Convert RestTemplate json to entity class

Sometimes we need to use RestTemplate to access other url resources in java server, but because it is a class in two servers (JVMs), how to transfer entity classes?

• Contract entity class
  This example returns the entity class with AgreementApproveForOA as the result
• Code to accept request

 @ApiOperation(value = "Get framework agreement")
 @PostMapping("/getAgreementApprove")
 public ResponseEntity<AgreementApproveDTO> getAgreementApprove(@RequestParam Integer fcompanyId, @RequestParam Integer fcompanyType, @RequestHeader("fuid") Integer faid) {
      return xxx;
 }

• Transformation instance

  public static AgreementApproveForOA getData() throws IOException {
        HttpHeaders headers = new HttpHeaders();
        headers.add("fuid", "2");//Set header
        String url = "http://localhost:8481/admin/admin/agreementApprove/getAgreementApprove?fcompanyId=174&fcompanyType=1";
        ResponseEntity<String> data = restTemplate.postForEntity(url, new HttpEntity<String>(headers), String.class);//Get json string
        AgreementResponseEntity agreementResponseEntity;
        //readValue(json string, which corresponds to the assembled entity class)
        agreementResponseEntity = mapper.readValue(data.getBody(), AgreementResponseEntity.class); 
        return agreementResponseEntity.getRetEntity();
    }

• Attach dependency pom.xml

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.9.5</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.10.0</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>5.1.10.RELEASE</version>
        </dependency>

• Trampled pit
  • The jackson package does not support the format of 2019-01-05 13:25:10. The following errors will occur

 Cannot deserialize value of type `java.util.Date` from String "2019-10-03 00:00:00": not a valid representation (error: Failed to parse Date value '2019-10-03 00:00:00': Cannot parse date "2019-10-03 00:00:00": while it seems to fit format 'yyyy-MM-dd'T'HH:mm:ss.SSSZ', parsing fails (leniency? null))

• Solution: custom date resolver

Jackson2ObjectMapperBuilder jackson2ObjectMapperBuilder = new Jackson2ObjectMapperBuilder();
mapper = jackson2ObjectMapperBuilder.build();
DateFormat dateFormat = mapper.getDateFormat();
mapper.setDateFormat(new MyDateFormat(dateFormat));

MyDateFormat.java

public class MyDateFormat extends DateFormat {
 
	private DateFormat dateFormat;
 
	private SimpleDateFormat format1 = new SimpleDateFormat("yyy-MM-dd HH:mm:ss");
 
	public MyDateFormat(DateFormat dateFormat) {
		this.dateFormat = dateFormat;
	}
 
	@Override
	public StringBuffer format(Date date, StringBuffer toAppendTo, FieldPosition fieldPosition) {
		return dateFormat.format(date, toAppendTo, fieldPosition);
	}
 
	@Override
	public Date parse(String source, ParsePosition pos) {
 
		Date date = null;
 
		try {
 
			date = format1.parse(source, pos);
		} catch (Exception e) {
 
			date = dateFormat.parse(source, pos);
		}
 
		return date;
	}
 
	// Mainly decoration
	@Override
	public Date parse(String source) throws ParseException {
 
		Date date = null;
 
		try {
			
			// Follow my rules first
			date = format1.parse(source);
		} catch (Exception e) {
 
			// No, then follow the original rules
			date = dateFormat.parse(source);
		}
 
		return date;
	}
 
	// The reason for decorating the clone method here is that the clone method is also useful in jackson.
	@Override
	public Object clone() {
		Object format = dateFormat.clone();
		return new MyDateFormat((DateFormat) format);
	}
}

In this way, you can turn json into the corresponding entity class.

END