Spring in Action 5th edition Chapter 3_insert select keyholder-优快云博客

本文详细讲解了如何使用Spring JdbcTemplate进行数据库操作，包括插入、选择记录及获取自动生成的键。同时，介绍了SimpleJdbcInsert的用法，以及其与JdbcTemplate在插入操作上的对比。此外，还探讨了JDBC与JPA的区别。

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Chapter 3

Core Questions

How to use JdbcTemplate
- insert
- select
How to use SimpleJdbcInsert
How to get the generated key
- using JdbcTemplate
- using SimpleJdbcInsert
What is the difference between JDBC and JPA.

How to use `JdbcTemplate`

@Repository
public MyRepository implements SomeRepoInterface {
  private final JdbcTemplate jdbc;
  @Autowired
  public MyRepository(JdbcTemplate jdbc) {
    this.jdbc = jdbc;
  }
  
  //select use query() method
  public List<MyObject> findAll() {
    return jdbc.query("select * from table", 
                      (rs, i) -> /*code to map to the target class*/);
  }
  
  //insert use update() method
  public MyObject save(MyObject myObject) {
    jdbc.update("insert into table(...) values (?, ...)",
              myObject.get..(),
              myObject.get..(), ...);
    return myObject;
  }
  
  //insert and get generated key
  public long save(MyObject myObject) {
    
    PreparedStatementCreator psc;
    KeyHolder keyHolder;
    
    psc = new PreparedStatementCreatorFactory(
      "insert into ...", Types.SOMETYPE, .../*define the types*/)
      .newPreparedStatementCreator(Arrays.asList(.../*values go here*/));
    keyHolder = new GeneratedKeyHolder();
    
    jdbc.update(psc, keyHolder);
    
    return keyHolder.getKey().longValue(); //getKey() method returns Number type.
  }
}

How to use `SimpleJdbcInsert`

@Repository
public class MyRepository implements MyRepoInterface {
  
  private final JdbcTemplate jdbc;
  private final SimpleJdbcInserter inserter;
  private final ObjectMapper mapper;
  
  @Autowired
  public MyRepository(JdbcTemplate jdbc) {
    this.jdbc = jdbc;
    this.inserter = new SimpleJdbcInserter()
      .withTableName("MyTable")
      .usingColumns("Column1", ...)
      .usingGeneratedKeyColumns("Column 1", ...);
    this.mapper = new ObjectMapper();
  }
  
  //insert and get the key
  public long save(MyObject myObject) {
    Map<String, Object> values = mapper.convertValue(myObject, Map.class);
    values.put(..., ...); //for some fields may not be converted 
    ...
    return inserter.executeAndReturnKey(values).longValue();
  }      
}