JDBC Template 简单使用

其他 2019-03-28 09:31:10 阅读次数: 0 
                                                     JdbcTemplate介绍

​ JDBC已经能够满足大部分用户最基本的需求，但是在使用JDBC时，必须自己来管理数据库资源如：获取PreparedStatement，设置SQL语句参数，关闭连接等步骤。

​ JdbcTemplate是Spring对JDBC的封装，目的是使JDBC更加易于使用。JdbcTemplate是Spring的一部分。JdbcTemplate处理了资源的建立和释放。他帮助我们避免一些常见的错误，比如忘了总要关闭连接。他运行核心的JDBC工作流，如Statement的建立和执行，而我们只需要提供SQL语句和提取结果。
Spring源码地址：https://github.com/spring-projects/spring-framework
在JdbcTemplate中执行SQL语句的方法大致分为3类：

  1. execute：可以执行所有SQL语句，一般用于执行DDL语句。
  2. update：用于执行INSERT、UPDATE、DELETE等DML语句。
  3. queryXxx：用于DQL数据查询语句。

JdbcTemplate配置连接池

org.springframework.jdbc.core.JdbcTemplate类方便执行SQL语句

  1. public JdbcTemplate(DataSource dataSource)
创建JdbcTemplate对象，方便执行SQL语句

    
    
  2. public void execute(final String sql)
execute可以执行所有SQL语句，因为没有返回值，一般用于执行DDL语句。

JdbcTemplate使用步骤

  1. 准备DruidDataSource连接池
  2. 导入依赖的jar包
    • spring-beans-4.1.2.RELEASE.jar
    • spring-core-4.1.2.RELEASE.jar
    • spring-jdbc-4.1.2.RELEASE.jar
    • spring-tx-4.1.2.RELEASE.jar
    • com.springsource.org.apache.commons.logging-1.1.1.jar
  3. 创建JdbcTemplate对象，传入Druid连接池
  4. 调用execute、update、queryXxx等方法

案例代码

public class Demo04 {
	public static void main(String[] args) {
		// 创建表的SQL语句
		String sql = "CREATE TABLE product("
				+ "pid INT PRIMARY KEY AUTO_INCREMENT,"
				+ "pname VARCHAR(20),"
				+ "price DOUBLE"
				+ ");";

	JdbcTemplate jdbcTemplate <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">JdbcTemplate</span><span class="token punctuation">(</span>DataSourceUtils<span class="token punctuation">.</span><span class="token function">getDataSource</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	jdbcTemplate<span class="token punctuation">.</span><span class="token function">execute</span><span class="token punctuation">(</span>sql<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

}

JdbcTemplate实现增删改

API介绍

org.springframework.jdbc.core.JdbcTemplate类方便执行SQL语句

  1. public int update(final String sql)
用于执行`INSERT`、`UPDATE`、`DELETE`等DML语句。

使用步骤

1.创建JdbcTemplate对象
2.编写SQL语句
3.使用JdbcTemplate对象的update方法进行增删改

案例代码

public class Demo05 {
	public static void main(String[] args) throws Exception {
//		test01();
//		test02();
//		test03();
	}

<span class="token comment">// JDBCTemplate添加数据</span>
<span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">test01</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> Exception <span class="token punctuation">{</span>
	JdbcTemplate jdbcTemplate <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">JdbcTemplate</span><span class="token punctuation">(</span>DataSourceUtils<span class="token punctuation">.</span><span class="token function">getDataSource</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	
	String sql <span class="token operator">=</span> <span class="token string">"INSERT INTO product VALUES (NULL, ?, ?);"</span><span class="token punctuation">;</span>
	
	jdbcTemplate<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span>sql<span class="token punctuation">,</span> <span class="token string">"iPhone3GS"</span><span class="token punctuation">,</span> <span class="token number">3333</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	jdbcTemplate<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span>sql<span class="token punctuation">,</span> <span class="token string">"iPhone4"</span><span class="token punctuation">,</span> <span class="token number">5000</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	jdbcTemplate<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span>sql<span class="token punctuation">,</span> <span class="token string">"iPhone4S"</span><span class="token punctuation">,</span> <span class="token number">5001</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	jdbcTemplate<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span>sql<span class="token punctuation">,</span> <span class="token string">"iPhone5"</span><span class="token punctuation">,</span> <span class="token number">5555</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	jdbcTemplate<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span>sql<span class="token punctuation">,</span> <span class="token string">"iPhone5C"</span><span class="token punctuation">,</span> <span class="token number">3888</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	jdbcTemplate<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span>sql<span class="token punctuation">,</span> <span class="token string">"iPhone5S"</span><span class="token punctuation">,</span> <span class="token number">5666</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	jdbcTemplate<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span>sql<span class="token punctuation">,</span> <span class="token string">"iPhone6"</span><span class="token punctuation">,</span> <span class="token number">6666</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	jdbcTemplate<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span>sql<span class="token punctuation">,</span> <span class="token string">"iPhone6S"</span><span class="token punctuation">,</span> <span class="token number">7000</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	jdbcTemplate<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span>sql<span class="token punctuation">,</span> <span class="token string">"iPhone6SP"</span><span class="token punctuation">,</span> <span class="token number">7777</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	jdbcTemplate<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span>sql<span class="token punctuation">,</span> <span class="token string">"iPhoneX"</span><span class="token punctuation">,</span> <span class="token number">8888</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token comment">// JDBCTemplate修改数据</span>
<span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">test02</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> Exception <span class="token punctuation">{</span>
	JdbcTemplate jdbcTemplate <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">JdbcTemplate</span><span class="token punctuation">(</span>DataSourceUtils<span class="token punctuation">.</span><span class="token function">getDataSource</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	
	String sql <span class="token operator">=</span> <span class="token string">"UPDATE product SET pname=?, price=? WHERE pid=?;"</span><span class="token punctuation">;</span>
	
