SSM框架（七）Sping框架之SQL【Generator代码生成器】原理
目录
- 一、Generator代码生成器有什么用？
- 二、SQLGenerator.java示例
- (1) 目录结构
- (2)实体+注解
- (3)Generator代码生成器
- 三、完整SQLGenerator.java
前面SSM（四）模仿sping-mvc自定义一个框架中：
最后讲到：Sping框架通用SQLGenerator.java
一、Generator代码生成器有什么用？
条件：1、我们需要对两张 表做增删查改操作 2、如果需要对无数张 表进行增删查改操作；
思考：我们是不是要针对不同表在代码里一条一条写出查询语句？
@param o->UserInfo(id,name)
@return select * from user_info where user_id = ? and user_name = ?;
@param o->StudentInfo(id,name,number)
@return select * from t_student where t_stuid = ? and t_stuname = ? and t_stunumber = ?
由上述sql语句我们可以总结出：
SELECT column_name,column_name
FROM table_name
WHERE some_column=some_value;;
于是，我们采用Generator代码生成器，自动生成sql语句,不需要我们每次写出完整的增删查改。
二、SQLGenerator.java示例
(1) 目录结构
下面用一个demo示例演示以上三种功能：
(2)实体+注解
（注解标签使用方法参考：SSM框架（四）-注解部分）
在Column和Table两个接口里定义了2类注解：
- @Retention : 元注解 --生命周期在运行时
- @Target ：注解可以用在类/接口，方法、字段上
-》 定义一个UserInfo类和一个student类，写main函数测试结果如下：
（运行时类引用了Table接口、每个元素与（数据库）这里我们与Column相联系）
UserInfo:
package com.cungudafa.annotation.demo;
@Table("user_info")
public class UserInfo {//user_info表
@Column("user_id")
private Integer userId;//user_id字段
@Column("user_name")
private String userName;//user_name字段
public Integer getUserId() {
return userId;
}
public void setUserId(Integer userId) {
this.userId = userId;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
}
StudentInfo:
package com.cungudafa.annotation.demo;
@Table("t_student")
public class StudentInfo {
@Column("t_stuid")
private Integer id;
@Column("t_stuname")
private String studentName;
@Column("t_stunumber")
private String studentNumber;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getStudentName() {
return studentName;
}
public void setStudentName(String studentName) {
this.studentName = studentName;
}
public String getStudentNumber() {
return studentNumber;
}
public void setStudentNumber(String studentNumber) {
this.studentNumber = studentNumber;
}
}
(3)Generator代码生成器
定义SQLGenerator.java：
- 模拟数据库请求操作时，对sql语句变量的控制
例：select * from user_info where 1=1 and user_name = 'zhangsan' and user_id = 10001
select * from 表名 where 直接写入条件 and 查询关键词1 = '字符串' and 查询关键词2 = 数字package com.cungudafa.annotation.demo; import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.ArrayList; import java.util.List; /** * 生成SQL * @author Administrator * */ public class SQLGenerator { public static String createInsertSql(Object o){ return null;//待补充 } public static String createDeleteSql(Object o){ return null; } public static String createUpdateSql(Object o){ return null; } /** * * @param o->UserInfo(id,name) * @return select * from user_info where user_id = ? and user_name = ?; * @throws InvocationTargetException * @throws IllegalArgumentException * @throws IllegalAccessException * @throws SecurityException * @throws NoSuchFieldException */ public static String createSelectSql(Object o) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchFieldException, SecurityException{ //获取传入对象的运行时类 Class c = o.getClass(); //判断该类是否有@Table注解 if(c.isAnnotationPresent(Table.class)){ String sql = "select * from "; Table t = (Table) c.getAnnotation(Table.class); String tableName = t.value(); sql = sql + tableName + " where 1=1 "; //获取所有的get方法 Method[] methods = c.getDeclaredMethods(); List<Method> getMethods = new ArrayList<>(); for(Method method : methods){ if(method.getName().startsWith("get")){ getMethods.add(method); } } //遍历get方法 for(Method method : getMethods){ Object value = method.invoke(o); if(value != null){ String methodName = method.getName();//getUserId/getUserName System.out.println("methodName = " + methodName); //getUserId-->userId String fieldName = methodName.replaceAll("get", "");//UserId fieldName = fieldName.substring(0, 1).toLowerCase() + fieldName.substring(1);//UserId->userId System.out.println("fieldName = " + fieldName); //获得字段 Field field = c.getDeclaredField(fieldName); System.out.println("field = " + field); //判断字段上是否有Column注解 if(field.isAnnotationPresent(Column.class)){ //获得字段上的Column注解 Column col = field.getAnnotation(Column.class); //获得注解的value值，作为列名 String columnName = col.value(); if(value instanceof Integer){//区分id学号String转int（数据库为int） sql = sql + "and " + columnName + " = " + String.valueOf(value) + " "; }else{ sql = sql + "and " + columnName + " = '" + String.valueOf(value) + "' "; } } } } return sql; }else{ return null; } } }
-》 测试结果：（两张表都可以通用SQLGenerator框架）
sql = select * from user_info where 1=1 and user_name = ‘zhangsan’ and user_id = 10001
sql = select * from t_student where 1=1 and t_stuid = 10002 and t_stuname = ‘李四’ and t_stunumber = ‘102001203103’
三、完整SQLGenerator.java
自定义SQLGenerator：
package com.cungudafa.annotation.demo;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import javax.swing.filechooser.FileNameExtensionFilter;
/**
* 生成SQL
* @author Administrator
*
*/
public class SQLGenerator {
/**
* 插入
* @param o->UserInfo(id,name)
* @return insert into t_student vlaues (?, ?, ?)
