springJDBC和SpringJDBCTemplate解决方案探究

先来看一个纯JDBC的例子，体会一下springJDBC和SpringJDBCTemplate两者的区别

一个Customer类

 package com.mkyong.customer.model;

 import java.sql.Timestamp;

 public class Customer
 {
     int custId;
     String name;
     int age;

     public Customer(int custId, String name, int age) {
         this.custId = custId;
         this.name = name;
         this.age = age;
     }

     public int getCustId() {
         return custId;
     }
     public void setCustId(int custId) {
         this.custId = custId;
     }
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     public int getAge() {
         return age;
     }
     public void setAge(int age) {
         this.age = age;
     }

     @Override
     public String toString() {
         return "Customer [age=" + age + ", custId=" + custId + ", name=" + name
                 + "]";
     }

 }

Dao类：

 package com.mkyong.customer.dao;

 import com.mkyong.customer.model.Customer;

 public interface CustomerDAO
 {
     public void insert(Customer customer);
     public Customer findByCustomerId(int custId);
 }

DaoImpl类：

 package com.mkyong.customer.dao.impl;

 import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;

 import javax.sql.DataSource;

 import com.mkyong.customer.dao.CustomerDAO;
 import com.mkyong.customer.model.Customer;

 public class JdbcCustomerDAO implements CustomerDAO
 {
     private DataSource dataSource;

     public void setDataSource(DataSource dataSource) {
         this.dataSource = dataSource;
     }

     public void insert(Customer customer){

         String sql = "INSERT INTO CUSTOMER " +
                 "(CUST_ID, NAME, AGE) VALUES (?, ?, ?)";
         Connection conn = null;   //每次都要重新声明一个conection

         try {
             conn = dataSource.getConnection();
             PreparedStatement ps = conn.prepareStatement(sql);   //每次都要进行conn.prepareStatment操作
             ps.setInt(, customer.getCustId());
             ps.setString(, customer.getName());
             ps.setInt(, customer.getAge());
             ps.executeUpdate();  //每次都要提交更新
             ps.close();  //每次都要手动关闭数据库连接

         } catch (SQLException e) {   //每次都要进行异常处理。导致大量冗余的代码
             throw new RuntimeException(e);

         } finally {
             if (conn != null) {
                 try {
                     conn.close();
                 } catch (SQLException e) {}
             }
         }
     }

     public Customer findByCustomerId(int custId){

         String sql = "SELECT * FROM CUSTOMER WHERE CUST_ID = ?";

         Connection conn = null;

         try {
             conn = dataSource.getConnection();
             PreparedStatement ps = conn.prepareStatement(sql);
             ps.setInt(, custId);
             Customer customer = null;
             ResultSet rs = ps.executeQuery();
             if (rs.next()) {
                 customer = new Customer(
                         rs.getInt("CUST_ID"),
                         rs.getString("NAME"),
                         rs.getInt("Age")
                 );
             }
             rs.close();
             ps.close();
             return customer;
         } catch (SQLException e) {
             throw new RuntimeException(e);
         } finally {
             if (conn != null) {
                 try {
                 conn.close();
                 } catch (SQLException e) {}
             }
         }
     }
 }

上述的例子充满了大量的冗余代码。，CRUD操作都要对应的写：

conn.open(); conn.prepareStatment(); conn.close() 以及异常处理....等等

这样子显得非常多余，可以有更加优雅的解决方案吗？   废话当然有，Look~↓

提供了JdbcTemplate 来封装数据库jdbc操作细节： 
包括： 数据库连接[打开/关闭] ，异常转义 ，SQL执行 ，查询结果的转换

使用模板方式封装 jdbc数据库操作-固定流程的动作，提供丰富callback回调接口功能，方便用户自定义加工细节，更好模块化jdbc操作，简化传统的JDBC操作的复杂和繁琐过程。

看下面代码：

 package com.mkyong.customer.dao.impl;

 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;

 import org.springframework.jdbc.core.namedparam.BeanPropertySqlParameterSource;
 import org.springframework.jdbc.core.namedparam.SqlParameterSource;
 import org.springframework.jdbc.core.namedparam.SqlParameterSourceUtils;
 import org.springframework.jdbc.core.simple.ParameterizedBeanPropertyRowMapper;
 import org.springframework.jdbc.core.simple.SimpleJdbcDaoSupport;

 import com.mkyong.customer.dao.CustomerDAO;
 import com.mkyong.customer.model.Customer;
 import com.mkyong.customer.model.CustomerParameterizedRowMapper;

 public class SimpleJdbcCustomerDAO extends SimpleJdbcDaoSupport implements CustomerDAO
 {
     //insert example
     public void insert(Customer customer){

