模拟Hibernate动态生成SQL语句

Posted 2020-08-27 kuillldan

这里有一个xml配置文件，也就是Hibernate框架中会用到的POJO和数据库的映射文件

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 3 "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
 4 <!-- 
 5     Mapping file autogenerated by MyEclipse Persistence Tools
 6 -->
 7 <hibernate-mapping>
 8     <class name="hp.pojo.Member" table="member" catalog="hedb">
 9         <id name="mid" type="java.lang.String">
10             <column name="mid" length="50" />
11             <generator class="assigned"></generator>
12         </id>
13         <property name="name" type="java.lang.String">
14             <column name="name" length="50" />
15         </property>
16         <property name="age" type="java.lang.Integer">
17             <column name="age" />
18         </property>
19         <property name="salary" type="java.lang.Double">
20             <column name="salary" precision="22" scale="0" />
21         </property>
22         <property name="birthday" type="java.util.Date">
23             <column name="birthday" length="0" />
24         </property>
25         <property name="note" type="java.lang.String">
26             <column name="note" length="65535" />
27         </property>
28     </class>
29 </hibernate-mapping>

POJO类如下:

  1 package hp.pojo;
  2 
  3 import java.util.Date;
  4 
  5 /**
  6  * Member entity. @author MyEclipse Persistence Tools
  7  */
  8 
  9 @SuppressWarnings("serial")
 10 public class Member implements java.io.Serializable
 11 {
 12 
 13     // Fields
 14 
 15     private String mid;
 16     private String name;
 17     private Integer age;
 18     private Double salary;
 19     private Date birthday;
 20     private String note;
 21 
 22     // Constructors
 23 
 24     /** default constructor */
 25     public Member()
 26     {
 27     }
 28 
 29     /** minimal constructor */
 30     public Member(String mid)
 31     {
 32         this.mid = mid;
 33     }
 34 
 35     /** full constructor */
 36     public Member(String mid, String name, Integer age, Double salary, Date birthday, String note)
 37     {
 38         this.mid = mid;
 39         this.name = name;
 40         this.age = age;
 41         this.salary = salary;
 42         this.birthday = birthday;
 43         this.note = note;
 44     }
 45 
 46     // Property accessors
 47 
 48     public String getMid()
 49     {
 50         return this.mid;
 51     }
 52 
 53     public void setMid(String mid)
 54     {
 55         this.mid = mid;
 56     }
 57 
 58     public String getName()
 59     {
 60         return this.name;
 61     }
 62 
 63     public void setName(String name)
 64     {
 65         this.name = name;
 66     }
 67 
 68     public Integer getAge()
 69     {
 70         return this.age;
 71     }
 72 
 73     public void setAge(Integer age)
 74     {
 75         this.age = age;
 76     }
 77 
 78     public Double getSalary()
 79     {
 80         return this.salary;
 81     }
 82 
 83     public void setSalary(Double salary)
 84     {
 85         this.salary = salary;
 86     }
 87 
 88     public Date getBirthday()
 89     {
 90         return this.birthday;
 91     }
 92 
 93     public void setBirthday(Date birthday)
 94     {
 95         this.birthday = birthday;
 96     }
 97 
 98     public String getNote()
 99     {
100         return this.note;
101     }
102 
103     public void setNote(String note)
104     {
105         this.note = note;
106     }
107 
108 }

