基于MyBatis注解扩展，实现无需配置即可使用

一、使用篇
如果项目本身基于SpringMVC+Mybatis构建，不需添加任何配置Mapper类只需继承BaseMapper，即拥有增删改方法操作，无需任何配置文件
1.

package com.springmvc.mapper;

import org.springframework.stereotype.Repository;

import com.nmtx.mybatis.ext.mapper.BaseMapper;
import com.springmvc.model.User;
@Repository
public interface UserMapper extends BaseMapper<User>{

}

2.

package com.springmvc.service.impl;

import javax.annotation.Resource;

import org.springframework.stereotype.Service;

import com.springmvc.mapper.UserMapper;
import com.springmvc.model.User;
import com.springmvc.service.UserService;

@Service
public class UserServiceImpl implements UserService{

@Resource
private UserMapper userMapper;

public int insertUser(User user) {
return userMapper.insert(user);
}

@Override
public int updateUser(User user) {
return userMapper.update(user);
}

@Override
public int deleteUser(User user) {
return userMapper.delete(user);
}

@Override
public User findUser(User user) {
return userMapper.findFirst(user);
}
}

3.

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.springmvc.mapper.UserMapper">

</mapper>

扩展原理基于Mybatis中 @InsertProvider，@DeleteProvider，@UpdateProvider，@SelectProvider注解，具体实现代码如下

1.

package com.nmtx.mybatis.ext.mapper;

import org.apache.ibatis.annotations.DeleteProvider;
import org.apache.ibatis.annotations.InsertProvider;
import org.apache.ibatis.annotations.Options;
import org.apache.ibatis.annotations.SelectProvider;
import org.apache.ibatis.annotations.UpdateProvider;

import com.nmtx.mybatis.ext.common.SqlProvider;

public interface BaseMapper<T> {

@InsertProvider(type = SqlProvider.class, method = "insert")
@Options(useGeneratedKeys=true)
public int insert(T bean);

@DeleteProvider(type = SqlProvider.class, method = "delete")
public int delete(T bean);

@UpdateProvider(type = SqlProvider.class, method = "update")
public int update(T bean);

@SelectProvider(type = SqlProvider.class, method = "findFirst")
public T findFirst(T bean);

2.

package com.nmtx.mybatis.ext.common;

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;

import org.apache.commons.lang3.ArrayUtils;
import org.springframework.util.StringUtils;

import com.nmtx.mybatis.ext.common.table.TableFormat;
import com.nmtx.mybatis.ext.common.table.annotation.Column;
import com.nmtx.mybatis.ext.common.table.annotation.Table;
import com.nmtx.mybatis.ext.common.table.impl.HumpToUnderLineFormat;

public class SqlProvider {

private TableFormat tableFormat = new HumpToUnderLineFormat();

public String insert(Object bean) {
Class<?> beanClass = bean.getClass();
String tableName = getTableName(beanClass);
Field[] fields = getFields(beanClass);
StringBuilder insertSql = new StringBuilder();
List<String> insertParas = new ArrayList<String>();
List<String> insertParaNames = new ArrayList<String>();
insertSql.append("INSERT INTO ").append(tableName).append("(");
try {
for (int i = 0; i < fields.length; i++) {
Field field = fields[i];
Column column = field.getAnnotation(Column.class);
String columnName = "";
if (column != null) {
if (!column.required())
continue;
columnName = column.value();
}
if (StringUtils.isEmpty(columnName)) {
columnName = tableFormat.getColumnName(field.getName());
}
field.setAccessible(true);
Object object = field.get(bean);
if (object != null) {
insertParaNames.add(columnName);
insertParas.add("#{" + field.getName() + "}");
}
}
} catch (Exception e) {
new RuntimeException("get insert sql is exceptoin:" + e);
}
for (int i = 0; i < insertParaNames.size(); i++) {
insertSql.append(insertParaNames.get(i));
if (i != insertParaNames.size() - 1)
insertSql.append(",");
}
insertSql.append(")").append(" VALUES(");
for (int i = 0; i < insertParas.size(); i++) {
insertSql.append(insertParas.get(i));
if (i != insertParas.size() - 1)
insertSql.append(",");
}
insertSql.append(")");
return insertSql.toString();
}

