一、建造者模式.
1、MyBatis框架的环境类创建，通过静态内部类实现.
public final class Environment {
// 环境ID
private final String id;
// 事务工厂
private final TransactionFactory transactionFactory;
// 数据源
private final DataSource dataSource;
public Environment(String id, TransactionFactory transactionFactory, DataSource dataSource) {
// 1、构造方法中做一些必要的参数校验
if (id == null) {
throw new IllegalArgumentException("Parameter 'id' must not be null");
}
if (transactionFactory == null) {
throw new IllegalArgumentException("Parameter 'transactionFactory' must not be null");
}
this.id = id;
if (dataSource == null) {
throw new IllegalArgumentException("Parameter 'dataSource' must not be null");
}
this.transactionFactory = transactionFactory;
this.dataSource = dataSource;
}
// 2、静态内部类实现Builder
public static class Builder {
private String id;
private TransactionFactory transactionFactory;
private DataSource dataSource;
public Builder(String id) {
this.id = id;
}
public Builder transactionFactory(TransactionFactory transactionFactory) {
this.transactionFactory = transactionFactory;
return this;
}
public Builder dataSource(DataSource dataSource) {
this.dataSource = dataSource;
return this;
}
public String id() {
return this.id;
}
// 3、建造者
public Environment build() {
return new Environment(this.id, this.transactionFactory, this.dataSource);
}
}
public String getId() {
return this.id;
}
public TransactionFactory getTransactionFactory() {
return this.transactionFactory;
}
public DataSource getDataSource() {
return this.dataSource;
}
}使用方式：
2、Swagger的接口管理的建造者模式,通过外部类来实现.
// 定义接口管理基本信息
public ApiInfo(
String title,
String description,
String version,
String termsOfServiceUrl,
Contact contact,
String license,
String licenseUrl,
Collection<VendorExtension> vendorExtensions) {
this.title = title;
this.description = description;
this.version = version;
this.termsOfServiceUrl = termsOfServiceUrl;
this.contact = contact;
this.license = license;
this.licenseUrl = licenseUrl;
this.vendorExtensions = new ArrayList<>(vendorExtensions);
}
public String getTitle() {
return title;
}
public String getDescription() {
return description;
}
public String getTermsOfServiceUrl() {
return termsOfServiceUrl;
}
public Contact getContact() {
return contact;
}
public String getLicense() {
return license;
}
public String getLicenseUrl() {
return licenseUrl;
}
public String getVersion() {
return version;
}
public List<VendorExtension> getVendorExtensions() {
return vendorExtensions;
}
}// 定义建造者类
public class ApiInfoBuilder {
private String title;
private String description;
private String termsOfServiceUrl;
private Contact contact;
private String license;
private String licenseUrl;
private String version;
private final List<VendorExtension> vendorExtensions = new ArrayList<>();
/**
* Updates the api title
*
* @param title - title for the API
* @return this
*/
public ApiInfoBuilder title(String title) {
this.title = title;
return this;
}
/**
* Updates the api description
*
* @param description - api description
* @return this
*/
public ApiInfoBuilder description(String description) {
this.description = description;
return this;
}
/**
* Updates the terms of service url
*
* @param termsOfServiceUrl - url to the terms of service
* @return this
*/
public ApiInfoBuilder termsOfServiceUrl(String termsOfServiceUrl) {
this.termsOfServiceUrl = termsOfServiceUrl;
return this;
}
/**
* Updates the api version
*
* @param version - of the API
* @return this
*/
public ApiInfoBuilder version(String version) {
this.version = version;
return this;
}
/**
* Updates contact information for the person responsible for this API
*
* @param contact - contact information
* @return this
*/
public ApiInfoBuilder contact(Contact contact) {
this.contact = contact;
return this;
}
/**
* Updates license information for this API
*
* @param license licence string
* @return this
*/
public ApiInfoBuilder license(String license) {
this.license = license;
return this;
}
/**
* Updates the license Url for this API
*
* @param licenseUrl - license Url
* @return this
*/
public ApiInfoBuilder licenseUrl(String licenseUrl) {
this.licenseUrl = licenseUrl;
return this;
}
/**
* Adds extensions for this API
*
* @param extensions - extensions
* @return this
*/
public ApiInfoBuilder extensions(List<VendorExtension> extensions) {
this.vendorExtensions.addAll(nullToEmptyList(extensions));
return this;
}
public ApiInfo build() {
return new ApiInfo(title, description, version, termsOfServiceUrl, contact, license, licenseUrl, vendorExtensions);
}
}使用方式：
二、模板模板.
