Converting a JDBC ResultSet to JSON in Java

How to Convert a JDBC ResultSet to JSON in Java

Java Database Connectivity (JDBC) is an application programming interface (API) for the programming language Java, which defines how a client may access a database. It provides methods for querying and updating data in a database. The JDBC API includes a ResultSet object, which is a representation of the data returned from a query. In this tutorial, we'll discuss how to convert a ResultSet to JSON in Java.

1. Overview

The ResultSet object is a container for the rows of data returned from a query. It has methods for iterating through the rows, accessing individual fields, and retrieving specific types of data. However, the data is still in its tabular form, and in order to use the data within a web application, you may need to convert the ResultSet into JSON.

2. Using the JSON-P Library

The JSON Processing (JSON-P) library, which is part of Java EE 7, makes it easy to convert a ResultSet into JSON. It provides a JsonObjectBuilder class, which can be used to create a JsonObject instance from a ResultSet. The following example shows how to use this class:

try ( Connection connection = DriverManager.getConnection( url ); 
      Statement stmt = connection.createStatement(); 
      ResultSet rs = stmt.executeQuery( "SELECT * FROM table" ); ) { 
 
  JsonObject jsonObject = Json.createObjectBuilder() 
    .add("results", Json.createArrayBuilder() 
      .add(rs)) 
    .build(); 
 
} catch (SQLException e) { 
  // handle the exception 
}

The above example creates a JsonObjectBuilder instance and then adds a “results” field to it. The value of this field is a JsonArrayBuilder instance, which is populated with the data from the ResultSet. This array is then used to create a JsonObject instance, which contains the data in JSON format.

3. Using Jackson

The Jackson library is another popular library for converting Java objects to JSON. It provides the ObjectMapper class which can be used to convert a ResultSet into JSON. The following example shows how to use this class:

try ( Connection connection = DriverManager.getConnection( url ); 
      Statement stmt = connection.createStatement(); 
      ResultSet rs = stmt.executeQuery( "SELECT * FROM table" ); ) { 
 
  ObjectMapper mapper = new ObjectMapper(); 
  JsonNode jsonNode = mapper.readTree(rs); 
 
} catch (SQLException e) { 
  // handle the exception 
} 

The above example first creates an ObjectMapper instance and then uses it to read the ResultSet and convert it into a JsonNode object. The JsonNode object can then be used to access the data in JSON format.

4. Conclusion

In this tutorial, we discussed how to convert a ResultSet to JSON in Java. We looked at two libraries, JSON-P and Jackson, that make it easy to convert a ResultSet into JSON. With either of these libraries, you can quickly and easily convert a ResultSet into a JSON format that is easy to use in a web application.