public String update(Object bean) {
Class<?> beanClass = bean.getClass();
String tableName = getTableName(beanClass);
Field[] fields = getFields(beanClass);
StringBuilder updateSql = new StringBuilder();
updateSql.append(" update ").append(tableName).append(" set ");
try {
for (int i = 0; i < fields.length; i++) {
Field field = fields[i];
Column column = field.getAnnotation(Column.class);
String columnName = "";
if (column != null) {
if (!column.required())
continue;
columnName = column.value();
}
if (StringUtils.isEmpty(columnName)) {
columnName = tableFormat.getColumnName(field.getName());
}
field.setAccessible(true);
Object beanValue = field.get(bean);
if (beanValue != null) {
updateSql.append(columnName).append("=#{").append(field.getName()).append("}");
if (i != fields.length - 1) {
updateSql.append(",");
}
}
}
} catch (Exception e) {
new RuntimeException("get update sql is exceptoin:" + e);
}
updateSql.append(" where ").append(tableFormat.getId()+" =#{id}");
return updateSql.toString();
}

public String delete(Object bean) {
Class<?> beanClass = bean.getClass();
String tableName = getTableName(beanClass);
Field[] fields = getFields(beanClass);
StringBuilder deleteSql = new StringBuilder();
deleteSql.append(" delete from ").append(tableName).append(" where  ");
try {
for (int i = 0; i < fields.length; i++) {
Field field = fields[i];
Column column = field.getAnnotation(Column.class);
String columnName = "";
if (column != null) {
if (!column.required())
continue;
columnName = column.value();
}
if (StringUtils.isEmpty(columnName)) {
columnName = tableFormat.getColumnName(field.getName());
}
field.setAccessible(true);
Object beanValue = field.get(bean);
if (beanValue != null) {
deleteSql.append(columnName).append("=#{").append(field.getName()).append("}");
if (i != fields.length - 1) {
deleteSql.append(" and ");
}
}
}
} catch (Exception e) {
new RuntimeException("get delete sql is exceptoin:" + e);
}
return deleteSql.toString();
}

public String findFirst(Object bean) {
Class<?> beanClass = bean.getClass();
String tableName = getTableName(beanClass);
Field[] fields = getFields(beanClass);
StringBuilder selectSql = new StringBuilder();
List<String> selectParaNames = new ArrayList<String>();
List<String> selectParas = new ArrayList<String>();
selectSql.append("select ");
try {
for (int i = 0; i < fields.length; i++) {
Field field = fields[i];
Column column = field.getAnnotation(Column.class);
String columnName = "";
if (column != null) {
if (!column.required())
continue;
columnName = column.value();
}
if (StringUtils.isEmpty(columnName)) {
columnName = tableFormat.getColumnName(field.getName());
}
field.setAccessible(true);
Object object = field.get(bean);
selectSql.append(field.getName());
if (object != null) {
selectParaNames.add(columnName);
selectParas.add("#{" + field.getName() + "}");
}
if (i != fields.length - 1)
selectSql.append(",");
}
} catch (Exception e) {
new RuntimeException("get select sql is exceptoin:" + e);
}
selectSql.append(" from ").append(tableName).append(" where ");
for (int i = 0; i < selectParaNames.size(); i++) {
selectSql.append(selectParaNames.get(i)).append("=").append(selectParas.get(i));
if (i != selectParaNames.size() - 1)
selectSql.append(" and ");
}
return selectSql.toString();
}

private String getTableName(Class<?> beanClass) {
String tableName = "";
Table table = beanClass.getAnnotation(Table.class);
if (table != null) {
tableName = table.value();
} else {
tableName = tableFormat.getTableName(beanClass.getSimpleName());
}
return tableName;
}

private Field[] getFields(Class<?> beanClass) {
Field[] beanFields = beanClass.getDeclaredFields();
Class<?> beanSuperClass = beanClass.getSuperclass();
Field[] beanSuperFields = beanSuperClass.getDeclaredFields();
return ArrayUtils.addAll(beanFields, beanSuperFields);
}
}