1、MyBatis的类型处理器的TypeHandler的实现.实现JavaType<->JdbcType的相互转换.
// 定义接口
public interface TypeHandler<T> {
void setParameter(PreparedStatement ps, int i, T parameter, JdbcType jdbcType) throws SQLException;
/**
* @param columnName Colunm name, when configuration <code>useColumnLabel</code> is <code>false</code>
*/
T getResult(ResultSet rs, String columnName) throws SQLException;
T getResult(ResultSet rs, int columnIndex) throws SQLException;
T getResult(CallableStatement cs, int columnIndex) throws SQLException;
}// 抽象类实现模板的公共逻辑和由子类要去实现的各自子逻辑
public abstract class BaseTypeHandler<T> extends TypeReference<T> implements TypeHandler<T> {
/**
* @deprecated Since 3.5.0 - See https://github.com/mybatis/mybatis-3/issues/1203. This field will remove future.
*/
@Deprecated
protected Configuration configuration;
/**
* @deprecated Since 3.5.0 - See https://github.com/mybatis/mybatis-3/issues/1203. This property will remove future.
*/
@Deprecated
public void setConfiguration(Configuration c) {
this.configuration = c;
}
@Override
public void setParameter(PreparedStatement ps, int i, T parameter, JdbcType jdbcType) throws SQLException {
if (parameter == null) {
if (jdbcType == null) {
throw new TypeException("JDBC requires that the JdbcType must be specified for all nullable parameters.");
}
try {
ps.setNull(i, jdbcType.TYPE_CODE);
} catch (SQLException e) {
throw new TypeException("Error setting null for parameter #" + i + " with JdbcType " + jdbcType + " . "
+ "Try setting a different JdbcType for this parameter or a different jdbcTypeForNull configuration property. "
+ "Cause: " + e, e);
}
} else {
try {
setNonNullParameter(ps, i, parameter, jdbcType);
} catch (Exception e) {
throw new TypeException("Error setting non null for parameter #" + i + " with JdbcType " + jdbcType + " . "
+ "Try setting a different JdbcType for this parameter or a different configuration property. "
+ "Cause: " + e, e);
}
}
}
@Override
public T getResult(ResultSet rs, String columnName) throws SQLException {
try {
return getNullableResult(rs, columnName);
} catch (Exception e) {
throw new ResultMapException("Error attempting to get column '" + columnName + "' from result set. Cause: " + e, e);
}
}
@Override
public T getResult(ResultSet rs, int columnIndex) throws SQLException {
try {
return getNullableResult(rs, columnIndex);
} catch (Exception e) {
throw new ResultMapException("Error attempting to get column #" + columnIndex + " from result set. Cause: " + e, e);
}
}
@Override
public T getResult(CallableStatement cs, int columnIndex) throws SQLException {
try {
return getNullableResult(cs, columnIndex);
} catch (Exception e) {
throw new ResultMapException("Error attempting to get column #" + columnIndex + " from callable statement. Cause: " + e, e);
}
}
public abstract void setNonNullParameter(PreparedStatement ps, int i, T parameter, JdbcType jdbcType) throws SQLException;
/**
* @param columnName Colunm name, when configuration <code>useColumnLabel</code> is <code>false</code>
*/
public abstract T getNullableResult(ResultSet rs, String columnName) throws SQLException;
public abstract T getNullableResult(ResultSet rs, int columnIndex) throws SQLException;
public abstract T getNullableResult(CallableStatement cs, int columnIndex) throws SQLException;
}
// 具体类实现父类的抽象逻辑即可.
public class IntegerTypeHandler extends BaseTypeHandler<Integer> {
@Override
public void setNonNullParameter(PreparedStatement ps, int i, Integer parameter, JdbcType jdbcType)
throws SQLException {
ps.setInt(i, parameter);
}
@Override
public Integer getNullableResult(ResultSet rs, String columnName)
throws SQLException {
int result = rs.getInt(columnName);
return result == 0 && rs.wasNull() ? null : result;
}
@Override
public Integer getNullableResult(ResultSet rs, int columnIndex)
throws SQLException {
int result = rs.getInt(columnIndex);
return result == 0 && rs.wasNull() ? null : result;
}
@Override
public Integer getNullableResult(CallableStatement cs, int columnIndex)
throws SQLException {
int result = cs.getInt(columnIndex);
return result == 0 && cs.wasNull() ? null : result;
}
}
