@AllArgsConstructor
public class Credentials {
    private String username;
    private String password;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    @JsonIgnore
    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

@Test
public void jsonIgnoreSerialization() throws Exception {
    ObjectMapper objectMapper = new ObjectMapper();

    String serialized = objectMapper.writeValueAsString(new Credentials("user", "pass"));
    assertThat(serialized).isEqualTo("{"username":"user"}");

    Credentials credentials = objectMapper.readValue("{"username":"user","password":"pass"}", Credentials.class);
    assertThat(credentials.getUsername()).isEqualTo("user");
    assertThat(credentials.getPassword()).isEqualTo("pass");
}