	<span class="token keyword">int</span> i <span class="token operator">=</span> jdbcTemplate<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span>sql<span class="token punctuation">,</span> <span class="token string">"XVIII"</span><span class="token punctuation">,</span> <span class="token number">18888</span><span class="token punctuation">,</span> <span class="token number">10</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"影响的行数: "</span> <span class="token operator">+</span> i<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token comment">// JDBCTemplate删除数据</span>
<span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">test03</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> Exception <span class="token punctuation">{</span>
	JdbcTemplate jdbcTemplate <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">JdbcTemplate</span><span class="token punctuation">(</span>DataSourceUtils<span class="token punctuation">.</span><span class="token function">getDataSource</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	String sql <span class="token operator">=</span> <span class="token string">"DELETE FROM product WHERE pid=?;"</span><span class="token punctuation">;</span>
	<span class="token keyword">int</span> i <span class="token operator">=</span> jdbcTemplate<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span>sql<span class="token punctuation">,</span> <span class="token number">7</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"影响的行数: "</span> <span class="token operator">+</span> i<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

}

JdbcTemplate查询-queryForInt返回一个int整数

org.springframework.jdbc.core.JdbcTemplate类方便执行SQL语句

API介绍

public int queryForInt(String sql)
执行查询语句，返回一个int类型的值。

使用步骤

  1. 创建JdbcTemplate对象
  2. 编写查询的SQL语句
  3. 使用JdbcTemplate对象的queryForInt方法
  4. 输出结果

案例代码

// queryForInt返回一个整数
public static void test01() throws Exception {
   // String sql = "SELECT COUNT(*) FROM product;";
   String sql = "SELECT pid FROM product WHERE price=18888;";
   JdbcTemplate jdbcTemplate = new JdbcTemplate(DataSourceUtils.getDataSource());
   int forInt = jdbcTemplate.queryForInt(sql);
   System.out.println(forInt);
}

JdbcTemplate查询-queryForLong返回一个long整数

讲解

org.springframework.jdbc.core.JdbcTemplate类方便执行SQL语句

API介绍

public long queryForLong(String sql)
执行查询语句，返回一个long类型的数据。

使用步骤

  1. 创建JdbcTemplate对象
  2. 编写查询的SQL语句
  3. 使用JdbcTemplate对象的queryForLong方法
  4. 输出结果

案例代码

// queryForLong  返回一个long类型整数
public static void test02() throws Exception {
   String sql = "SELECT COUNT(*) FROM product;";
   // String sql = "SELECT pid FROM product WHERE price=18888;";
   JdbcTemplate jdbcTemplate = new JdbcTemplate(DataSourceUtils.getDataSource());
   long forLong = jdbcTemplate.queryForLong(sql);
   System.out.println(forLong);
}

JdbcTemplate查询-queryForObject返回String

讲解

org.springframework.jdbc.core.JdbcTemplate类方便执行SQL语句

API介绍

public <T> T queryForObject(String sql, Class<T> requiredType)
执行查询语句，返回一个指定类型的数据。

使用步骤

  1. 创建JdbcTemplate对象
  2. 编写查询的SQL语句
  3. 使用JdbcTemplate对象的queryForObject方法，并传入需要返回的数据的类型
  4. 输出结果

案例代码

public static void test03() throws Exception {
   String sql = "SELECT pname FROM product WHERE price=7777;";
   JdbcTemplate jdbcTemplate = new JdbcTemplate(DataSourceUtils.getDataSource());
   String str = jdbcTemplate.queryForObject(sql, String.class);
   System.out.println(str);
}