* @throws InvocationTargetException
* @throws IllegalArgumentException
* @throws IllegalAccessException
* @throws SecurityException
* @throws NoSuchFieldException
*/
public static String createInsertSql(Object o) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchFieldException, SecurityException{
//获取传入对象的运行时类
Class c = o.getClass();
//判断该类是否有@Table注解
if(c.isAnnotationPresent(Table.class)){
String sql = "insert into ";
Table t = (Table) c.getAnnotation(Table.class);
String tableName = t.value();
sql = sql + tableName + " vlaues (";
//获取所有的get方法
Method[] methods = c.getDeclaredMethods();
List<Method> getMethods = new ArrayList<>();
for(Method method : methods){
if(method.getName().startsWith("get")){
getMethods.add(method);
}
}
//遍历get方法
for(Method method : getMethods){
Object value = method.invoke(o);
if(value != null){
String methodName = method.getName();//getUserId/getUserName
//System.out.println("methodName = " + methodName);
//getUserId-->userId
String fieldName = methodName.replaceAll("get", "");//UserId
fieldName = fieldName.substring(0, 1).toLowerCase() + fieldName.substring(1);//UserId->userId
//System.out.println("fieldName = " + fieldName);
//获得字段
Field field = c.getDeclaredField(fieldName);
//System.out.println("field = " + field);
//判断字段上是否有Column注解
if(field.isAnnotationPresent(Column.class)){
//获得字段上的Column注解
Column col = field.getAnnotation(Column.class);
//获得注解的value值，作为列名
String columnName = col.value();
if(value instanceof Integer){//区分id学号String转int（数据库为int）
sql = sql + String.valueOf(value) + ",";
}else{
sql = sql +" '" + String.valueOf(value) + "',";
}
}
}
}
sql = sql.substring(0,sql.length()-1) + ")";//删去sql句末多余的“,”
return sql;
}else{
return null;
}
}
/**
* 删除
* @param o->UserInfo(id,name)
* @return DELETE FROM t_student where and t_stuid = ?
* @throws InvocationTargetException
* @throws IllegalArgumentException
* @throws IllegalAccessException
* @throws SecurityException
* @throws NoSuchFieldException
*/
public static String createDeleteSql(Object o) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchFieldException, SecurityException{
//获取传入对象的运行时类
Class c = o.getClass();
//判断该类是否有@Table注解
if(c.isAnnotationPresent(Table.class)){
String sql = "DELETE FROM ";
Table t = (Table) c.getAnnotation(Table.class);
String tableName = t.value();
sql = sql + tableName + " where ";
//获取所有的get方法
Method[] methods = c.getDeclaredMethods();
List<Method> getMethods = new ArrayList<>();
for(Method method : methods){
if(method.getName().startsWith("get")){
getMethods.add(method);
}
}
//遍历get方法
for(Method method : getMethods){
Object value = method.invoke(o);
if(value != null){
String methodName = method.getName();//getUserId/getUserName
//System.out.println("methodName = " + methodName);
//getUserId-->userId
String fieldName = methodName.replaceAll("get", "");//UserId
fieldName = fieldName.substring(0, 1).toLowerCase() + fieldName.substring(1);//UserId->userId
//System.out.println("fieldName = " + fieldName);
//获得字段
Field field = c.getDeclaredField(fieldName);
//System.out.println("field = " + field);
//判断字段上是否有Column注解
if(field.isAnnotationPresent(Column.class)){
//获得字段上的Column注解
Column col = field.getAnnotation(Column.class);
//获得注解的value值，作为列名
String columnName = col.value();
if(value instanceof Integer){//区分id学号String转int（数据库为int）
sql = sql + columnName + " = " + String.valueOf(value) + " and ";
}else{
sql = sql + columnName + " = '" + String.valueOf(value) + "' and ";
}
}
}
}
sql=sql.substring(0,sql.length()-4);//删去sql句末多余的“and ”
return sql;
}else{
return null;
}
}
/**
* 更新
* @param o->UserInfo(id,name)
* @return UPDATE table_name
SET column1=value1,column2=value2,...
