keyIter.hasNext()) {
            key = (String) keyIter.next();
            value = jsonObject.get(key).toString();
            valueMap.put(key, value);
        }
        
        //json对于日期的操作比较复杂，需要使用JsonConfig,比Gson和FastJson要麻烦多了
        //创建转换的接口实现类，转换成指定格式的日期
        class DateJsonValueProcessor implements JsonValueProcessor{
            public static final String DEFAULT_DATE_PATTERN = "yyyy-MM-dd HH:mm:ss.SSS";
            private DateFormat dateFormat;
            public DateJsonValueProcessor(String datePattern) {
                try {
                    dateFormat = new SimpleDateFormat(datePattern);
                } catch (Exception ex) {
                    dateFormat = new SimpleDateFormat(DEFAULT_DATE_PATTERN);
                }
            }
            public Object processArrayValue(Object value, JsonConfig jsonConfig) {
                return process(value);
            }
            public Object processObjectValue(String key, Object value,
                                             JsonConfig jsonConfig) {
                return process(value);
            }
            private Object process(Object value) {
                return dateFormat.format[1];
                Map<STRING,DATE> birthDays = new HashMap<STRING,DATE>();
                birthDays.put("WolfKing",new Date());
                JSONObject jsonObject = JSONObject.fromObject(birthDays, jsonConfig);
                String json = jsonObject.toString();
                System.out.println(json);
            }
        }
        //JsonObject 对于json的操作和处理
        
        //从json串中获取属性
        String jsonString = "{"id":"1","name":"Json技术"}";
        Object key = "name";
        Object value = null;
        JSONObject jsonObject = JSONObject.fromObject(jsonString);
        value = jsonObject.get(key);
        jsonString = jsonObject.toString();
        
        //除去json中的某个属性
        String jsonString = "{"id":"1","name":"Json技术"}";
        Object key = "name";
        Object value = null;
        JSONObject jsonObject = JSONObject.fromObject(jsonString);
        value = jsonObject.remove(key);
        jsonString = jsonObject.toString();
        
        //向json中添加和修改属性，有则修改，无则添加
        String jsonString = "{"id":"1","name":"Json技术"}";
        Object key = "desc";
        Object value = "json的好东西";
        JSONObject jsonObject = JSONObject.fromObject(jsonString);
        jsonObject.put(key,value);
        jsonString = jsonObject.toString();
        
        //判断json中是否有属性
        String jsonString = "{"id":"1","name":"Json技术"}";
        boolean containFlag = false;
        Object key = "desc";
        JSONObject jsonObject = JSONObject.fromObject(jsonString);
        containFlag = jsonObject.containsKey(key);

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原文地址：https://www.cnblogs.com/baidawei/p/9101204.html