1. Use the default json to convert HttpessageConverter

At present, JSON is the mainstream front and back end data transmission mode. In spring MVC, HttpMessageConverter is used to support the conversion of JSON, and the relevant configuration is further simplified in spring boot.

pom.xml

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>

By default, jacjson databind is added as the JSON processor in this dependency. At this time, you can return JSON without adding additional JSON processors.

public class Book {
private String name;
private String author;

@JsonIgnore //Filter out this property
protected Float price;
@JsonFormat(pattern = "yyyy-MM-dd") //Format output this property
private Date publicationDate;

//ellipsis getter/setter

}



@RestController
public class BookController {
@GetMapping("/book")
public Book book() {
Book book = new Book();
book.setAuthor("Luo Guanzhong");
book.setName("Romance of the Three Kingdoms");
book.setPrice(30f);
book.setPublicationDate(new Date());
return book;
}
}

Result:

This is the processing method of spring boot. If you use this method, you can use annotations to ignore fields and format dates.
The mappingjackson 2httpmessageconverter provided by default in Spring implements json conversion.

2. Custom converter
In addition to Jackson databind, the common JSON processors include Gson and fastjson
2.1 use of Gson
Gson is an open-source JSON parsing framework of Google. Before using it, first remove the default Jackson databind, and then add the gson dependency.

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
</exclusion>
</exclusions>
</dependency>

<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
</dependency>

In spring boot, the automatic conversion class gsohttpmessageconverterconfiguration of Gson is provided by default, so you can use Gson directly like Jackson databind, but you need to customize HttpMessageConverter if you want to format date data during the conversion of Gson.

protected static class GsonHttpMessageConverterConfiguration {
@Bean
@ConditionalOnMissingBean
public GsonHttpMessageConverter gsonHttpMessageConverter(Gson gson) {
GsonHttpMessageConverter converter = new GsonHttpMessageConverter();
converter.setGson(gson);
return converter;
}
}

@The ConditionalOnMissingBean annotation indicates that the default GsonHttpMessageConverter will be used when there is no GsonHttpMessageConverter provided in the project, so we can write a GsonHttpMessageConverter ourselves to avoid the default without GsonHttpMessageConverter.

@Configuration
public class GsonConfig {
@Bean
GsonHttpMessageConverter gsonHttpMessageConverter() {
GsonHttpMessageConverter converter = new GsonHttpMessageConverter();
GsonBuilder builder = new GsonBuilder();
//Set up Gson Format of date when parsing
builder.setDateFormat("yyyy-MM-dd");
//Set up Gson The modifier when parsing is protected Filter out the fields of
builder.excludeFieldsWithModifiers(Modifier.PROTECTED);
//Establish Gson Object placement GsonHttpMessageConverter And return converter
Gson gson = builder.create();
converter.setGson(gson);
return converter;
}
}



public class Book {
private String name;
private String author;
protected Float price; //Fields filtered out
private Date publicationDate;
}

2.2 using fastjson
Alibaba's json parsing framework can be integrated into SpringBoot. Unlike Gson, fastjson cannot be used immediately after inheritance. Developers need to provide HttpMessageConverter before it can be used.
Similarly, remove the Jsckson databind dependency and add the fastjson dependency

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
</exclusion>
</exclusions>
</dependency>

<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.47</version>
</dependency>

Configure HttpMessageConverter of fasjson

@Configuration
public class MyFastJsonConfig {
@Bean
FastJsonHttpMessageConverter fastJsonHttpMessageConverter() {
FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();

FastJsonConfig config = new FastJsonConfig();
//Set up json Some details in parsing, date format, data coding
config.setDateFormat("yyyy-MM-dd");
config.setCharset(Charset.forName("UTF-8"));
//Are you building Json Output class name in
//Is it output? value by null Data
//Generated json Format
//Empty set output[]Rather than null
//Empty string output '' instead of null Other configuration
config.setSerializerFeatures(
SerializerFeature.WriteClassName,
SerializerFeature.WriteMapNullValue,
SerializerFeature.PrettyFormat,
SerializerFeature.WriteNullListAsEmpty,
SerializerFeature.WriteNullStringAsEmpty
);

converter.setFastJsonConfig(config);
return converter;
}
}

If the output Chinese is garbled: spring. Http. Encoding. Force response = true

There is another way to configure FastJsonHttpMessageConverter

After introducing spring boot starter web, he relies on spring boot autoconfigure. In this automatic configuration, a webmvcauautoconfiguration class provides the most basic configuration of spring MVC. If you want to configure yourself, you only need to implement the WebMvcConfigurer interface.

@Configuration
public class MyWebMvcConfig implements WebMvcConfigurer {
　　

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();

FastJsonConfig config = new FastJsonConfig();
config.setDateFormat("yyyy-MM-dd");
config.setCharset(Charset.forName("UTF-8"));
config.setSerializerFeatures(
SerializerFeature.WriteClassName,
SerializerFeature.WriteMapNullValue,
SerializerFeature.PrettyFormat,
SerializerFeature.WriteNullListAsEmpty,
SerializerFeature.WriteNullStringAsEmpty
);
converter.setFastJsonConfig(config);

converters.add(converter);
}

}