WHERE some_column=some_value;
* @throws InvocationTargetException
* @throws IllegalArgumentException
* @throws IllegalAccessException
* @throws SecurityException
* @throws NoSuchFieldException
*/
public static String createUpdateSql(Object o,Object o1) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchFieldException, SecurityException{
//获取传入对象的运行时类
Class c = o.getClass();
Class c1 = o1.getClass();
//判断该类是否有@Table注解
if(c.isAnnotationPresent(Table.class)){
String sql = "update ";
Table t = (Table) c.getAnnotation(Table.class);
String tableName = t.value();
sql = sql + tableName + " set ";
//获取所有的get方法
Method[] methods = c.getDeclaredMethods();
List<Method> getMethods = new ArrayList<>();
for(Method method : methods){
if(method.getName().startsWith("get")){
getMethods.add(method);
}
}
//遍历get方法
for(Method method : getMethods){
Object value = method.invoke(o1);
if(value != null){
String methodName = method.getName();//getUserId/getUserName
//System.out.println("methodName = " + methodName);
//getUserId-->userId
String fieldName = methodName.replaceAll("get", "");//UserId
fieldName = fieldName.substring(0, 1).toLowerCase() + fieldName.substring(1);//UserId->userId大写转小写
//System.out.println("fieldName = " + fieldName);
//获得字段
Field field = c.getDeclaredField(fieldName);
//System.out.println("field = " + field);
//判断字段上是否有Column注解
if(field.isAnnotationPresent(Column.class)){
//获得字段上的Column注解
Column col = field.getAnnotation(Column.class);
//获得注解的value值，作为列名
String columnName = col.value();
if(value instanceof Integer){//区分id学号String转int（数据库为int）
sql = sql + columnName + " = " + String.valueOf(value) + " and ";
}else{
sql = sql + columnName + " = '" + String.valueOf(value) + "' and ";
}
}
}
}
sql = sql.substring(0,sql.length()-4)+"where ";//删去sql句末多余的“and ”
//获取所有的get方法
methods = c.getDeclaredMethods();
getMethods = new ArrayList<>();
for(Method method : methods){
if(method.getName().startsWith("get")){
getMethods.add(method);
}
}
//遍历get方法
for(Method method : getMethods){
Object value = method.invoke(o);
if(value != null){
String methodName = method.getName();//getUserId/getUserName
//System.out.println("methodName = " + methodName);
//getUserId-->userId
String fieldName = methodName.replaceAll("get", "");//UserId
fieldName = fieldName.substring(0, 1).toLowerCase() + fieldName.substring(1);//UserId->userId
//System.out.println("fieldName = " + fieldName);
//获得字段
Field field = c.getDeclaredField(fieldName);
//System.out.println("field = " + field);
//判断字段上是否有Column注解
if(field.isAnnotationPresent(Column.class)){
//获得字段上的Column注解
Column col = field.getAnnotation(Column.class);
//获得注解的value值，作为列名
String columnName = col.value();
if(value instanceof Integer){//区分id学号String转int（数据库为int）
sql = sql + columnName + " = " + String.valueOf(value) + " and ";
}else{
sql = sql + columnName + " = '" + String.valueOf(value) + "' and ";
}
}
}
}
sql = sql.substring(0,sql.length()-4);
return sql;
}else{
return null;
}
}
/**
* 查询
* @param o->UserInfo(id,name)
* @return select * from user_info where user_id = ? and user_name = ?;
* @throws InvocationTargetException
* @throws IllegalArgumentException
* @throws IllegalAccessException
* @throws SecurityException
* @throws NoSuchFieldException
*/
public static String createSelectSql(Object o) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchFieldException, SecurityException{
//获取传入对象的运行时类
Class c = o.getClass();
//判断该类是否有@Table注解
if(c.isAnnotationPresent(Table.class)){
String sql = "select * from ";
