在使用mybatis的注解的形式的时候我们都希望能封装一些基础的方法。本篇内容就是基于此，本篇内容的源码
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BaseMapper如下：
/**
* 基础base
* @param <T>
* @param <K>
*/
public interface BaseMapper<T, K> {
/**
* 插入
* @param model
* @return
*/
@Lang(BaseMapperDriver.class)
@Insert({"<script>", "INSERT INTO ${table} ${values}", "</script>"})
@Options(useGeneratedKeys = true, keyColumn = "id", keyProperty = "id")
Long insert(T model);
/**
* 修改
* @param model
* @return
*/
@Lang(BaseMapperDriver.class)
@Update({"<script>", "UPDATE ${table} ${sets} WHERE ${id}=#{id}", "</script>"})
Long updateById(T model);
/**
* 删除
* @param id
* @return
*/
@Lang(BaseMapperDriver.class)
@Delete("DELETE FROM ${table} WHERE ${id}=#{id}")
Long deleteById(@Param("id") K id);
/**
* 根据ID获取
* @param id
* @return
*/
@Lang(BaseMapperDriver.class)
@Select("SELECT * FROM ${table} WHERE ${id}=#{id}")
T getById(@Param("id") K id);
/**
* 判断是否存在
* @param id
* @return
*/
@Lang(BaseMapperDriver.class)
@Select("SELECT COUNT(1) FROM ${table} WHERE ${id}=#{id}")
Boolean existById(@Param("id") K id);
}
为了不影响其他的SQL或者方法，这里自定义mybatis的语言：
BaseMapperDriver
具体实现如下：
/**
* 定义自定义的语言
* @author 大仙
*/
public class BaseMapperDriver extends XMLLanguageDriver implements LanguageDriver {
@Override
public SqlSource createSqlSource(Configuration configuration, String script, Class<?> parameterType) {
//获取当前mapper
Class<?> mapperClass = null;
if(configuration instanceof MybatisConfig){
mapperClass = MybatisMapperRegistry.getCurrentMapper();
}
if(mapperClass == null){
throw new RuntimeException("解析SQL出错");
}
//处理SQL
if(mapperClass!=null) {
Class<?>[] generics = getMapperGenerics(mapperClass);
Class<?> modelClass = generics[0];
Class<?> idClass = generics[1];
//表名
script = setTable(script, modelClass);
//主键
script = setId(script, modelClass);
//插入
script = setValues(script,modelClass);
//修改
script = setSets(script, modelClass);
//IN语句
script = setIn(script);
//单表查询结果映射，利用别名
script = setResultAlias(script,modelClass);
}
return super.createSqlSource(configuration, script, parameterType);
}
/**
* 获取泛型
* @param mapperClass
* @return
*/
private Class<?>[] getMapperGenerics(Class<?> mapperClass){
Class<?>[] classes = new Class[2];
Type[] types = mapperClass.getGenericInterfaces();
for(Type type:types){
ParameterizedType parameterizedType = (ParameterizedType)type;
Type[] types1 = parameterizedType.getActualTypeArguments();
classes[0] = (Class<?>) types1[0];
classes[1] = (Class<?>) types1[1];
}
return classes;
}
/**
* 设置表名
* @param script
* @param modelClass
* @return
*/
private String setTable(String script, Class<?> modelClass){
final Pattern inPattern = Pattern.compile("\\$\\{table\\}");
Matcher matcher = inPattern.matcher(script);
if (matcher.find()) {
//如果注解相同
if (modelClass.isAnnotationPresent(Table.class)) {
script = script.replaceAll("\\$\\{table\\}", modelClass.getAnnotation(Table.class).name());
} else {
System.out.println("=====" + modelClass.getSimpleName());
script = script.replaceAll("\\$\\{table\\}", CaseFormat.LOWER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, modelClass.getSimpleName()));
}
}
return script;
}
/**
* 替换ID
* @param script
* @param modelClass
* @return
*/
private String setId(String script,Class<?> modelClass){
final Pattern inPattern = Pattern.compile("\\$\\{id\\}");
Matcher matcher = inPattern.matcher(script);
if (matcher.find()) {
boolean exitIdEnum = false;
for (Field field : modelClass.getDeclaredFields()) {
if (field.isAnnotationPresent(Id.class)) {
script = script.replaceAll("\\$\\{id\\}", field.getAnnotation(Id.class).name());
exitIdEnum = true;
break;
}
}
if (!exitIdEnum) {
script = script.replaceAll("\\$\\{id\\}", "id");
}
}
return script;
}
/**
* 替换sets
* @param script
* @param modelClass
