JDBC--使用beanutils工具类操作JavaBean

1、在JavaEE中，Java类的属性通过getter,setter来定义；

2、可使用BeanUtils工具包来操作Java类的属性：

--Beanutils是由Apache公司开发，能够方便对Bean类进行简便的操作

--涉及到的包：

(1)   BeanUtils相关包

commons-beanutils-1.8.3.jar

commons-beanutils-1.8.3-javadoc.jar

commons-beanutils-1.8.3-javadoc.jar

commons-beanutils-bean-collections-1.8.3.jar

commons-beanutils-core-1.8.3.jar

(2)   Logic4j相关包

commons-logging.jar

3、使用举例：

Bean类Customer:

public class Customer {

    private int id;
    private String name;
    private Date birth;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Date getBirth() {
        return birth;
    }

    public void setBirth(Date birth) {
        this.birth = birth;
    }

    public Customer(int id, String name, Date birth) {
        super();
        this.id = id;
        this.name = name;
        this.birth = birth;
    }

    public Customer() {
    }
}

使用BeanUtils的setProperty()和getProperty()方法设置和获取属性：

public void testBeanUtils() throws Exception{
    Customer customer = new Customer();
    //设置customer的name属性
    BeanUtils.setProperty(customer, "name", "Bob");
    System.out.println(customer);
    //获取customer的属性值
    String name = (String)BeanUtils.getProperty(customer, "name");
    System.out.println(name);
}

4、在JDBC中，当我们在编写DAO中的通用方法来进行查询时，可以使用BeanUtils类来为属性赋值（第32行）：

public <T> T get(Class<T> clazz, String sql, Object ...args){
    T entity = null;
    Connection conn = null;
    PreparedStatement ps = null;
    ResultSet rs = null;
    try{
        conn = DAO.getConnection();
        ps = conn.prepareStatement(sql);
        for(int i = 0; i < args.length; i++){
            ps.setObject(i + 1, args[i]);
        }
        
        rs = ps.executeQuery();
        Map<String, Object> map = new HashMap<String, Object>();
        ResultSetMetaData rsmd = rs.getMetaData();
        
        if(rs.next()){
            for(int i = 0; i < rsmd.getColumnCount(); i++){
                String columnLabel = rsmd.getColumnLabel(i + 1);
                Object columnValue = rs.getObject(columnLabel);
            
                map.put(columnLabel, columnValue);
            }
        }
        
        if(map.size() > 0){
            entity = clazz.newInstance();
            for(Map.Entry<String, Object> entry : map.entrySet()){
                String fieldName = entry.getKey();
                Object value = entry.getValue();
                //使用BeanUtils工具类来为属性赋值
                BeanUtils.setProperty(entity, fieldName, value);
                /**使用反射的方式为属性赋值
                Field field = clazz.getDeclaredField(key);
                field.setAccessible(true);
                field.set(entity, value);*/
            }
            return entity;
        }
        
    }catch(Exception e){
        e.printStackTrace();
    }finally{
        if(rs != null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(ps != null){
            try {
                ps.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(conn != null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    return entity;
}