SpringBoot之控制器的返回值處理方式

更新時間：2023年07月19日 08:37:07 作者：yyangqqian

這篇文章主要介紹了SpringBoot之控制器的返回值處理方式，具有很好的參考價值，希望對大家有所幫助。如有錯誤或未考慮完全的地方，望不吝賜教

SpringBoot控制器的返回值處理

@Controller：默認返回值是視圖名稱，如果需要返回Json字符串，需要在方法上加@ResponseBody注解，默認使用 Jackson 框架處理。
@RestController：是@ResponseBody和@Controller的組合注解。

Spring Boot 中默認使用的 Json 解析框架是 Jackson 。

在實際項目中，難免會遇到一些 null 值出現(xiàn)，在轉(zhuǎn) Json 時，是不希望有這些 null 出現(xiàn)的。

比如期望所有的 null 在轉(zhuǎn) Json 時都變成 “” 這種空字符串。

在 Spring Boot 中，做一下配置即可，新建一個 Jackson 的配置類：

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
import java.io.IOException;
@Configuration
public class JacksonConfig {
    @Bean
    @Primary
    @ConditionalOnMissingBean(ObjectMapper.class)
    public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) {
        ObjectMapper objectMapper = builder.createXmlMapper(false).build();
        objectMapper.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>() {
            @Override
            public void serialize(Object o, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
                jsonGenerator.writeString("");
            }
        });
        return objectMapper;
    }
}

SpringBoot 啟用Fastjson轉(zhuǎn)換

fastJson依賴導(dǎo)入：

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.35</version>
</dependency>

SpringBoot 啟用Fastjson轉(zhuǎn)換，需要繼承WebMvcConfigurerAdapter，并重寫configureMessageConverters方法。

import com.alibaba.fastjson.serializer.SerializerFeature;
import com.alibaba.fastjson.support.config.FastJsonConfig;
import com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;
@Configuration
public class FastJWebMvcConfigurer extends WebMvcConfigurationSupport {
    /***
     * 使用阿里 FastJson 作為JSON MessageConverter
     * @param converters
     * */
    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();
        FastJsonConfig config = new FastJsonConfig();
        config.setSerializerFeatures(
                // 保留map空的字段
                SerializerFeature.WriteMapNullValue,
                // 將String類型的null轉(zhuǎn)成""
                SerializerFeature.WriteNullStringAsEmpty,
                // 將Number類型的null轉(zhuǎn)成0
                SerializerFeature.WriteNullNumberAsZero,
                // 將List類型的null轉(zhuǎn)成[]
                SerializerFeature.WriteNullListAsEmpty,
                // 將Boolean類型的null轉(zhuǎn)成false
                SerializerFeature.WriteNullBooleanAsFalse,
                // 避免循環(huán)引用
                SerializerFeature.DisableCircularReferenceDetect);
        // converter.setFastJsonConfig(config);
        converter.setDefaultCharset(Charset.forName("UTF-8"));
        List<MediaType> mediaTypeList = new ArrayList<>();
        // 解決中文亂碼問題，相當(dāng)于在Controller上的@RequestMapping中加了個屬性produces = "application/json"
        mediaTypeList.add(MediaType.APPLICATION_JSON);
        converter.setSupportedMediaTypes(mediaTypeList);
        converters.add(converter);
    }
}

SpringBoot控制器返回值-中文亂碼問題

@RequestMapping 注解增加produces屬性解決中文亂碼問題

@RequestMapping(value="/create/index",produces = "application/json;charset=utf-8")
public ResponseBean createIndex(@RequestParam String indexName)
        {
        try {
        XContentBuilder builder = XContentFactory.jsonBuilder()
        .startObject()
        .field("properties")
        .startObject()
        .field("name").startObject().field("index", "true").field("type", "keyword").endObject()
        .field("age").startObject().field("index", "true").field("type", "integer").endObject()
        .field("money").startObject().field("index", "true").field("type", "double").endObject()
        .field("address").startObject().field("index", "true").field("type", "text").endObject()
        .field("birthday").startObject().field("index", "true").field("type", "date").endObject()
//.field("address").startObject().field("index", "true").field("type", "text").field("analyzer", "ik_max_word").endObject()
//.field("birthday").startObject().field("index", "true").field("type", "date").field("format", "strict_date_optional_time||epoch_millis").endObject()
        .endObject()
        .endObject();
        CreateIndexRequest createIndexRequest = new CreateIndexRequest(indexName);
        createIndexRequest.mapping(indexName,builder);
        CreateIndexResponse createIndexResponse = client.indices().create(createIndexRequest, RequestOptions.DEFAULT);
        boolean acknowledged = createIndexResponse.isAcknowledged();
        if (acknowledged) {
        return new ResponseBean(200, "創(chuàng)建成功", null);
        } else {
        return new ResponseBean(1002, "創(chuàng)建失敗", null);
        }
        } catch (IOException e) {
        e.printStackTrace();
        }catch (ElasticsearchStatusException e)
        {
        logger.info("創(chuàng)建失敗---索引已經(jīng)存在");
        return new ResponseBean(1002, "創(chuàng)建失敗---索引已經(jīng)存在", null);
        }
        return null;
        }