* @return
*/
private String setSets(String script,Class<?> modelClass){
final Pattern inPattern = Pattern.compile("\\$\\{sets\\}");
Matcher matcher = inPattern.matcher(script);
if (matcher.find()) {
StringBuffer ss = new StringBuffer();
ss.append("<set>");
//是否使用父类的属性
if(modelClass.isAnnotationPresent(UserParent.class)){
//获取父类
Class<?> superClass = modelClass.getSuperclass();
for(Field field : superClass.getDeclaredFields()){
//非public和protected的不处理
if(!(Modifier.isPublic(field.getModifiers())||Modifier.isProtected(field.getModifiers()))){
continue;
}
//如果不显示，直接返回
if (field.isAnnotationPresent(Invisiable.class)) {
continue;
}
//如果不显示，直接返回
if (field.isAnnotationPresent(Id.class)) {
continue;
}
//非驼峰命名规则
String temp = "<if test=\"__field != null\">__column=#{__field},</if>";
if(field.isAnnotationPresent(Column.class)){
ss.append(temp.replaceAll("__field", field.getName())
.replaceAll("__column",field.getAnnotation(Column.class).name() ));
continue;
}
//驼峰命名规则
ss.append(temp.replaceAll("__field", field.getName())
.replaceAll("__column", CaseFormat.LOWER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, field.getName())));
}
}
//本身
for (Field field : modelClass.getDeclaredFields()) {
//如果不显示，直接返回
if (field.isAnnotationPresent(Invisiable.class)) {
continue;
}
//如果不显示，直接返回
if (field.isAnnotationPresent(Id.class)) {
continue;
}
//非驼峰命名规则
String temp = "<if test=\"__field != null\">__column=#{__field},</if>";
if(field.isAnnotationPresent(Column.class)){
ss.append(temp.replaceAll("__field", field.getName())
.replaceAll("__column",field.getAnnotation(Column.class).name() ));
continue;
}
//驼峰命名规则
ss.append(temp.replaceAll("__field", field.getName())
.replaceAll("__column", CaseFormat.LOWER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, field.getName())));
}
ss.deleteCharAt(ss.lastIndexOf(","));
ss.append("</set>");
script = matcher.replaceAll(ss.toString());
}
return script;
}
/**
* 设置Value
* @param script
* @param modelClass
* @return
*/
private String setValues(String script,Class<?> modelClass){
final Pattern inPattern = Pattern.compile("\\$\\{values\\}");
Matcher matcher = inPattern.matcher(script);
if (matcher.find()) {
StringBuffer ss = new StringBuffer();
List<String> columns = new ArrayList<>();
List<String> values = new ArrayList<>();
//是否使用父类的属性
if(modelClass.isAnnotationPresent(UserParent.class)){
//获取父类
Class<?> superClass = modelClass.getSuperclass();
for(Field field : superClass.getDeclaredFields()){
//非public和protected的不处理
if(!(Modifier.isPublic(field.getModifiers())||Modifier.isProtected(field.getModifiers()))){
continue;
}
//如果不显示，直接返回
if (field.isAnnotationPresent(Invisiable.class)) {
continue;
}
//非驼峰命名规则
values.add("#{"+field.getName()+"}");
if(field.isAnnotationPresent(Column.class)){
columns.add(field.getAnnotation(Column.class).name() );
}else {
//驼峰命名规则
columns.add(CaseFormat.LOWER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, field.getName()));
}
}
}
//自身
for (Field field : modelClass.getDeclaredFields()) {
//如果不显示，直接返回
if (field.isAnnotationPresent(Invisiable.class)) {
continue;
}
//非驼峰命名规则
values.add("#{"+field.getName()+"}");
if(field.isAnnotationPresent(Column.class)){
columns.add(field.getAnnotation(Column.class).name() );
}else {
//驼峰命名规则
columns.add(CaseFormat.LOWER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, field.getName()));
}
}
ss.append("("+ StringUtils.join(columns.toArray(),",") +") VALUES ("+ StringUtils.join(values.toArray(),",")+")");
script = matcher.replaceAll(ss.toString());
}
return script;
}
/**
* in语句
* @param script
* @return
*/
private String setIn(String script){
final Pattern inPattern = Pattern.compile("\\$\\{ins\\}");
Matcher matcher = inPattern.matcher(script);
if (matcher.find()) {