Table t = (Table) c.getAnnotation(Table.class);
String tableName = t.value();
sql = sql + tableName + " where 1=1 ";
//获取所有的get方法
Method[] methods = c.getDeclaredMethods();
List<Method> getMethods = new ArrayList<>();
for(Method method : methods){
if(method.getName().startsWith("get")){
getMethods.add(method);
}
}
//遍历get方法
for(Method method : getMethods){
Object value = method.invoke(o);
if(value != null){
String methodName = method.getName();//getUserId/getUserName
System.out.println("methodName = " + methodName);
//getUserId-->userId
String fieldName = methodName.replaceAll("get", "");//UserId
fieldName = fieldName.substring(0, 1).toLowerCase() + fieldName.substring(1);//UserId->userId
System.out.println("fieldName = " + fieldName);
//获得字段
Field field = c.getDeclaredField(fieldName);
System.out.println("field = " + field);
//判断字段上是否有Column注解
if(field.isAnnotationPresent(Column.class)){
//获得字段上的Column注解
Column col = field.getAnnotation(Column.class);
//获得注解的value值，作为列名
String columnName = col.value();
if(value instanceof Integer){//区分id学号String转int（数据库为int）
sql = sql + "and " + columnName + " = " + String.valueOf(value) + " ";
}else{
sql = sql + "and " + columnName + " = '" + String.valueOf(value) + "' ";
}
}
}
}
return sql;
}else{
return null;
}
}
}
- 测试main函数：
TestCase：
package com.cungudafa.annotation.demo;
import java.lang.reflect.InvocationTargetException;
public class TestCase {
public static void main(String[] args) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchFieldException, SecurityException {
UserInfo userInfo = new UserInfo();
userInfo.setUserId(10001);
userInfo.setUserName("zhangsan");
String sql = SQLGenerator.createSelectSql(userInfo);
System.out.println("sql = " + sql);
System.out.println("--------查询-----------");
StudentInfo s = new StudentInfo();
s.setId(10002);
s.setStudentName("李四");
s.setStudentNumber("102001203103");
sql = SQLGenerator.createSelectSql(s);
System.out.println("--------查询-----------");
System.out.println("sql = " + sql);
System.out.println("--------插入-----------");
StudentInfo s1 = new StudentInfo();
s1.setId(10002);//插入内容
s1.setStudentName("李四");
s1.setStudentNumber("102001203103");
sql = SQLGenerator.createInsertSql(s1);
System.out.println("sql = " + sql);
System.out.println("--------删除-----------");
StudentInfo s2 = new StudentInfo();
s2.setId(10002);//删除条件任取
s2.setStudentName("李四");
s2.setStudentNumber("102001203103");
sql = SQLGenerator.createDeleteSql(s2);
System.out.println("sql = " + sql);
System.out.println("--------更新studentinfo-----------");
StudentInfo s3 = new StudentInfo();
s3.setId(10002);//默认s3内容
s3.setStudentName("李四");
s3.setStudentNumber("102001203103");
//修改内容
StudentInfo s3_update = new StudentInfo();
//s3_update.setId(s3.getId());//获得原始id,id唯一不可更改
s3_update.setStudentName("张三");
s3_update.setStudentNumber("0123456789");
sql = SQLGenerator.createUpdateSql(s3,s3_update);
System.out.println("sql = " + sql);
System.out.println("\n--------userinfo表：-----------");
UserInfo userInfo1 = new UserInfo();
userInfo1.setUserId(1001);
userInfo1.setUserName("user001");
sql = SQLGenerator.createSelectSql(userInfo1);
System.out.println("\nSelectsql = " + sql);//查
sql = SQLGenerator.createInsertSql(userInfo1);
System.out.println("\nInsertsql = " + sql);//增
userInfo1.setUserName("user123");//修改姓名
sql = SQLGenerator.createUpdateSql(userInfo,userInfo1);//user001->user123
System.out.println("\nUpdatesql = " + sql);//改
sql = SQLGenerator.createDeleteSql(userInfo1);
System.out.println("\nDeletesql = " + sql);//删
}
}
- 结果：
