JdbcTemplate学习札记_资讯

JdbcTemplate学习札记

创始人

2024-03-16 03:54:03

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JdbcTemplate学习笔记

1、使用JdbcTemplate的execute()方法执行SQL语句

Java 代码

jdbcTemplate.execute("CREATE TABLE USER (user_id integer, name varchar(100))");
jdbcTemplate.execute("CREATE TABLE USER (user_id integer, name varchar(100))");

2、如果是UPDATE或INSERT,可以用update()方法。

Java 代码

jdbcTemplate.update("INSERT INTO USER VALUES('"
+ user.getId() + "', '"
+ user.getName() + "', '"
+ user.getSex() + "', '"
+ user.getAge() + "')");
jdbcTemplate.update("INSERT INTO USER VALUES('"
+ user.getId() + "', '"
+ user.getName() + "', '"
+ user.getSex() + "', '"
+ user.getAge() + "')");

3、带参数的更新

Java代码

jdbcTemplate.update("UPDATE USER SET name = ? WHERE user_id = ?", new Object[] {name, id});
jdbcTemplate.update("UPDATE USER SET name = ? WHERE user_id = ?", new Object[] {name, id});

Java代码

jdbcTemplate.update("INSERT INTO USER VALUES(?, ?, ?, ?)", new Object[] {user.getId(), user.getName(), user.getSex(), user.getAge()});
jdbcTemplate.update("INSERT INTO USER VALUES(?, ?, ?, ?)", new Object[] {user.getId(), user.getName(), user.getSex(), user.getAge()});

4、使用JdbcTemplate进行查询时，使用queryForXXX()等方法

Java代码

int count = jdbcTemplate.queryForInt("SELECT COUNT(*) FROM USER");
int count = jdbcTemplate.queryForInt("SELECT COUNT(*) FROM USER");

Java代码

String name = (String) jdbcTemplate.queryForObject("SELECT name FROM USER WHERE user_id = ?", new Object[] {id}, java.lang.String.class);
String name = (String) jdbcTemplate.queryForObject("SELECT name FROM USER WHERE user_id = ?", new Object[] {id}, java.lang.String.class);

Java代码

List rows = jdbcTemplate.queryForList("SELECT * FROM USER");
List rows = jdbcTemplate.queryForList("SELECT * FROM USER");

Java代码

List rows = jdbcTemplate.queryForList("SELECT * FROM USER");
Iterator it = rows.iterator();
while(it.hasNext()) {
Map userMap = (Map) it.next();
System.out.print(userMap.get("user_id") + "\t");
System.out.print(userMap.get("name") + "\t");
System.out.print(userMap.get("sex") + "\t");
System.out.println(userMap.get("age") + "\t");
}
List rows = jdbcTemplate.queryForList("SELECT * FROM USER");
Iterator it = rows.iterator();
while(it.hasNext()) {
Map userMap = (Map) it.next();
System.out.print(userMap.get("user_id") + "\t");
System.out.print(userMap.get("name") + "\t");
System.out.print(userMap.get("sex") + "\t");
System.out.println(userMap.get("age") + "\t");

}

JdbcTemplate将我们使用的JDBC的流程封装起来，包括了异常的捕捉、SQL的执行、查询结果的转换等等。spring大量使用Template Method模式来封装固定流程的动作，XXXTemplate等类别都是基于这种方式的实现。

除了大量使用Template Method来封装一些底层的操作细节，spring也大量使用callback方式类回调相关类别的方法以提供JDBC相关类别的功能，使传统的JDBC的使用者也能清楚了解spring所提供的相关封装类别方法的使用。

JDBC的PreparedStatement

Java代码

final String id = user.getId();
final String name = user.getName();
final String sex = user.getSex() + "";
final int age = user.getAge();
jdbcTemplate.update("INSERT INTO USER VALUES(?, ?, ?, ?)",
new PreparedStatementSetter() {
public void setValues(PreparedStatement ps) throws SQLException {
ps.setString(1, id);
ps.setString(2, name);
ps.setString(3, sex);
ps.setInt(4, age);
}
});
final String id = user.getId();
final String name = user.getName();
final String sex = user.getSex() + "";
final int age = user.getAge();
jdbcTemplate.update("INSERT INTO USER VALUES(?, ?, ?, ?)",
new PreparedStatementSetter() {
public void setValues(PreparedStatement ps) throws SQLException {
ps.setString(1, id);
ps.setString(2, name);
ps.setString(3, sex);
ps.setInt(4, age);
}
});