script = matcher.replaceAll("(<foreach collection=\"$1\" item=\"__item\" separator=\",\" >#{__item}</foreach>)");
}
return script;
}
private String setResultAlias(String script,Class<?> modelClass){
return script;
}
}
那么其中的注解等内容请自行阅读源码，这里讲解核心的当前mapper获取的方法。我们自定义MapperRegistry，重写他的addMapper的方法，捕获当前mapper，并存储，并在使用完成之后进行丢弃。
/**
* 自定义mapperRegistry
* @author 大仙
*/
public class MybatisMapperRegistry extends MapperRegistry {
private final Map<Class<?>, MapperProxyFactory<?>> knownMappers = new HashMap();
private Configuration config;
private static Class<?> currentMapper;
public MybatisMapperRegistry(Configuration config) {
super(config);
this.config = config;
}
@Override
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory)this.knownMappers.get(type);
if (mapperProxyFactory == null) {
throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
} else {
try {
return mapperProxyFactory.newInstance(sqlSession);
} catch (Exception var5) {
throw new BindingException("Error getting mapper instance. Cause: " + var5, var5);
}
}
}
@Override
public <T> boolean hasMapper(Class<T> type) {
return this.knownMappers.containsKey(type);
}
@Override
public <T> void addMapper(Class<T> type) {
if (type.isInterface()) {
if (this.hasMapper(type)) {
throw new BindingException("Type " + type + " is already known to the MapperRegistry.");
}
boolean loadCompleted = false;
try {
this.knownMappers.put(type, new MapperProxyFactory(type));
MapperAnnotationBuilder parser = new MapperAnnotationBuilder(this.config, type);
currentMapper = type;
parser.parse();
currentMapper=null;
loadCompleted = true;
} finally {
if (!loadCompleted) {
this.knownMappers.remove(type);
}
}
}
}
@Override
public Collection<Class<?>> getMappers() {
return Collections.unmodifiableCollection(this.knownMappers.keySet());
}
@Override
public void addMappers(String packageName, Class<?> superType) {
ResolverUtil<Class<?>> resolverUtil = new ResolverUtil();
resolverUtil.find(new ResolverUtil.IsA(superType), packageName);
Set<Class<? extends Class<?>>> mapperSet = resolverUtil.getClasses();
Iterator var5 = mapperSet.iterator();
while(var5.hasNext()) {
Class<?> mapperClass = (Class)var5.next();
this.addMapper(mapperClass);
}
}
@Override
public void addMappers(String packageName) {
this.addMappers(packageName, Object.class);
}
public static Class<?> getCurrentMapper() {
return currentMapper;
}
}
讲该类，配置到config类中。
/**
* 重写mybatis的configureation
* @author 大仙
*/
public class MybatisConfig extends Configuration {
protected final MapperRegistry mapperRegistry;
public MybatisConfig(){
super();
this.mapperRegistry = new MybatisMapperRegistry(this);
this.mapUnderscoreToCamelCase = true;
}
@Override
public MapperRegistry getMapperRegistry() {
return this.mapperRegistry;
}
@Override
public void addMappers(String packageName, Class<?> superType) {
this.mapperRegistry.addMappers(packageName, superType);
}
@Override
public void addMappers(String packageName) {
this.mapperRegistry.addMappers(packageName);
}
@Override
public <T> void addMapper(Class<T> type) {
this.mapperRegistry.addMapper(type);
}
@Override
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
return this.mapperRegistry.getMapper(type, sqlSession);
}
@Override
public boolean hasMapper(Class<?> type) {
return this.mapperRegistry.hasMapper(type);
}
}
使自定义的config类生效，我这里用的sharding-jdbc做的读写分离，不使用也是一样的配置，初始化SQLSessionFactory并制定config类即可
@Bean
@Primary
public SqlSessionFactory sqlSessionFactory() throws Exception {
SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
bean.setDataSource(masterSlaveDataSource());
bean.setConfiguration(new MybatisConfig());
return bean.getObject();
}
来源：CSDN
作者：zhuwei_clark
链接：https://blog.csdn.net/zhuwei_clark/article/details/104637566