         String sql = "INSERT INTO CUSTOMER " +
             "(CUST_ID, NAME, AGE) VALUES (?, ?, ?)";

         getSimpleJdbcTemplate().update(sql, customer.getCustId(),
                     customer.getName(),customer.getAge()
         );

     }

     //insert with named parameter
     public void insertNamedParameter(Customer customer){

         String sql = "INSERT INTO CUSTOMER " +
             "(CUST_ID, NAME, AGE) VALUES (:custId, :name, :age)";

         Map<String, Object> parameters = new HashMap<String, Object>();
         parameters.put("custId", customer.getCustId());
         parameters.put("name", customer.getName());
         parameters.put("age", customer.getAge());

         getSimpleJdbcTemplate().update(sql, parameters);

     }

     //insert batch example
     public void insertBatch(final List<Customer> customers){

         String sql = "INSERT INTO CUSTOMER " +
             "(CUST_ID, NAME, AGE) VALUES (?, ?, ?)";

         List<Object[]> parameters = new ArrayList<Object[]>();
         for (Customer cust : customers) {
             parameters.add(new Object[] {cust.getCustId(), cust.getName(), cust.getAge()});
         }
         getSimpleJdbcTemplate().batchUpdate(sql, parameters);

     }

     //insert batch with named parameter
     public void insertBatchNamedParameter(final List<Customer> customers){

         String sql = "INSERT INTO CUSTOMER " +
             "(CUST_ID, NAME, AGE) VALUES (:custId, :name, :age)";

         List<SqlParameterSource> parameters = new ArrayList<SqlParameterSource>();
         for (Customer cust : customers) {

             parameters.add(new BeanPropertySqlParameterSource(cust));

         }
         getSimpleJdbcTemplate().batchUpdate(sql,
                 parameters.toArray(new SqlParameterSource[]));
     }

     //insert batch with named parameter
     public void insertBatchNamedParameter2(final List<Customer> customers){

         SqlParameterSource[] params = SqlParameterSourceUtils.createBatch(customers.toArray());
         getSimpleJdbcTemplate().batchUpdate(
                 "INSERT INTO CUSTOMER (CUST_ID, NAME, AGE) VALUES (:custId, :name, :age)",
                 params);

     }

     //insert batch example with SQL
     public void insertBatchSQL(final String sql){

         getJdbcTemplate().batchUpdate(new String[]{sql});

     }

     //query single row with ParameterizedRowMapper
     public Customer findByCustomerId(int custId){

         String sql = "SELECT * FROM CUSTOMER WHERE CUST_ID = ?";

         Customer customer = getSimpleJdbcTemplate().queryForObject(
                 sql,  new CustomerParameterizedRowMapper(), custId);

         return customer;
     }

     //query single row with ParameterizedBeanPropertyRowMapper (Customer.class)
     public Customer findByCustomerId2(int custId){

         String sql = "SELECT * FROM CUSTOMER WHERE CUST_ID = ?";

         Customer customer = getSimpleJdbcTemplate().queryForObject(
                 sql,ParameterizedBeanPropertyRowMapper.newInstance(Customer.class), custId);

         return customer;
     }

     //query mutiple rows with ParameterizedBeanPropertyRowMapper (Customer.class)
     public List<Customer> findAll(){

         String sql = "SELECT * FROM CUSTOMER";

         List<Customer> customers =
             getSimpleJdbcTemplate().query(sql, ParameterizedBeanPropertyRowMapper.newInstance(Customer.class));

         return customers;
     }

     //query mutiple rows with ParameterizedBeanPropertyRowMapper (Customer.class)
     public List<Customer> findAll2(){

         String sql = "SELECT * FROM CUSTOMER";

         List<Customer> customers =
             getSimpleJdbcTemplate().query(sql, ParameterizedBeanPropertyRowMapper.newInstance(Customer.class));

         return customers;
     }

     public String findCustomerNameById(int custId){

         String sql = "SELECT NAME FROM CUSTOMER WHERE CUST_ID = ?";

         String name = getSimpleJdbcTemplate().queryForObject(
                 sql, String.class, custId);

         return name;

     }

     public int findTotalCustomer(){

         String sql = "SELECT COUNT(*) FROM CUSTOMER";

         int total = getSimpleJdbcTemplate().queryForInt(sql);

         return total;
     }

 }

细心你，会发现JdbcTemplate的实例中有一系列的方法如：queryForXXX,update,delete大大简化了JDBC操作。

当然,还可以再进一步的优化一下,就是通过依赖注入，直接把jdbcTemplate注入到dao类的jdbcT字段。

快动手试试吧！  提示：Spring还提供了和Hibernate整合的SpringHibernateTemplate解决方案哦。