Java代码

final User user = new User();
jdbcTemplate.query("SELECT * FROM USER WHERE user_id = ?",
new Object[] {id},
new RowCallbackHandler() {
public void processRow(ResultSet rs) throws SQLException {
user.setId(rs.getString("user_id"));
user.setName(rs.getString("name"));
user.setSex(rs.getString("sex").charAt(0));
user.setAge(rs.getInt("age"));
}
});
final User user = new User();
jdbcTemplate.query("SELECT * FROM USER WHERE user_id = ?",
new Object[] {id},
new RowCallbackHandler() {
public void processRow(ResultSet rs) throws SQLException {
user.setId(rs.getString("user_id"));
user.setName(rs.getString("name"));
user.setSex(rs.getString("sex").charAt(0));
user.setAge(rs.getInt("age"));
}
});

Java代码

class UserRowMapper implements RowMapper {
public Object mapRow(ResultSet rs, int index) throws SQLException {
User user = new User();
user.setId(rs.getString("user_id"));
user.setName(rs.getString("name"));
user.setSex(rs.getString("sex").charAt(0));
user.setAge(rs.getInt("age"));
return user;
}
}
public List findAllByRowMapperResultReader() {
String sql = "SELECT * FROM USER";
return jdbcTemplate.query(sql, new RowMapperResultReader(new UserRowMapper()));
}
class UserRowMapper implements RowMapper {
public Object mapRow(ResultSet rs, int index) throws SQLException {
User user = new User();
user.setId(rs.getString("user_id"));
user.setName(rs.getString("name"));
user.setSex(rs.getString("sex").charAt(0));
user.setAge(rs.getInt("age"));
return user;
}
}
public List findAllByRowMapperResultReader() {
String sql = "SELECT * FROM USER";
return jdbcTemplate.query(sql, new RowMapperResultReader(new UserRowMapper()));
}

在getUser(id)里面使用UserRowMapper

Java代码

public User getUser(final String id) throws DataAccessException {
String sql = "SELECT * FROM USER WHERE user_id=?";
final Object[] params = new Object[] { id };
List list = jdbcTemplate.query(sql, params, new RowMapperResultReader(new UserRowMapper()));
return (User) list.get(0);
}
public User getUser(final String id) throws DataAccessException {
String sql = "SELECT * FROM USER WHERE user_id=?";
final Object[] params = new Object[] { id };
List list = jdbcTemplate.query(sql, params, new RowMapperResultReader(new UserRowMapper()));
return (User) list.get(0);
}

网上收集

org.springframework.jdbc.core.PreparedStatementCreator 返回预编译SQL 不能于Object[]一起用

Java代码

public PreparedStatement createPreparedStatement(Connection con) throws SQLException {
return con.prepareStatement(sql);
}
public PreparedStatement createPreparedStatement(Connection con) throws SQLException {
return con.prepareStatement(sql);
}

1.增删改

org.springframework.jdbc.core.JdbcTemplate 类(必须指定数据源dataSource)

Java代码

template.update("insert into web_person values(?,?,?)",Object[]);
template.update("insert into web_person values(?,?,?)",Object[]);

或

Java代码

template.update("insert into web_person values(?,?,?)",new PreparedStatementSetter(){ //匿名内部类只能访问外部最终局部变量
public void setValues(PreparedStatement ps) throws SQLException {
ps.setInt(index++,3);
});
template.update("insert into web_person values(?,?,?)",new PreparedStatementSetter(){ //匿名内部类只能访问外部最终局部变量
public void setValues(PreparedStatement ps) throws SQLException {
ps.setInt(index++,3);
});
org.springframework.jdbc.core.PreparedStatementSetter //接口处理预编译SQL
public void setValues(PreparedStatement ps) throws SQLException {
ps.setInt(index++,3);
}
public void setValues(PreparedStatement ps) throws SQLException {
ps.setInt(index++,3);
}

2.查询JdbcTemplate.query(String,[Object[]/PreparedStatementSetter],RowMapper/RowCallbackHandler)

org.springframework.jdbc.core.RowMapper 记录映射接口处理结果集

Java代码

public Object mapRow(ResultSet rs, int arg1) throws SQLException { //int表当前行数
person.setId(rs.getInt("id"));
}
List template.query("select * from web_person where id=?",Object[],RowMapper);
public Object mapRow(ResultSet rs, int arg1) throws SQLException { //int表当前行数
person.setId(rs.getInt("id"));
}
List template.query("select * from web_person where id=?",Object[],RowMapper);

org.springframework.jdbc.core.RowCallbackHandler 记录回调管理器接口处理结果集

Java代码

template.query("select * from web_person where id=?",Object[],new RowCallbackHandler(){
public void processRow(ResultSet rs) throws SQLException {
person.setId(rs.getInt("id"));
});

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