JdbcTemplate查询-queryForMap返回一个Map集合

API介绍

public Map<String, Object> queryForMap(String sql)
执行查询语句，将一条记录放到一个Map中。

使用步骤

  1. 创建JdbcTemplate对象
  2. 编写查询的SQL语句
  3. 使用JdbcTemplate对象的queryForMap方法
  4. 处理结果
public static void test04() throws Exception {
   String sql = "SELECT * FROM product WHERE pid=?;";
   JdbcTemplate jdbcTemplate = new JdbcTemplate(DataSourceUtils.getDataSource());
   Map<String, Object> map = jdbcTemplate.queryForMap(sql, 6);
   System.out.println(map);
}

JdbcTemplate查询-queryForList返回一个List集合

目标

能够掌握JdbcTemplate中queryForList方法的使用

讲解

org.springframework.jdbc.core.JdbcTemplate类方便执行SQL语句

API介绍

public List<Map<String, Object>> queryForList(String sql)
执行查询语句，返回一个List集合，List中存放的是Map类型的数据。

使用步骤

  1. 创建JdbcTemplate对象
  2. 编写查询的SQL语句
  3. 使用JdbcTemplate对象的queryForList方法
  4. 处理结果
public static void test05() throws Exception {
   String sql = "SELECT * FROM product WHERE pid<?;";
   JdbcTemplate jdbcTemplate = new JdbcTemplate(DataSourceUtils.getDataSource());
   List<Map<String, Object>> list = jdbcTemplate.queryForList(sql, 8);
   for (Map<String, Object> map : list) {
      System.out.println(map);
   }
}

queryForList方法的作用？将返回的一条记录保存在Map集合中，多条记录对应多个Map，多个Map存储到List集合中

JdbcTemplate查询-RowMapper返回自定义对象

org.springframework.jdbc.core.JdbcTemplate类方便执行SQL语句

API介绍

public <T> List<T> query(String sql, RowMapper<T> rowMapper)
执行查询语句，返回一个List集合，List中存放的是RowMapper指定类型的数据。

使用步骤

  1. 定义Product类
  2. 创建JdbcTemplate对象
  3. 编写查询的SQL语句
  4. 使用JdbcTemplate对象的query方法，并传入RowMapper匿名内部类
  5. 在匿名内部类中将结果集中的一行记录转成一个Product对象

案例代码

// query使用rowMap做映射返回一个对象
public static void test06() throws Exception {
    JdbcTemplate jdbcTemplate = new JdbcTemplate(DataSourceUtils.getDataSource());

// 查询数据的SQL语句
String sql = “SELECT * FROM product;”;

List<Product> query = jdbcTemplate.query(sql, new RowMapper<Product>() {
@Override
public Product mapRow(ResultSet arg0, int arg1) throws SQLException {
Product p = new Product();
p.setPid(arg0.getInt(“pid”));
p.setPname(arg0.getString(“pname”));
p.setPrice(arg0.getDouble(“price”));
return p;
}
});

for (Product product : query) {
System.out.println(product);
}
}

  1. 使用JdbcTemplate对象的query方法，并传入RowMapper匿名内部类
  2. 在匿名内部类中将结果集中的一行记录转成一个Product对象

JdbcTemplate查询-BeanPropertyRowMapper返回自定义对象

org.springframework.jdbc.core.JdbcTemplate类方便执行SQL语句

API介绍

public <T> List<T> query(String sql, RowMapper<T> rowMapper)
执行查询语句，返回一个List集合，List中存放的是RowMapper指定类型的数据。

  
  
public class BeanPropertyRowMapper<T> implements RowMapper<T>
BeanPropertyRowMapper类实现了RowMapper接口

使用步骤

  1. 定义Product类
  2. 创建JdbcTemplate对象
  3. 编写查询的SQL语句
  4. 使用JdbcTemplate对象的query方法，并传入BeanPropertyRowMapper对象
// query使用BeanPropertyRowMapper做映射返回对象
public static void test07() throws Exception {
	JdbcTemplate jdbcTemplate = new JdbcTemplate(DataSourceUtils.getDataSource());

<span class="token comment">// 查询数据的SQL语句</span>
String sql <span class="token operator">=</span> <span class="token string">"SELECT * FROM product;"</span><span class="token punctuation">;</span>
List<span class="token generics function"><span class="token punctuation">&lt;</span>Product<span class="token punctuation">&gt;</span></span> list <span class="token operator">=</span> jdbcTemplate<span class="token punctuation">.</span><span class="token function">query</span><span class="token punctuation">(</span>sql<span class="token punctuation">,</span> <span class="token keyword">new</span> <span class="token class-name">BeanPropertyRowMapper</span><span class="token operator">&lt;</span><span class="token operator">&gt;</span><span class="token punctuation">(</span>Product<span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token keyword">for</span> <span class="token punctuation">(</span>Product product <span class="token operator">:</span> list<span class="token punctuation">)</span> <span class="token punctuation">{</span>
	System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>product<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

}

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