下面代码演示了利用反射以及XML解析，动态生成SQL语句，并且利用JDBC技术执行SQL语句的过程：

  1 package hp.test;
  2 
  3 import java.io.File;
  4 import java.lang.reflect.Field;
  5 import java.lang.reflect.Method;
  6 import java.sql.Connection;
  7 import java.sql.DriverManager;
  8 import java.util.ArrayList;
  9 import java.util.Date;
 10 import java.util.List;
 11  
 12 
 13 
 14 
 15 
 16 import org.dom4j.Document;
 17 import org.dom4j.Element;
 18 import org.dom4j.io.SAXReader;
 19 
 20 import com.mysql.jdbc.PreparedStatement;
 21 
 22 public class MyHibernate
 23 {
 24     private class Column
 25     {
 26         private String name;
 27         private String length;
 28     }
 29     
 30     private class Generator
 31     {
 32         private String type;
 33     }
 34     
 35     private class Id
 36     {
 37         private String name;
 38         private String type;
 39         
 40         private Column column;
 41         private Generator generator;
 42     }
 43     private class Property
 44     {
 45         private String name;
 46         private String type;
 47         private Column column;
 48     }
 49     
 50     private class Class
 51     {
 52         private String name;
 53         private String table;
 54         private String catalog;
 55         
 56         private Id id;
 57         private List<Property> allProperties;
 58     }
 59     private class KeyValuePair
 60     {
 61         private String type;
 62         private Object value;
 63         
 64         private KeyValuePair(String type,Object value)
 65         {
 66             this.type = type;
 67             this.value = value;
 68         }
 69     }
 70     
 71     private String configPath ;
 72     private Object obj = null;
 73     private Document document;
 74     private Class voClass ;
 75     private String sql;
 76     private List<KeyValuePair> allValues;
 77     
 78     
 79     public MyHibernate(String configPath)
 80     {
 81         this.configPath = configPath;
 82     }
 83     
 84     public int save(Object obj) throws Exception
 85     {
 86         this.obj = obj; 
 87         this.load();
 88         this.format();
 89         this.generateSql();
 90         return this.saveToDb();
 91     }
 92     
 93     public void load() throws Exception
 94     {
 95         SAXReader saxReader = new SAXReader();
 96         this.document = saxReader.read(new File(this.configPath));
 97     }
 98     public void format() throws Exception
 99     {
100         Class _class = new Class();
101         org.dom4j.Element root = this.document.getRootElement();
102         Element classElement = root.element("class");
103         _class.name = classElement.attributeValue("name");
104         _class.table = classElement.attributeValue("table");
105         _class.catalog = classElement.attributeValue("catalog");
106         
107         Element idElement = classElement.element("id");
108         _class.id = new Id();
109         _class.id.name = idElement.attributeValue("name");
110         _class.id.type = idElement.attributeValue("type");
111         
112         Element columnElementInId = idElement.element("column");
113         _class.id.column = new Column();
114         _class.id.column.name = columnElementInId.attributeValue("name");
115         _class.id.column.length = columnElementInId.attributeValue("length");
116         
117         Element generatorElement = idElement.element("generator");
118         _class.id.generator = new Generator();
119         _class.id.generator.type =  generatorElement.attributeValue("class");
120         
121         List<Property> allProperties = new ArrayList<MyHibernate.Property>();
122         _class.allProperties = allProperties;
123         
124         List<Element> allPropertiesElements = classElement.elements("property");
125         for(Element item : allPropertiesElements)
126         {
127             Property property = new Property();
128             property.name = item.attributeValue("name");
129             property.type = item.attributeValue("type");
130             
131             Element columnElement = item.element("column");
132             property.column = new Column();
133             property.column.name = columnElement.attributeValue("name");
134             property.column.length = columnElement.attributeValue("length");
135             allProperties.add(property);
136             //System.out.println("name: " + property.name);
137         }
138         this.voClass = _class;
139     }
140     
141     public void generateSql() throws Exception
142     {
143         this.allValues = new ArrayList<MyHibernate.KeyValuePair>();
144         StringBuffer columns = new StringBuffer();
145         StringBuffer values = new StringBuffer();
146         StringBuffer sql = new StringBuffer(" INSERT INTO ");
147         sql.append(this.voClass.table).append("( ");
148         
149         if("assigned".equals(this.voClass.id.generator.type))
150         {
151             //需要用户提供主键列
152             columns.append(this.voClass.id.column.name).append(",");
153             values.append("?,");
154             
155             Field field = this.obj.getClass().getDeclaredField(this.voClass.id.name);
156             field.setAccessible(true);
157             this.allValues.add(new KeyValuePair(this.voClass.id.type, field.get(this.obj)));
158         }
159         
160         for(Property property : this.voClass.allProperties)
161         {
162             columns.append(property.column.name).append(",");
163             values.append("?,");
164             
165             Field field = this.obj.getClass().getDeclaredField(property.name);
166             field.setAccessible(true);
167             this.allValues.add(new KeyValuePair(property.type, field.get(this.obj)));
168         }
169         
170         columns.delete(columns.length()-1, columns.length());
171         values.delete(values.length()-1, columns.length());
172         
173         sql.append(columns.toString()).append(") VALUES (");
174         sql.append(values.toString()).append(")");
175         this.sql = sql.toString();
176         System.out.println(this.sql);
177     }
178     
179     public int saveToDb() throws Exception
180     {
181         java.lang.Class.forName("org.gjt.mm.mysql.Driver");
182         Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/hedb", "root", "admin");
183         java.sql.PreparedStatement ps = conn.prepareStatement(this.sql);
184         
185         for(int i = 0; i < this.allValues.size(); i++)
186         {
187             //System.out.println("***type:" + this.allValues.get(i).type);
188             if(String.class.getName().toString().equals(this.allValues.get(i).type))
189             {
190                 ps.setString(i+1, (String)this.allValues.get(i).value);
191             }
192             else if(Integer.class.getName().toString().equals(this.allValues.get(i).type))
193             {
194                 ps.setInt(i+1, (Integer)this.allValues.get(i).value);
195             }else if(Double.class.getName().toString().equals(this.allValues.get(i).type))
196             {
197                 ps.setDouble(i+1, (Double)this.allValues.get(i).value);
198             }else if(Date.class.getName().toString().equals(this.allValues.get(i).type))
199             {
200                 ps.setDate(i+1, new java.sql.Date(((Date)this.allValues.get(i).value).getTime()));
201             }
202             
203             //System.out.println("设置第" + (i+1) + "个值("+this.allValues.get(i).type+","+this.allValues.get(i).value+")");
204         }
205         return ps.executeUpdate();
206         
207     } 
208 }

测试代码：

 1 package hp.test;
 2 
 3 import java.util.Date;
 4 
 5 import org.hibernate.Session;
 6 import org.hibernate.SessionFactory; 
 7 
 8 import hp.pojo.Member;
 9 import hp.utils.HibernateHelper;
10 
11 public class Main
12 {
13 
14     public static void main(String[] args) 
15     {
16         Member vo = new Member();
17         vo.setMid("admin4");
18         vo.setAge(24);
19         vo.setBirthday(new Date());
20         vo.setName("sheldon4");
21         vo.setNote("a good person4");
22         vo.setSalary(44444.44);
23         
24         try
25         {
26             MyHibernate mh = new MyHibernate("C:\\D\\code\\resource\\mapping.xml"); 
27             int count = mh.save(vo);
28             System.out.println("成功插入" + count + "行数据");
29         }
30         catch(Exception e)
31         {
32             e.printStackTrace();
33             
34         }
35         System.out.println("main done//~");
36     }
37 
38 }