java 根据实体对象生成 增删改的SQL语句 ModelToSQL

原文链接

在参考原文链接的代码后,发现有一处小错误,就是update 的set 两个条件之间差 逗号,于是乎自己小小的修改了下,并且加了部分代码的注释,最终代码如下:

package com.xxx.utils;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.List;
import java.util.Vector;

import org.apache.commons.lang3.reflect.FieldUtils;

public class ModelToSQL {
private Object target;

private String idName;

private Object idValue;

private SqlType currentType;

public enum SqlType {
INSERT, UPDATE, DELETE
}

public ModelToSQL(SqlType sqlType, Object target) {
this.target = target;
switch (sqlType) {
case INSERT:
currentType = SqlType.INSERT;
createInsert();
break;
case UPDATE:
currentType = SqlType.UPDATE;
createUpdate();
break;
case DELETE:
currentType = SqlType.DELETE;
createDelete();
break;
}
}

public ModelToSQL(Class<?> target) {
String tableName = getTableNameForClass(target);
getFields(target);

StringBuffer sqlBuffer = new StringBuffer();
sqlBuffer.append("DELETE FROM ").append(tableName).append(" WHERE ");
for (Field field : fields) {
if (!Modifier.isStatic(field.getModifiers())) {
ID id = field.getAnnotation(ID.class);
if (null != id) {
sqlBuffer.append(field.getName()).append("=?");
}
}
}
this.sqlBuffer = sqlBuffer.toString();
}

/**
* 创建跟删除
*/
private void createDelete() {
String tableName = getTableName();
getFields(target.getClass());
StringBuffer sqlBuffer = new StringBuffer();
sqlBuffer.append("DELETE FROM ").append(tableName).append(" WHERE ");
for (Field field : fields) {
if (!Modifier.isStatic(field.getModifiers())) {
ID id = field.getAnnotation(ID.class);
if (null != id) {
sqlBuffer.append(field.getName()).append(" = ? ");
param.add(readField(field));
}
}
}
System.err.println("delete:\t"+sqlBuffer.toString());
this.sqlBuffer = sqlBuffer.toString();
}

protected Object readField(Field field) {
try {
return FieldUtils.readField(field, target, true);
} catch (Exception e) {
throw new RuntimeException(currentType.name(), e);
}
}

/**
* 创建更新语句
*/
private void createUpdate() {
String tableName = getTableName();
getFields(target.getClass());
StringBuffer sqlBuffer = new StringBuffer();
sqlBuffer.append("UPDATE ").append(tableName).append(" SET ");

for (Field field : fields) {
if (!Modifier.isStatic(field.getModifiers())) {
ID id = field.getAnnotation(ID.class);
if (id == null) {
sqlBuffer.append(field.getName()).append("=? , ");
param.add(readField(field));
} else {
idName = field.getName();
idValue = readField(field);
}
}
}
sqlBuffer.replace(sqlBuffer.length()-2, sqlBuffer.length()-1, " ");
if (idName == null) {
throw new RuntimeException("not found of " + target.getClass() + "'s ID");
}
sqlBuffer.append(" WHERE ").append(idName).append("=?");
param.add(idValue);
System.err.println("update:\t"+sqlBuffer.toString());
this.sqlBuffer = sqlBuffer.toString();
}

/**
* 根据注解获取表名
*/
private String getTableName() {
String tableName = null;
Class<?> clazz = target.getClass();
tableName = getTableNameForClass(clazz);
return tableName;
}

private String getTableNameForClass(Class<?> clazz) {
String tableName;
Table table = clazz.getAnnotation(Table.class);
if (null != table) {
tableName = table.name();
if ("".equalsIgnoreCase(tableName)) {
tableName = clazz.getSimpleName();
}
} else {
tableName = clazz.getSimpleName();
}
return tableName;
}

/**
* 创建插入语句
*/
private void createInsert() {
String tableName = getTableName();
getFields(target.getClass());
StringBuffer sqlBuffer = new StringBuffer();
sqlBuffer.append("INSERT INTO ").append(tableName).append("(");

for (Field field : fields) {
if (!Modifier.isStatic(field.getModifiers())) {
ID id = field.getAnnotation(ID.class);
if (id == null) {
sqlBuffer.append(field.getName()).append(",");
param.add(readField(field));
}
}
}
int length = sqlBuffer.length();
sqlBuffer.delete(length - 1, length).append(")values(");
int size = param.size();
for (int x = 0; x < size; x++) {
if (x != 0) {
sqlBuffer.append(",");
}
sqlBuffer.append("?");
}
sqlBuffer.append(")");
System.err.println("insert:\t"+sqlBuffer.toString());
this.sqlBuffer = sqlBuffer.toString();
}

private List<Object> param = new Vector<Object>();

private String sqlBuffer;

public List<Object> getParam() {
return param;
}

public String getSqlBuffer() {
return sqlBuffer;
}

public String getIdName() {
return idName;
}

public Object getIdValue() {
return idValue;
}

List<Field> fields = new Vector<Field>();

protected void getFields(Class<?> clazz) {
if (Object.class.equals(clazz)) {
return;
}
Field[] fieldArray = clazz.getDeclaredFields();
for (Field file : fieldArray) {
fields.add(file);
}
getFields(clazz.getSuperclass());
}

//创建注解,标识该model的table名
@java.lang.annotation.Target(value = { java.lang.annotation.ElementType.TYPE })
@java.lang.annotation.Retention(value = java.lang.annotation.RetentionPolicy.RUNTIME)
public @interface Table {
String name() default "";
}

//创建注解,标识该model的id字段
@java.lang.annotation.Target(value = { java.lang.annotation.ElementType.FIELD })
@java.lang.annotation.Retention(value = java.lang.annotation.RetentionPolicy.RUNTIME)
public @interface ID {
}
}

model

package test.xxx.utils;

@Table(name="Student")
public class TestModel {

@ID
private int sid;
private  String name;
private int age ;
public int getSid() {
return sid;
}
public void setSid(int sid) {
this.sid = sid;
}
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;
}

}

测试

public class Test {
public static void main(String[] args) {
new ModelToSQL(SqlType.INSERT, new TestModel());
new ModelToSQL(SqlType.UPDATE, new TestModel());
new ModelToSQL(SqlType.DELETE, new TestModel());
}

}

生成的sql语句

insert: INSERT INTO Student(name,age)values(?,?)
update: UPDATE Student SET name=? , age=?    WHERE sid=?
delete: DELETE FROM Student WHERE sid = ?

用到的jar包的maven地址如下

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-lang3 -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.0</version>
</dependency>